Author Topic: furnace vs heat pump decision (Read 5103 times)

sol

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furnace vs heat pump decision
« on: April 22, 2017, 02:38:27 PM »
Should I replace my gas furnace with a heat pump? I live in the coastal PNW, in a pretty moderate climate.

Nerd alert: I've kept pretty good records of our natural gas consumption, which averages about 450 therms per year total. Approximately 160 of that goes to our hot water heater (calculated by looking at summertime gas usage when the furnace is off and extrapolating out for the whole year). So that means we consume 290 therms to heat our house, for about six months of the year. We pay 88 cents per therm (including delivery charges), which means we spend 0.88*290= $255/year to heat our home with natural gas. That seems cheap, to me.

Our current gas furnace is a 20 year old 80% AFUE single stage unit, which means approximately 20% of the natural gas we buy goes up the chimney instead of into heating the house. In effect, this means our home really only needs 80% of those 290 therms, or 232 therms, to stay warm if we were 100% efficient. Unfortunately, upgrading to a 95% AFUE furnace isn't really cost effective for us, because it would only reduce our heating gas use from 290 to 251 therms, for a savings of $34/year. Big whoop.

Electrical heating (baseboards) are 100% efficient. If my house really requires 232 therms to stay warm, and the internet suggest that one therm is worth 29.3 kWh, then we could theoretically stay warm by using another 6798 kWh of electricity. At 7.41 cents per kWh, that would cost us $504/year. That's more than we currently pay for gas, which doesn't surprise me because baseboards are widely thought to be more expensive than gas heat.

But heat pumps are more than 100% efficient, because they are relocating heat from outside to inside instead of generating it by resistance. Around here, heat pumps reportedly average between 200% and 300% efficiency, so that reduces the power cost from $504/year to somewhere between $252/year (worst case, 200% efficient) and $168/year (best case, 300% efficient). I think.

So at the very least, it looks like switching to a heat pump is unlikely to cost us MORE per year to heat the house, other than the installation cost. This is an urgent decision, because we're adding a central air conditioner to our house (for several thousand dollars) and it's approximately $400 in added cost to put in a heat pump instead of an AC unit, since the two are apparently nearly identical mechanical objects with the addition of a reversing valve so it can pump heat out of OR into your house, depending on the season.

Other considerations:
1. heat pumps don't blast you with hot air the way a gas furnace does. They run more often, more quietly, delivering lower volumes of warm air instead of a blast of hot air that makes my dog lay next to the register on cold days. Right now, I can get home and have my house fully warm in less than 10 minutes.
2. heat pumps (and AC) units don't last as long as gas furnaces. Maybe 15 years, instead of 25?
3. We have solar panels, but they don't really figure into this calculation because we're grid tied and still "pay" for all of the power we use, either by buying it from the utility company or by not selling it to the utility company.
4. The house already has ducting and venting and an active gas line, and it seems a little silly to not use those advantages.
5. The lowest cost up-front option is to just add the AC to our existing 20 year old gas furnace, but it will need replacing eventually and doing it now as part of an AC install is cheaper than doing it next year as a separate job.
6. There is a slight eco-smugness benefit to going full electric with a heat pump, to reduce my family's carbon consumption.

Do any of you have experience with heat pumps in similar climates? How do you like it? What do you think I should do?
« Last Edit: April 22, 2017, 02:40:35 PM by sol »

Spork

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Re: furnace vs heat pump decision
« Reply #1 on: April 22, 2017, 02:54:06 PM »
I'll give my my experience, but I feel like it comes with a HUGE set of caveats:

* This was about 1990. I suspect everything has changed since then. I am sure they are more efficient. My house was low end builder grade... and I am sure it was the low end of what was available even back then.
* Let's be frank -- I wasn't very mustacian back then. I was just out of school and was probably a lot less tolerant than I would be now of a trade-off of comfort vs cost.

---

That said: Back then, I didn't like the heat pump. I had grown up with cozy warm gas furnaces and I thought it was drafty and cold feeling. Ours did have secondary heat (a resistance coil) that kicked in if you wanted to warm it faster. If you wanted to warm it a couple of degrees: heat pump. If you turned the thermostat 8-10 degrees warmer: heat pump AND heat coil. My perception at the time was that the heat pump was more expensive to run than gas. I'm unsure if that was true then or not.

Current date: I have (super expensive) propane heat as a secondary but mostly use a wood stove. The cold corners of my house are clearly colder than they were back in the 1990s. And I run the HVAC fan to circulate the wood heat... which is clearly more drafty than the heat pump. I feel like my opinions on the heat pump were probably overly dramatic.
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skp

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Re: furnace vs heat pump decision
« Reply #2 on: April 22, 2017, 03:06:31 PM »
We have a heat pump. I live in rural NE Ohio and I've had a heat pump for 35 years . Honestly I didn't have a choice- 2here I live gas is not available. I could have gotten propane. But, we chose not to. The pros I see are that I feel my bill is economical I have a 2100 square foot fairly well insulated home and my budget electric bill is $150. That includes heating, air conditioning, everything. It's my only utility bill. I have coworkers who pay $1000 to fill up their propane tanks. My mother has a house 1/2 my size with a gas furnace and her gas + electric utility bills are close to mine. I also think heat pumps are much cleaner than gas. I only have to dust my house every month. I also like that it's a steady heat vs the erratic heat of my mothers gas furnace
You do need to replace them frequently. We are on our third heat pump. I don't think all heat pumps are created equally. The first one we had was a cheaper pump. I was always cold for some reason even when the thermometer said I shouldn't be. This time we bought a more efficient more expensive multiple fan level unit (approx. $5000) and I am much more pleased with it. Heat pumps are getting more efficient everyday. The technology is improving. We were thinking about getting geothermal and I did some research that said that in a few years the efficiency of heat pumps will be on par with geothermal. Geothermal is WAY expensive.
I do know that heat pumps are more efficient when the Temp is above 35 degrees. I've heard that the ideal solution is to have a heat pump with a gas furnace back up. But that would only be necessary if you frequently have temps below that. Otherwise, I think just a heat pump would be best. I am no expert, but I can tell you that I am happy with my heat pump.

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Re: furnace vs heat pump decision
« Reply #3 on: April 22, 2017, 03:45:35 PM »
This seems like an easy decision. You're already installing everything else so, like you said, it's simply a question of adding the heat pump in place of the standard AC unit.

