heat pump vs wood

[Newbie78]

Well. They work well. And we have become accustomed to a far warmer house than ever before.

If I didn't have to use the NG furnace to keep the basement plumbing from freezing in really cold weather I would be fully wood-heated. The way it is, I'd say I'm over 95% woodheat. My gas bills are tiny. We pay more for the administration fee than the gas. Far more.

 

[ColoradoPine]

This depends on the type of heat pump and the structure. A new, super efficient, air tight house in a moderate climate is going to have pretty low heating load to begin with. Throw in something like the 21 seer Bosch Bova heat pump and you have a very, very low heating cost regardless of rates. If a mini split would work for the house, you can go up to 40+ seer. The efficiency on some of the new equipment is insane, and it works in much colder weather than the old heat pumps did. But that's all a discussion about ongoing cost.

However, my guess is most people here on Hearth.com aren't in the process of building a .3 ACH50 passive house in Tennessee. And if they were, and they were planning to put a wood stove in it, the wood stove decision isn't a dollars and cents decision. Instead, many folks here live in existing houses, of varying degrees of airtightness and insulation, and they have an existing furnace of some sort (or no furnace at all). And for those folks, there's no way that going out and buying a new high efficiency heat pump will have a positive ROI on any timeline versus wood heat.

So it really comes down to whether we're talking about a person who already has such a heat pump (and probably has a somewhat efficient house) or would need to factor the upfront cost into the calculation.

 

[Max W]

ROI can be pretty short with rebates and tax credits. Maine through Efficiecy Maine has begun offering the new rebates on mini splits. 80%up to $8000; 60% up to $6000 and 40% of prject costs up to $4000. The three are based on low, moderate and no income limit eligibility. Moderate income is considered up to $100,000 for joint filers, 70,000 for single.

 

[Max W]

ROI can be pretty short with rebates and tax credits. Maine through Efficiecy Maine has begun offering the new rebates on mini splits. 80%up to $8000; 60% up to $6000 and 40% of prject costs up to $4000. The three are based on low, moderate and no income limit eligibility. Moderate income is considered up to $100,000 for joint filers, 70,000 for single.

I edited this post a few minutes after posting. The ones up are the correct %’s

 

[Prometeo]

the heat pump system
it has no thermal mass,

do we should say something about ?
For example the heat is retained less,
thanks all

 

[Duds13]

Curious how those in the northeast this weekend with a heat pump and no backup woodstove faired with no power and single digit temps at night. Bet it wasn't fun

 

[stoveliker]

Most in the northeast have oil back up?
(And the little pump in there is easily ran by a 2 KW generator in conjunction with the fridge...)

 

[Highbeam]

Most in the northeast have oil back up?
(And the little pump in there is easily ran by a 2 KW generator in conjunction with the fridge...)

My "giant" 24k btu heat pump also has no problem running on a small 240 volt generator's power. It's an inverter so power quality is not very important. If the heat pump could make enough heat in single digit temps on line power, it can do it on genny power.

 

[begreen]

My "giant" 24k btu heat pump also has no problem running on a small 240 volt generator's power. It's an inverter so power quality is not very important. If the heat pump could make enough heat in single digit temps on line power, it can do it on genny power.

How has that worked out for the family this year?

 

[stoveliker]

My "giant" 24k btu heat pump also has no problem running on a small 240 volt generator's power. It's an inverter so power quality is not very important. If the heat pump could make enough heat in single digit temps on line power, it can do it on genny power.

I have a 36k btu heat pump, and my generator doesn't give me 240 V. And I think that's common?

 

[begreen]

I have a 36k btu heat pump, and my generator doesn't give me 240 V. And I think that's common?

Yes, true for many. Our current generator is just 120v. It all depends on what one needs. If one has a well and/or a pump up septic system then a 240v genset capable of running those systems in an outage is needed for power outage running. With power management, a Honda or Champion 6.5kW genset may be able to run the system. Our 3 ton heat pump is about 3.3kW start up and 2.7kW running. It's 2006 tech so I would think a modern 3T inverter system would work even easier on a genset.