Now, the decision could get complicated if you decide to replace the existing gas furnace. You can likely just have a heat exchanger installed on top with a new thermostat to kick on the gas furnace when needed. The other option is a new dedicated air handler (to replace existing furnace) with gas based backup heat. With the heat pump, your furnace will usually not kick on very often unless it's below freezing so you'll get very little money savings from a new air handler.


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Well Respected Man

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Re: furnace vs heat pump decision
« Reply #4 on: April 22, 2017, 03:49:25 PM »
Since you're getting the AC anyway, why not install the heating portion and have the gas as the "emergency" heat? "Emergency" apparently means that the heat from outside is not warming up the inside fast enough, so it kicks in. If you use electric heat as the "emergency" heat, you will pay more if/when the outside temperature goes below 40* F.

But, since your heating bill is so low, the main savings is getting a new heating system for $400. That's less than $30/year over the life of the system -- not bad.


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Re: furnace vs heat pump decision
« Reply #5 on: April 22, 2017, 05:27:59 PM »
This is from one eco nerd to another, so not all suggestions will be within the range of normal.

1. Have you considered adding a few solar panels for warm water next to, or preferrably underneath, the PV panels? This will help heat your water, and could also heat your house if you have radiators. Solar panels for water underneath the PV can increase their efficiency, since it helps keeping them cool. A larger water tank will let you store energy for a long time, so you are not so depend on warm weather. But there are people in Norway who report working solar panels during winter time, so you should be ok in a temperate climate.
2. Again: if you use water to transport the heat around your house, there are bio based options for heat such as wood fire places with water mantles, or chip/pellet furnaces.
3. Air is less efficient to heat than water. Air to water heat pumps will usually be better than air to air. But heat pumps are better than baseboards. So if you are stuck with heating air: go for the heat pump. Alternatively, if you like burning wood, masonry heaters are great.

The down side with heat pumps is that a lot of people take out the potential savings in increased comfort. They will use it as AC in the summer time, and will keep a steady heat all around the clock instead of turning the heat on and off. A large study in Norway shows that the average citizen barely saves any energy on installing heat pumps, compared to when they were heating with baseboards. But parts of energy loss is because heat pumps have to be designed to the local climate, and a lot of people here have bougth cheap pumps that can't handle temperatures below -20 C.
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Bracken_Joy

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Re: furnace vs heat pump decision
« Reply #6 on: April 22, 2017, 05:39:47 PM »
Since you're getting the AC anyway, why not install the heating portion and have the gas as the "emergency" heat? "Emergency" apparently means that the heat from outside is not warming up the inside fast enough, so it kicks in. If you use electric heat as the "emergency" heat, you will pay more if/when the outside temperature goes below 40* F.

But, since your heating bill is so low, the main savings is getting a new heating system for $400. That's less than $30/year over the life of the system -- not bad.

This is the situation we have- a heat pump with a gas furnace backup. Our ecobee thermostat lets us customize all sorts of parameters- if the heat is changing more than 4 degrees F, then it kicks to the furnace. Or if it's hasn't reached temp within x minutes (I think we're set at 20 right now, but over the winter we set it more like 8 minutes), then it kicks over to the furnace. I feel like we get the best of both worlds this way. Including Old Dog Bone Warming.

If you already have the gas furnace and are adding the heat pump, maybe consider going the dual fuel route. Just be aware very few thermostats are compatible with this now, for some stupid reason. The ecobee is one =) Honeywell said theirs was, but only a certain generation is it turns out (even though it's advertised on all of them) and we couldn't track that one down, in spite of calling their customer service, etc.
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Just Joe

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Re: furnace vs heat pump decision
« Reply #7 on: April 22, 2017, 05:43:37 PM »
https://trane.com/residential/en/resources/about-geothermal/trane-earthwise-hybrid-system.html

So far so good. Is about 3-4 years old now. No troubles.

If you go heat pump avoid the cheap ones. Our house has had several prior to our ownership. They started out builder bottom rung and upgraded each time.

We installed the Trane.
« Last Edit: April 22, 2017, 05:50:23 PM by Tasty Pinecones »

Highbeam

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Re: furnace vs heat pump decision
« Reply #8 on: April 22, 2017, 05:45:39 PM »
Not a hard decision in my opinion. Pay the extra 400$ and be able to heat with either the furnace or the heat pump. Couple of reasons, resale value is better, gas furnace might break so you will have a backup, gas prices may rise, your ability to sell back surplus power may go away, carbon emissions.

Modern heat pumps are much better about high efficiency even when outdoor temps are low.

You're going to want a fancy thermostat for all of this.

Myself, I would replace the entire interior mess with a new gas furnace, air handler, evaporator, all in one unit. Surprised your hvac guy thinks he can just shove in the ac coil.

Bracken_Joy

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Re: furnace vs heat pump decision
« Reply #9 on: April 22, 2017, 05:47:03 PM »
Not a hard decision in my opinion. Pay the extra 400$ and be able to heat with either the furnace or the heat pump. Couple of reasons, resale value is better, gas furnace might break so you will have a backup, gas prices may rise, your ability to sell back surplus power may go away, carbon emissions.

Modern heat pumps are much better about high efficiency even when outdoor temps are low.

You're going to want a fancy thermostat for all of this.

Myself, I would replace the entire interior mess with a new gas furnace, air handler, evaporator, all in one unit. Surprised your hvac guy thinks he can just shove in the ac coil.

Get the fancy thermostat now though, while all the earthday sales are going on! And check your energy council too- we got a $50 check back from Oregon for the ecobee =)
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TomTX

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Re: furnace vs heat pump decision
« Reply #10 on: April 22, 2017, 06:33:24 PM »
I would also suggest running the numbers for replacing your water heater as well - I know we pay around $250/year just to be hooked up to the gas, even if we used zero.
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sol

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Re: furnace vs heat pump decision
« Reply #11 on: April 22, 2017, 06:57:34 PM »
I would also suggest running the numbers for replacing your water heater as well - I know we pay around $250/year just to be hooked up to the gas, even if we used zero.

Electric water heaters are apparently a terrible idea. We pay about $140/year for the natural gas for our hot water, plus $10/mo in connection fee, for a total cost of $250/year to have gas hot water. A 40 gallon electric hot water heater is estimated to use 4600 kWh per year, which would cost us $341. Electricity is just a really inefficient way to heat hot water, even in a place like this where power is very inexpensive. It's not cost effective to replace our gas hot water with electric even if it meant we could stop paying the natural gas connection fee.

Not a hard decision in my opinion. Pay the extra 400$ and be able to heat with either the furnace or the heat pump.

Now the question becomes whether we should install the heat pump with our existing single-speed blower gas furnace, or replace the furnace with a new gas furnace (which could be smaller and use a variable speed fan) or replace the furnace with an air handler with supplemental resistance heat strips. Air handlers and gas furnaces look like they cost about the same.

Quote
Myself, I would replace the entire interior mess with a new gas furnace, air handler, evaporator, all in one unit. Surprised your hvac guy thinks he can just shove in the ac coil.

Our (downflow) furnace is built on a pedestal, so there's easy room for the evap coil underneath it. The furnace blower would apparently be the air handler, with the gas burner turned off during most of the year.

« Last Edit: April 22, 2017, 10:19:42 PM by sol »

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Re: furnace vs heat pump decision
« Reply #12 on: April 22, 2017, 07:34:18 PM »
Sol I've had an air source heat pump for over 20 years. On the second system now. Only time it doesn't do well is in rainy, cold weather. The coils freeze up and it takes extra energy for it to defrost during reverse cycle. If I were to have a do over I'd go geothermal.
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wienerdog

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Re: furnace vs heat pump decision
« Reply #13 on: April 23, 2017, 06:26:44 AM »
I would spend the extra money on the heat pump. Depending on your low temps it might be able to cover 100% of your heating season (dependent of course on house losses). Once the outside temp gets below 35F - 40F it is probably cheaper to heat with gas but prices always change so that crossover point might change in the future. I spent the extra money on a heat pump when I replaced my gas and AC in my old house. Go for the a decent variable speed blower and you will have better humidity control which will let you keep it warmer but feel just as comfortable during the cooling season. Or at least a 2 speed fan.

One major factor in life of your AC / Heat pump unit is the installation. Most installers won't use a nitrogen purge while brazing the refrigeration piping. Ask your installer if he will. If he doesn't know what you are talking about or says no run as fast as you can from them. Life isn't really dependent on the equipment selection it is on the install.

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Papa bear

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Re: furnace vs heat pump decision
« Reply #14 on: April 23, 2017, 07:01:12 AM »
We have a heat pump. I live in rural NE Ohio and I've had a heat pump for 35 years . Honestly I didn't have a choice- 2here I live gas is not available. I could have gotten propane. But, we chose not to. The pros I see are that I feel my bill is economical I have a 2100 square foot fairly well insulated home and my budget electric bill is $150. That includes heating, air conditioning, everything. It's my only utility bill. I have coworkers who pay $1000 to fill up their propane tanks. My mother has a house 1/2 my size with a gas furnace and her gas + electric utility bills are close to mine. I also think heat pumps are much cleaner than gas. I only have to dust my house every month. I also like that it's a steady heat vs the erratic heat of my mothers gas furnace
You do need to replace them frequently. We are on our third heat pump. I don't think all heat pumps are created equally. The first one we had was a cheaper pump. I was always cold for some reason even when the thermometer said I shouldn't be. This time we bought a more efficient more expensive multiple fan level unit (approx. $5000) and I am much more pleased with it. Heat pumps are getting more efficient everyday. The technology is improving. We were thinking about getting geothermal and I did some research that said that in a few years the efficiency of heat pumps will be on par with geothermal. Geothermal is WAY expensive.
I do know that heat pumps are more efficient when the Temp is above 35 degrees. I've heard that the ideal solution is to have a heat pump with a gas furnace back up. But that would only be necessary if you frequently have temps below that. Otherwise, I think just a heat pump would be best. I am no expert, but I can tell you that I am happy with my heat pump.


Do you have another source of heat for your home? Is it built for solar efficiency or have a wood burning stove? I ask because I have absolutely 100% the opposite experience of you.

We are in a an original all electric neighborhood in suburban central Ohio built in the late 70's and early 80's. I can attest that these homes were built very efficiently during the energy crisis.

Natural gas wasn't available in parts of my neighborhood until a few years ago. And being the neighborhood handyman, do everything guy, I have helped or referred on work to replace heat pumps with gas furnaces on more than a dozen homes. It was not unusual to have electric bills over 700!!!/ month with some of these homes, most of which are under 2000sqft. Newer heat pumps and systems usually ran around 300-400/ month for electric bills during the winters. And this is an area with CHEAP electric in the range of $.06-$.08/kWh.

After the change to gas furnace, these same neighbors have total utility bills cut down 200-500/month. The new gas system pay back period for some of these homes was under 1 year. Insane.

So a bill totaling 150/month sounds implausible without some other input.


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DavidAnnArbor

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Re: furnace vs heat pump decision
« Reply #15 on: April 23, 2017, 01:51:24 PM »
New natural gas furnaces are like 95% efficient, but they cost thousands of dollars.

theglidd

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Re: furnace vs heat pump decision
« Reply #16 on: April 23, 2017, 03:52:51 PM »
I'd go with the heat pump based on your current rates/location.

New heat pumps have a COP around 3. (300%)

Your current rate structure is around $8.80/mmbtu vs $20.00/mmbtu. So the efficiency will make up the unit cost difference.

Plus you can always offset the electric with renewable.

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Re: furnace vs heat pump decision
« Reply #17 on: April 23, 2017, 04:25:36 PM »
I think you can be better off with a heat pump, especially if your furnace is getting close to the end of it's life. Would it impact your financial decision regarding your solar panel install?

My stepdad is a builder in PNW and, being a bit of a traditionalist, he was always dead-set against whole house air-source heat pumps... until he installed a Japanese made one at a remote property with no gas service. Worked like a charm and ran at low cost. It was probably 10 years back now, but I believe it was a variable speed Mitsubishi model.

Just be careful to get the right one. There are a lot of pricey parts that can go wrong and some brands are notoriously unreliable. Also a true variable speed motor is much better performing and quieter than the typical and cheaper 2 stage motor units out there.

I also know of a few projects he did where traditional heat pumps were installed together with furnace backups. They were mostly Lennox and Bryant systems and they seemed to perform quite well. Going this route is not economical in my opinion though. This was back when gas prices were projected to fly off the charts and people thought electric heat would do well to lower heating costs.

Good luck with your decision.
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sol

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Re: furnace vs heat pump decision
« Reply #18 on: April 23, 2017, 05:01:05 PM »
Would it impact your financial decision regarding your solar panel install?

Not really. Our solar panels mostly make money because the state pays us 54 cents/kWh for our production on the roof, regardless of how much of that we use in our house or how much we send to the grid. That deal is capped at $5k/year and expires in 2020, but that will be enough to offset the out-of-pocket costs for our solar system. Our local power consumption has basically no effect, since every kWh we use we either pay for or don't get paid for. Costs us the same to use more power either way.