I see the prices of Chinese gensets keeps coming down. This one will provide 7.6kW continuous.

9500 Watt SUPER QUIET Inverter Generator with CO SECURE Technology

Amazing deals on this 9500W Co Secure Inverter Generator at Harbor Freight. Quality tools & low prices.

www.harborfreight.com

How frequent are long power outages on your part of Long Island?

 

[stoveliker]

Not so frequent; twice a year or so. 2 days when the last tropical storm hit (forgot the name) a few years back. Mostly a few hours, so that the fridge stays cool enough if one manages when one opens it.
All manageable.

In TN it was far worse; longer lines per customer (lower pop. density), so more trees in between, and strong thunderstorms. Bought the generator there after we got kids (can't let milk/lactation in the freezer go bad). Used it at least 5 times a year.

 

[Wisco Shepherd]

We just finished building and have a wood stove, in floor heat, and 2 Mini splits with heat pumps. If I am ever cold its my own damn fault but I will say the wife likes the wood heat most so you can guess which direction we lean.

 

[begreen]

In TN it was far worse; longer lines per customer (lower pop. density), so more trees in between, and strong thunderstorms. Bought the generator there after we got kids (can't let milk/lactation in the freezer go bad). Used it at least 5 times a year.

That is more like our situation. We're fortunate that our water is gravity fed from a very large system tank with about 7 day reserve capacity. With the wood stove for heat and a gas cooktop, refrigeration is a primary need. Our 2.4kW generator easily covers all needs.

I do love the heat pump. It heats the house well and affordably down to about 32º, though I am burning wood when the temps are below 40-45ºF. We'll probably upgrade in the next few years to a modern inverter heatpump with better low temp performance, but I don't think we'll change the generator.

 

[stoveliker]

Exactly the same here.
2.2 kW generator, fridge, few lights, microwave OR espresso machine (essential needs, after all ;-). ) And a fan in summer.
I can easily do that for half a month. The propane bbq has a cooking section next to it. Additional propane tank always full.
The generator was $200 and is dirty... so it only runs after 6 hrs of power outage, and then not continuous, just an hour on, 4 hrs off.

In winter the stove heats the home (I can run the fan sucking cold air from the living room and depositing it on the bottom of the basement) on the same generator as it's 26W. And the minisplit if it's below 45 for 24 hrs or more, though it can supply enough heat for my home when it's 17 F outside. It's not a hyperheat, but I was impressed by what it can do. Of course below 20 F it goes to a COP of 2-ish.

Water I'm not sure; tower nearby, but it's never been out. (Trembling for the next (my first) real hurricane...)

 

[Highbeam]

I have a 36k btu heat pump, and my generator doesn't give me 240 V. And I think that's common?

Your heat pump surely requires 240volts and that is very common on the 5000 watt and up open frame generators but very uncommon on inverters gensets. I have both types of genset because most of the time I am perfectly happy with a small, gas sipping, very quiet, very clean power, 120 volt inverter. For running the well, resistance hot water heater, and heat pump I'll need to roll out the gas hog 240 volt genset.

If I lived in the far north and had no non electric back up heat then you can bet I'd figure out a generator that could run my heat pump and it's really no big deal. They're very common and low priced.

 

[Highbeam]

How has that worked out for the family this year?

We have used the heat pump for heating during those few extra warm periods this winter when it is too warm to burn a clean fire but too cold to go without heat. It works. It's nice and quiet and barely bumps our electric consumption at all. My family, including the dogs, prefers the wood hearth heater.

No burn bans for a couple of years either so haven't needed to use it for that.

Heat pumps are pretty great. I keep waiting for something to break but it doesn't. Always ready to go.

 

[ShaneMac]

Installed a new Gree Flex 3T last fall and the temps dropping to -20C my power bill only went up $100 a month. To test it out I barely used any wood this year. Only using the stove when I felt like it, not when I needed it. Has me wanting to replace the new to me Regency F3500 with a new secondary burner to have better visuals with the stove due to not being a primary heater and worrying about wood efficiency. Wood is still cheaper for me though due to only burning dead fall on the property.