Quote
I also know of a few projects he did where traditional heat pumps were installed together with furnace backups. They were mostly Lennox and Bryant systems and they seemed to perform quite well. Going this route is not economical in my opinion though.

Why is that not economical? Right now I'm leaning towards getting the heat pump and a new gas furnace, because a new gas furnace is basically the same cost as a new air handler, and you only need one or the other. If I'm going to get the heat pump, and I think I am, then my options are:

1. Go full electric, heat pump plus air handler plus electric strip heaters for supplementary heat in the coldest parts of winter.

2. Go dual-fuel, heat pump plus a new gas furnace with a variable speed fan.

3. Go dual fuel, heat pump plus keep our existing 20 year old gas furnace with the single speed fan.

In the depths of winter when the heat pump may not be sufficient by itself, I think natural gas heating is cheaper than straight resistance heating, based on the math I showed at the top of the thread. Heat pump appears to have the lowest operating costs, then natural gas, then the strip heaters. Unless the install cost on the new gas furnace is significantly higher than the install cost on the air handler with strip heaters, I'd rather leave electric strip heaters out of the system.

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Re: furnace vs heat pump decision
« Reply #19 on: April 23, 2017, 05:23:35 PM »
I would also suggest running the numbers for replacing your water heater as well - I know we pay around $250/year just to be hooked up to the gas, even if we used zero.

Electric water heaters are apparently a terrible idea. We pay about $140/year for the natural gas for our hot water, plus $10/mo in connection fee, for a total cost of $250/year to have gas hot water. A 40 gallon electric hot water heater is estimated to use 4600 kWh per year, which would cost us $341. Electricity is just a really inefficient way to heat hot water, even in a place like this where power is very inexpensive. It's not cost effective to replace our gas hot water with electric even if it meant we could stop paying the natural gas connection fee.

We have a 40 gallon electric water heater. Our total electric usage in the past 12 months was 4500 kWh, so I question whatever source told you that this one appliance would use 4600 kWh all on its own. All the other appliances in our house except the furnace are electric, and we use the dryer rather frequently. If I had a chance to pay $400 to shut the gas off entirely and run completely on hydro power, I'd probably take it.
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theglidd

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Re: furnace vs heat pump decision
« Reply #20 on: April 23, 2017, 05:47:02 PM »
"I think natural gas heating is cheaper than straight resistance heating"

It unquestionably is. Your unit cost for natural gas is $8.80/mmbtu while the unit cost for electric is around $20.00/mmbtu.

You pay more than twice as much for electric than natural gas. (ignoring efficiency factors, 80% vs 100%)

The only reason a heat pump makes sense is because you live in a mild climate and they have great efficiency.

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Re: furnace vs heat pump decision
« Reply #21 on: April 23, 2017, 05:54:38 PM »
I also know of a few projects he did where traditional heat pumps were installed together with furnace backups. They were mostly Lennox and Bryant systems and they seemed to perform quite well. Going this route is not economical in my opinion though.

Why is that not economical? Right now I'm leaning towards getting the heat pump and a new gas furnace, because a new gas furnace is basically the same cost as a new air handler, and you only need one or the other. If I'm going to get the heat pump, and I think I am, then my options are:

1. Go full electric, heat pump plus air handler plus electric strip heaters for supplementary heat in the coldest parts of winter.

2. Go dual-fuel, heat pump plus a new gas furnace with a variable speed fan.

3. Go dual fuel, heat pump plus keep our existing 20 year old gas furnace with the single speed fan.

In the depths of winter when the heat pump may not be sufficient by itself, I think natural gas heating is cheaper than straight resistance heating, based on the math I showed at the top of the thread. Heat pump appears to have the lowest operating costs, then natural gas, then the strip heaters. Unless the install cost on the new gas furnace is significantly higher than the install cost on the air handler with strip heaters, I'd rather leave electric strip heaters out of the system.

Most of the homeowners who went the heat pump + furnace did so instead of AC + furnace. At the time a good heat pump costed much more than an AC. The +/- $1000 extra cost for the heat pump would take a long time to pay for itself if they're still buying a nice 92+ efficient furnace.

Some of the better foreign made heat pumps should run well into the -25C/-10F range. Should be adequate for PNW without supplement strip heat?

I'm not sure what the cost implications of two installs would be, but Option 3 might be the safe bet. If you run it a few winters and the heat pump keeps up no problem you can always swap out the old box for a shiny new air handler and not worry about the cost of putting in strip heat. That opens up the possibility of full electric down the road at a lower cost and is potentially the "greenest".

You could then be doubly smug: green system and the confidence it works in your climate. :)
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Re: furnace vs heat pump decision
« Reply #22 on: April 23, 2017, 06:17:40 PM »
We've had both (heat pump since 2011) and I prefer the heat pump for the reasons you mentioned. It keeps up pretty well except on the rare below zero days/ nights we get in NC but that's maybe 2-3 times per year.

sol

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Re: furnace vs heat pump decision
« Reply #23 on: April 23, 2017, 07:58:35 PM »
I've been reading the manual on a specific proposed heat pump in one of the bids I've received. The cooling efficiency is going to be whatever it is going to be, and I expect to pay more to run an air conditioner than not run an air conditioner. Fine.

But on the heating side of the equation, I was trying to figure out the temperature at which supplemental heating (strip heaters or gas furnace) would be more cost effective than continuing to run the heat pump at reduced efficiency. The attached table kind of blew my mind.

Why? I was expecting the COP of ~3.0 (=300% efficient) for moderate heating loads. That jibes well with my basic understanding of thermodynamics. I expected the heating efficiency rating to drop as temperatures declined. But those COP values don't drop below 3.0 until you hit ~35 degrees F, and they don't drop below 2.0 until 5 degrees F, and they don't drop below 1.0 until somewhere below -5 degrees F.

Based on the math earlier in this thread, I figured that a heat pump operating at 200% efficiency would cost me about the same to run as an 80% AFUE gas furnace. And of course anything above a 100% is still more efficient than electrical resistance heating. This means natural gas is only the most cost effective way to heat between about +10 and -10 degrees F. Below about -10 degrees F, resistance heaters are cheaper. But we never get that cold.

Is the supplemental heat just to help your house warm up faster? Because it sure doesn't look cost effective, at least not until you reach single digit temps.




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Re: furnace vs heat pump decision
« Reply #24 on: April 23, 2017, 08:31:25 PM »

Is the supplemental heat just to help your house warm up faster? Because it sure doesn't look cost effective, at least not until you reach single digit temps.

Mostly but it also provides heat when the heat pump needs to defrost its coils. Basically, depending on outside temps and humidity, the heat pump reverses into AC mode and pulls some heat from the house to melt any frost/ice that has built up on the outdoor unit. The supplemental heat prevents cold air blowing during this time. Also, provides a backup heating source if outdoor compressor fails (have had this happen with my unit but was an easy fix).


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Re: furnace vs heat pump decision
« Reply #25 on: April 24, 2017, 08:17:52 AM »
I've been reading the manual on a specific proposed heat pump in one of the bids I've received. The cooling efficiency is going to be whatever it is going to be, and I expect to pay more to run an air conditioner than not run an air conditioner. Fine.

But on the heating side of the equation, I was trying to figure out the temperature at which supplemental heating (strip heaters or gas furnace) would be more cost effective than continuing to run the heat pump at reduced efficiency. The attached table kind of blew my mind.

Why? I was expecting the COP of ~3.0 (=300% efficient) for moderate heating loads. That jibes well with my basic understanding of thermodynamics. I expected the heating efficiency rating to drop as temperatures declined. But those COP values don't drop below 3.0 until you hit ~35 degrees F, and they don't drop below 2.0 until 5 degrees F, and they don't drop below 1.0 until somewhere below -5 degrees F.

Based on the math earlier in this thread, I figured that a heat pump operating at 200% efficiency would cost me about the same to run as an 80% AFUE gas furnace. And of course anything above a 100% is still more efficient than electrical resistance heating. This means natural gas is only the most cost effective way to heat between about +10 and -10 degrees F. Below about -10 degrees F, resistance heaters are cheaper. But we never get that cold.

Is the supplemental heat just to help your house warm up faster? Because it sure doesn't look cost effective, at least not until you reach single digit temps.

Thank you for this! Husband and I tried to look for exactly this when we were setting up our thermostat- there's a setting for minimum running outdoor temp for the heat pump (it defaults to 36F, which I think we ended up keeping). We still need to try to figure out what it would be for our heat pump (because that would vary, right?), given that it is from 1995 haha.
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Re: furnace vs heat pump decision
« Reply #26 on: April 24, 2017, 04:16:17 PM »
[/quote]
We have a heat pump. I live in rural NE Ohio and I've had a heat pump for 35 years . Honestly I didn't have a choice- 2here I live gas is not available. I could have gotten propane. But, we chose not to. The pros I see are that I feel my bill is economical I have a 2100 square foot fairly well insulated home and my budget electric bill is $150. That includes heating, air conditioning, everything. It's my only utility bill. I have coworkers who pay $1000 to fill up their propane tanks. My mother has a house 1/2 my size with a gas furnace and her gas + electric utility bills are close to mine. I also think heat pumps are much cleaner than gas. I only have to dust my house every month. I also like that it's a steady heat vs the erratic heat of my mothers gas furnace
You do need to replace them frequently. We are on our third heat pump. I don't think all heat pumps are created equally. The first one we had was a cheaper pump. I was always cold for some reason even when the thermometer said I shouldn't be. This time we bought a more efficient more expensive multiple fan level unit (approx. $5000) and I am much more pleased with it. Heat pumps are getting more efficient everyday. The technology is improving. We were thinking about getting geothermal and I did some research that said that in a few years the efficiency of heat pumps will be on par with geothermal. Geothermal is WAY expensive.
I do know that heat pumps are more efficient when the Temp is above 35 degrees. I've heard that the ideal solution is to have a heat pump with a gas furnace back up. But that would only be necessary if you frequently have temps below that. Otherwise, I think just a heat pump would be best. I am no expert, but I can tell you that I am happy with my heat pump.


Do you have another source of heat for your home? Is it built for solar efficiency or have a wood burning stove? I ask because I have absolutely 100% the opposite experience of you.

We are in a an original all electric neighborhood in suburban central Ohio built in the late 70's and early 80's. I can attest that these homes were built very efficiently during the energy crisis.

Natural gas wasn't available in parts of my neighborhood until a few years ago. And being the neighborhood handyman, do everything guy, I have helped or referred on work to replace heat pumps with gas furnaces on more than a dozen homes. It was not unusual to have electric bills over 700!!!/ month with some of these homes, most of which are under 2000sqft. Newer heat pumps and systems usually ran around 300-400/ month for electric bills during the winters. And this is an area with CHEAP electric in the range of $.06-$.08/kWh.

After the change to gas furnace, these same neighbors have total utility bills cut down 200-500/month. The new gas system pay back period for some of these homes was under 1 year. Insane.

So a bill totaling 150/month sounds implausible without some other input.


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My house is the same age as yours. We do have a wood burner in our family room that we run sometimes but not 24/7 in the winter. It heats one room of the house. The only other difference I can see is that I bet I use my air conditioning a lot less than you. It's a lot less hot and humid in NE ohio vs central ohio. I am a freeze baby we keep our heat on 68 in the winter and I wear a sweater in winter but don't mine a 76 degree house in the summer. $700 sounds outrageous. Are these heat pumps old or inefficient? My newer heat pump (multiple fans) was more expensive to purchase but costs less in the long run because my bills are lower and I am much more comfortable with it.

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Re: furnace vs heat pump decision
« Reply #27 on: April 24, 2017, 05:07:45 PM »
We have a heat pump. I live in rural NE Ohio and I've had a heat pump for 35 years . Honestly I didn't have a choice- 2here I live gas is not available. I could have gotten propane. But, we chose not to. The pros I see are that I feel my bill is economical I have a 2100 square foot fairly well insulated home and my budget electric bill is $150. That includes heating, air conditioning, everything. It's my only utility bill. I have coworkers who pay $1000 to fill up their propane tanks. My mother has a house 1/2 my size with a gas furnace and her gas + electric utility bills are close to mine. I also think heat pumps are much cleaner than gas. I only have to dust my house every month. I also like that it's a steady heat vs the erratic heat of my mothers gas furnace
You do need to replace them frequently. We are on our third heat pump. I don't think all heat pumps are created equally. The first one we had was a cheaper pump. I was always cold for some reason even when the thermometer said I shouldn't be. This time we bought a more efficient more expensive multiple fan level unit (approx. $5000) and I am much more pleased with it. Heat pumps are getting more efficient everyday. The technology is improving. We were thinking about getting geothermal and I did some research that said that in a few years the efficiency of heat pumps will be on par with geothermal. Geothermal is WAY expensive.
I do know that heat pumps are more efficient when the Temp is above 35 degrees. I've heard that the ideal solution is to have a heat pump with a gas furnace back up. But that would only be necessary if you frequently have temps below that. Otherwise, I think just a heat pump would be best. I am no expert, but I can tell you that I am happy with my heat pump.


Do you have another source of heat for your home? Is it built for solar efficiency or have a wood burning stove? I ask because I have absolutely 100% the opposite experience of you.

We are in a an original all electric neighborhood in suburban central Ohio built in the late 70's and early 80's. I can attest that these homes were built very efficiently during the energy crisis.

Natural gas wasn't available in parts of my neighborhood until a few years ago. And being the neighborhood handyman, do everything guy, I have helped or referred on work to replace heat pumps with gas furnaces on more than a dozen homes. It was not unusual to have electric bills over 700!!!/ month with some of these homes, most of which are under 2000sqft. Newer heat pumps and systems usually ran around 300-400/ month for electric bills during the winters. And this is an area with CHEAP electric in the range of $.06-$.08/kWh.

After the change to gas furnace, these same neighbors have total utility bills cut down 200-500/month. The new gas system pay back period for some of these homes was under 1 year. Insane.

So a bill totaling 150/month sounds implausible without some other input.


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My house is the same age as yours. We do have a wood burner in our family room that we run sometimes but not 24/7 in the winter. It heats one room of the house. The only other difference I can see is that I bet I use my air conditioning a lot less than you. It's a lot less hot and humid in NE ohio vs central ohio. I am a freeze baby we keep our heat on 68 in the winter and I wear a sweater in winter but don't mine a 76 degree house in the summer. $700 sounds outrageous. Are these heat pumps old or inefficient? My newer heat pump (multiple fans) was more expensive to purchase but costs less in the long run because my bills are lower and I am much more comfortable with it.
[/quote]

I was just comparing winter utility bills. I have a newer unit (8-10 years old) and kept the house on the cool side (mid 60's) Had bills in mid 300's. The 700+ bills were older or original heat pump units - not sure of internal house temp as these were neighbors' homes. New natural gas furnace, 96% efficient, cost me 800+ labor and gas bills are under 70 during the winter and with an infant, we kept the place toasty.

The neighborhood jokes about heat pump heat and how "cold" it is. We call it the heat pump wind chill factor.

My electric bills are still in the 80-140 range, mostly attributed to an electric hot water tank. I'm switching that to heat pump H2O due to rebates and sale prices on the unit.

My home gets little to no solar heat gain. In fact there are only 3 smaller south facing windows on the house. We do have a wood burning fireplace insert, but my wife hates the smoke, so it was rarely used.

I'm not knocking heat pumps - I have them elsewhere (warmer climates) and think they can be very efficient.


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theglidd

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Re: furnace vs heat pump decision
« Reply #28 on: April 24, 2017, 05:27:40 PM »
"Based on the math earlier in this thread, I figured that a heat pump operating at 200% efficiency would cost me about the same to run as an 80% AFUE gas furnace. And of course anything above a 100% is still more efficient than electrical resistance heating. This means natural gas is only the most cost effective way to heat between about +10 and -10 degrees F. Below about -10 degrees F, resistance heaters are cheaper. But we never get that cold. "

Sol using electric resistance heat will never be cost effective for you, no matter what the temperature, unless your gas rate doubles. Which likely won't happen anytime soon based on US natural gas reserves.

When doing energy analysis it's important to compare current energy rates and efficiency. Otherwise you are only seeing one part of the picture.

Going the heat pump route with gas backup is your most efficient and cost effective option.

sol

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Re: furnace vs heat pump decision
« Reply #29 on: April 24, 2017, 06:56:34 PM »
Going the heat pump route with gas backup is your most efficient and cost effective option.

I agree, at least on the operating costs side. I'm still trying to figure out what the cost differential is on the installation side.

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Re: furnace vs heat pump decision
« Reply #30 on: April 25, 2017, 07:21:21 AM »
so I LOVE my heat pump and it is saving me over $1000/year but you need to do your own math. I'm on propane at about $2.99/Therm and I live in a climate where I was going through more like 700 therm a year. Heat pump easily helped out. I also like how quiet it is.

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Re: furnace vs heat pump decision
« Reply #31 on: April 25, 2017, 08:17:38 AM »
I agree with others that natural gas is currently and likely to be for the foreseeable future (at least a couple of decades) much cheaper than electric, though of course gas is not always available. We lived in CT for over a decade with no gas service, and after paying for electric baseboard heat for a few years put in a pellet stove. We've now moved to NJ, and natural gas is substantially cheaper even than the pellet stove was, as well as a lot less work.

The main downside I would see for a heat pump is that the air they put out is cooler, and higher volume, so can feel drafty. Part of how they are so efficient is by barely heating the air a bit above the temperature you set, and moving lots of it. That bothers some people a lot, not others. My suggestion since it is so cheap is get the heat pump add-on, keep the existing furnace, and see if you are comfy without running the furnace for the next few years, and if the bills are lower. If you are successful on both those measures, then you don't need to replace it.

DavidAnnArbor

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Re: furnace vs heat pump decision
« Reply #32 on: April 25, 2017, 04:58:20 PM »
One disadvantage of natural gas furnaces is that there is a slight danger of Carbon Monoxide poisoning. Also, there are probably other combustion products as well besides carbon monoxide. It may just be a fear that I am overstating, but something to consider.

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Re: furnace vs heat pump decision
« Reply #33 on: April 26, 2017, 09:22:23 AM »
In the depths of winter when the heat pump may not be sufficient by itself, I think natural gas heating is cheaper than straight resistance heating, based on the math I showed at the top of the thread. Heat pump appears to have the lowest operating costs, then natural gas, then the strip heaters. Unless the install cost on the new gas furnace is significantly higher than the install cost on the air handler with strip heaters, I'd rather leave electric strip heaters out of the system.

You don't get cold enough to really require much resistive heating out there unless you're way up in the mountains (and since you have natural gas, that's not likely).

I'm out in Idaho now, and we had a brutally cold winter - -11F lows, quite a few days below 0, etc. We've got a new manufactured home with a heat pump, and the worst I paid for power (admittedly cheaper than your power) was about $260 for the super-cold month. That's purely electric everything - we don't have any gas stuffs anywhere in the house.

The modern air source heat pumps work down pretty cold, as you've learned.

One thing I will say - spend the money on a thermostat that understands heat pumps. The one that came with our system was rock dumb - I was cooking the house to get some volatiles out after it was built. It was 90 degrees out. I asked for a big temperature rise and it immediately turned on the backup coils. There's no reason to do that.

Our Nest seems was pretty good about starting the heat pump early - it'd start it at 4AM some mornings to get the house up to temperature by 8, but it was able to do it mostly without touching the backup coils unless it was really cold (or the defrost cycle kicked in - that seems to be timer based, and given how dry it is out here, was generally not needed or appreciated).

The Nest will also run a dual fuel system (heat pump plus gas backup), if you go that route, and will try to be smart about it.
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sol

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Re: furnace vs heat pump decision
« Reply #34 on: April 26, 2017, 10:00:51 AM »
We're already anticipating a Nest 3. It's cheaper right now ($125), due to earth day sales and local energy company rebates. The EcoBee3 is also down to $99, and I think smarthome devices in general will only get cheaper from here on out.

My preferred furnace guy is a local installer, not one of the big name brand pushers. His bid was about $2k less than everyone else, for equivalent hardware, but he only answers his phone about one day a week so the whole process is moving slowly. I want to shout at him "please let me pay you thousands of dollars!" but he just doesn't seem that interested in finding new work.

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Re: furnace vs heat pump decision
« Reply #35 on: April 26, 2017, 12:49:00 PM »
I want to shout at him "please let me pay you thousands of dollars!" but he just doesn't seem that interested in finding new work.

Based on that, I presume you live somewhere in the Seattle metro area or surrounding towns? That's pretty much every contractor out there. Way too busy with work to bother answering their phone.
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Kroaler

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Re: furnace vs heat pump decision
« Reply #36 on: April 27, 2017, 12:42:12 PM »
I'm surprised nobody has mentioned heat pump water heaters. They are cheap relative to the technology they use. (My opinion)

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Re: furnace vs heat pump decision
« Reply #37 on: April 27, 2017, 12:52:36 PM »
so i've contemplated this as well. i like your analysis i may take it on myself for our home.

A few notes

1. around here most of my gas charge is related just to having it connected. over 30 dollars a month just for the privledge of connection. SO if you're going to go electric on your house heating why not go electric on your water and cut the gas line?
2. I'm sure its been brought up but heat pumps lose efficiency relative to outside temp. not sure how this affects your region but ours we get some really cold winters ever now and then.
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Re: furnace vs heat pump decision
« Reply #38 on: April 27, 2017, 01:13:38 PM »
I think you've got a good handle on what affects the economics etc. In my house, we have a hybrid system where I've disabled the Heat Pump because gas is too cheap. We have a $4 connection fee and pay $0.67 per therm.

The reason I turned the HP and AC off at the breaker is because there is a sump heater pulling 68W all the time to keep refrigerant from pooling in the compressor. This is a big waste of energy ($70/yr at $0.12 /kWh), and I heat my house for 1/3rd of the winter for that money. So I keep the breaker off, and remember to turn it on 6 hours in advance of a 100 degree day when I feel like I'll need the cooling.

Sol, you should see if the sump heater wattage is spec'd on your quote. They can often be much smaller, but heat pumps generally get big ones since they operate in cold weather...

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Re: furnace vs heat pump decision
« Reply #39 on: April 27, 2017, 06:30:50 PM »
I'm surprised nobody has mentioned heat pump water heaters. They are cheap relative to the technology they use. (My opinion)

I've heard of them but don't know much about them. Do you have any idea how long it takes to rebound a cooled tank of water? My experience (long ago) with heat pumps and my experience with resistance heated water heaters (also slow) makes me think it might take a while.

This might be fine for a household with one or two inhabitants. I'm skeptical for a large family. But I'm also clueless. I'm just as likely to be wrong.
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Re: furnace vs heat pump decision
« Reply #40 on: April 27, 2017, 07:52:52 PM »
We put AC into our fixer upper and decided to start fresh w new dual fuel heat pump/efficient furnace. No regrets. The furnace heat is so much warmer but for efficiency's sake I only run under 40deg. Also, don't get a bigger unit than you need (measured in tons but I forgetting​ our numbers - just be sure to factor in insulation etc). Oversizing the unit would be a waste. Enjoy!

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Re: furnace vs heat pump decision
« Reply #41 on: April 27, 2017, 09:08:06 PM »
Would it impact your financial decision regarding your solar panel install?

Not really. Our solar panels mostly make money because the state pays us 54 cents/kWh for our production on the roof, regardless of how much of that we use in our house or how much we send to the grid. That deal is capped at $5k/year and expires in 2020, but that will be enough to offset the out-of-pocket costs for our solar system. Our local power consumption has basically no effect, since every kWh we use we either pay for or don't get paid for. Costs us the same to use more power either way.

Quote

Lennox and Bryant systems and they seemed to perform quite well. Going this route is not economical in my opinion though.

Why is that not economical? Right now I'm leaning towards getting the heat pump and a new gas furnace, because a new gas furnace is basically the same cost as a new air handler, and you only need one or the other. If I'm going to get the heat pump, and I think I am, then my options are:

1. Go full electric, heat pump plus air handler plus electric strip heaters for supplementary heat in the coldest parts of winter.

2. Go dual-fuel, heat pump plus a new gas furnace with a variable speed fan.

3. Go dual fuel, heat pump plus keep our existing 20 year old gas furnace with the single speed fan.

In the depths of winter when the heat pump may not be sufficient by itself, I think natural gas heating is cheaper than straight resistance heating, based on the math I showed at the top of the thread. Heat pump appears to have the lowest operating costs, then natural gas, then the strip heaters. Unless the install cost on the new gas furnace is significantly higher than the install cost on the air handler with strip heaters, I'd rather leave electric strip heaters out of the system.

Electric might be the most efficient on paper, but it is a poor way to heat a house. If I could re do our heating system, we would install a heat pump with propane or natural gas as a secondary. We currently have a furnace that can run on propane or electric, and by using propane I've saved $200-300/month.

Frugal friends use a heat pump up until it gets too cold and switch to propane. I do like the feeling of heat that comes from the ducts with gas/propane-it is blowing warmer air than electric.

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Re: furnace vs heat pump decision
« Reply #42 on: April 28, 2017, 05:16:48 AM »

Frugal friends use a heat pump up until it gets too cold and switch to propane. I do like the feeling of heat that comes from the ducts with gas/propane-it is blowing warmer air than electric.

I prefer my ground source heat pump. The heat source stays a constant temperature and I haven't had to use backup heat in 3 years since I customized the controls of the thermostat. Some days it almost runs 24 hours in a day but it just tells me they hit the design proper. :>) When it dies I pan to install a 2 speed unit so it isn't over sized so much on those more mild days.

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Re: furnace vs heat pump decision
« Reply #43 on: April 28, 2017, 06:44:48 AM »

Frugal friends use a heat pump up until it gets too cold and switch to propane. I do like the feeling of heat that comes from the ducts with gas/propane-it is blowing warmer air than electric.

I prefer my ground source heat pump. The heat source stays a constant temperature and I haven't had to use backup heat in 3 years since I customized the controls of the thermostat. Some days it almost runs 24 hours in a day but it just tells me they hit the design proper. :>) When it dies I pan to install a 2 speed unit so it isn't over sized so much on those more mild days.

man i wish i had one of those. my parents house had one. cost of construction is just so high.
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Re: furnace vs heat pump decision
« Reply #44 on: May 08, 2017, 07:41:29 PM »

Frugal friends use a heat pump up until it gets too cold and switch to propane. I do like the feeling of heat that comes from the ducts with gas/propane-it is blowing warmer air than electric.

I prefer my ground source heat pump. The heat source stays a constant temperature and I haven't had to use backup heat in 3 years since I customized the controls of the thermostat. Some days it almost runs 24 hours in a day but it just tells me they hit the design proper. :>) When it dies I pan to install a 2 speed unit so it isn't over sized so much on those more mild days.

Curious on how what temperature range you experience? That would be ideal; I'm just not sure that our climate would allow for that setup- our average temperature is below freezing for 5 months per year, and in particularly cold years there have been entire months where it doesn't get above 0. Made for some brutal days walking to class :).

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Re: furnace vs heat pump decision
« Reply #45 on: May 08, 2017, 09:20:11 PM »
Curious on how what temperature range you experience? That would be ideal; I'm just not sure that our climate would allow for that setup- our average temperature is below freezing for 5 months per year, and in particularly cold years there have been entire months where it doesn't get above 0. Made for some brutal days walking to class :).

That type of climate makes a ground source heat pump ideal - you're pumping heat from a ~50F source instead of trying to pump from sub-zero.

It's unlikely to work unless you have a well sealed house - heat pumps are fine with leaky homes in moderate climates, but they're not amazing with leaky homes in the extreme cold. A natural gas furnace is easier in that case. Possibly not cheaper, but they tend to have more headroom.

If it gets cold enough (or if you tend to lose power in the winter), you might want to go with a dual fuel setup (ground source heat pump, natural gas furnace for backup heat, which is also a lot easier to run off a generator if you wire things up properly).
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sol

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Re: furnace vs heat pump decision
« Reply #46 on: May 08, 2017, 09:23:11 PM »
My heat pump should go in next week.

Does anyone have any thoughts on electronic air cleaners vs media filters? My preliminary research suggests they are roughly the same cost, itemized over a 10 year lifetime, but the EAC offers better filtration with less pressure drop and costs more up front.

EPA claims EACs are roughly equivalent to a MERV 15 filter.
Four inch MERV 13 filters are about $40 per filter change, twice per year, or about $800 over 10 years.
The EAC costs about $700 up front, plus about $10/year in power consumption costs, or about $800 over 10 years.

I also learned that if you have problems with allergies, your furnace filter is the least helpful thing in your home because the particles that cause problems are too large to stay suspended in the air long enough for your HVAC system to capture. EPA says you need to vacuum and dust more often, which I guess means sneezy people are just going to be sneezy.

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Re: furnace vs heat pump decision
« Reply #47 on: May 08, 2017, 10:44:00 PM »
Appologies for not reading the whole thread...

Last week I just ran the IRR numbers to replace an electric furnace with a gas furnace. We currently have supplemental baseboard heat in this building, and I threw in a calculation for radiant ceiling (electric) panels as well.

The space is a 3200sq.ft community hall with a currently broken electric furnace.

COST -- Assume electricity at 11 cents / KW.h and natural gas at $8 per GJ (all in variable costs). The natural gas furnace is 95% efficient, and the electric heat (any type) is 100% efficient on the heating portion.

Based on this pricing, for the same BTU's, natural gas is 5x CHEAPER than electric heat. Of course, natural gas is at a 10 year low in price right now...

For us, the cost of natural gas includes extending a line and buying a fairly expensive new furnace. All in $6500 (it's a commercial type furnace).

This means that they payback for natural gas is between 4 and 5 years, compared to just repairing the existing electric furnace. After that the natural gas is cheaper.
We can also put in a gas hot water tank in future, for more savings, but that was not calculated.

As a bonus, we are looking at keeping the space cool, at 60'F all the time, and using radiant panels to bump up the perceived heat in the space when it is used for just an hour or two. This also has a payback (due to less heating as the furnace is slow), of about 4-5 years. IRR for 10 years is 19%. IRR for 5 years is 4%.

LOCATION / CLIMATE -- Vancouver, BC


So -- does a 5 year (worst case) payback for natural gas make sense to you versus baseboard or electric heat? Do you plan to leave the place sooner and won't get your capital back in a resale? Do you plan to stay 10 years and like a 19% IRR?


Spork

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Re: furnace vs heat pump decision
« Reply #48 on: May 09, 2017, 06:20:35 AM »
My heat pump should go in next week.

Does anyone have any thoughts on electronic air cleaners vs media filters? My preliminary research suggests they are roughly the same cost, itemized over a 10 year lifetime, but the EAC offers better filtration with less pressure drop and costs more up front.

EPA claims EACs are roughly equivalent to a MERV 15 filter.
Four inch MERV 13 filters are about $40 per filter change, twice per year, or about $800 over 10 years.
The EAC costs about $700 up front, plus about $10/year in power consumption costs, or about $800 over 10 years.

I also learned that if you have problems with allergies, your furnace filter is the least helpful thing in your home because the particles that cause problems are too large to stay suspended in the air long enough for your HVAC system to capture. EPA says you need to vacuum and dust more often, which I guess means sneezy people are just going to be sneezy.

Talk to the guys that design your setup. There is going to be a max pressure drop for a given system based on the blower, length of duct work, etc. Normally more filtration means more pressure drop and can toss your system back into being less efficient. In other words: better filtration doesn't necessarily mean better operation of the unit.
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theglidd

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Re: furnace vs heat pump decision
« Reply #49 on: May 09, 2017, 11:36:18 AM »
For residential applications I'd recommend a MERV rating no higher than 4. Any higher provides minimal benefit and just increases cost/decrease efficiency.

The filter is just to protect the fan and coils from fowling. Not for indoor air quality purposes.