 

[Dix]

Exactly the same here.
2.2 kW generator, fridge, few lights, microwave OR espresso machine (essential needs, after all ;-). ) And a fan in summer.
I can easily do that for half a month. The propane bbq has a cooking section next to it. Additional propane tank always full.
The generator was $200 and is dirty... so it only runs after 6 hrs of power outage, and then not continuous, just an hour on, 4 hrs off.

In winter the stove heats the home (I can run the fan sucking cold air from the living room and depositing it on the bottom of the basement) on the same generator as it's 26W. And the minisplit if it's below 45 for 24 hrs or more, though it can supply enough heat for my home when it's 17 F outside. It's not a hyperheat, but I was impressed by what it can do. Of course below 20 F it goes to a COP of 2-ish.

Water I'm not sure; tower nearby, but it's never been out. (Trembling for the next (my first) real hurricane...)

A word to the wise.... get yourself some plastic water cooler bottles w/ caps. Fill & forget. You'll be able to flush (judiciously ) I have about 6 3 - 5 gallons each. Walmart.

Also some gallon bottled water ( I have 4-5), and a couple of cases. Rotate as needed

 

[Sticker]

All things considered, heating with an electric heat pump system is not more expensive than wood, what do you think?

Depends. Price of wood, efficiency of wood stove, efficiency of heat pump? My primary source of income in life is analyzing efficiency in HVAC products. So I may have over thought some of this by this point in life.

I also throw in an initial cost component, labor (time) spent to operate and expected life cycle(depreciation) as well as annual maintenance and repair.

I'm located in central Ohio. My belief is heat pumps are great for heating down to just under 50 degrees outdoor ambient. I do not like to heat with them once they begin to cycle into defrost mode, as the supplement heat from gas or electric used during the defrost cycle is a killer of overall efficiency. So at 45 degrees I switch to 91% efficient gas furnace. I installed a 1000 gallon propane tank in order to buy gas once per year at discounted late summer pricing. The additional cost going from a new 500 gallon tank to a new 1000 gallon tank was a mere $1,000 and the capacity difference of 400 vs 800 gallons has saved me over $300 /year so in 4 years the extra initial cost was eliminated.

Once temperatures reach 20 degrees or colder I fire up my high efficient wood stove with a CAT . I'm actually not convinced the CAT stove was a good idea at this point, as many stoves reach similar efficiency when burned properly at the upper end of their thermal capacity. I thought I would burn more in shoulder season which is why I went with the CAT, but since I can not smoulder the wood it gets the house too warm, so heat pump it is for mild weather.

I say all that to say this, yes, in most cases in mild weather (50 or above) , heat pumps are excellent sources of heat both in ease of use and cost per btu. In cold weather, I still pencil gas or wood out as far superior looking at my inputs. Geothermal has the continuous advantage of heating with warmer ambient from water, and has a huge cooling advantage during the summer, but even with all that efficiency advantage the initial cost is prohibitive.

 

[EbS-P]

Depends. Price of wood, efficiency of wood stove, efficiency of heat pump? My primary source of income in life is analyzing efficiency in HVAC products. So I may have over thought some of this by this point in life.

I also throw in an initial cost component, labor (time) spent to operate and expected life cycle(depreciation) as well as annual maintenance and repair.

I'm located in central Ohio. My belief is heat pumps are great for heating down to just under 50 degrees outdoor ambient. I do not like to heat with them once they begin to cycle into defrost mode, as the supplement heat from gas or electric used during the defrost cycle is a killer of overall efficiency. So at 45 degrees I switch to 91% efficient gas furnace. I installed a 1000 gallon propane tank in order to buy gas once per year at discounted late summer pricing. The additional cost going from a new 500 gallon tank to a new 1000 gallon tank was a mere $1,000 and the capacity difference of 400 vs 800 gallons has saved me over $300 /year so in 4 years the extra initial cost was eliminated.

Once temperatures reach 20 degrees or colder I fire up my high efficient wood stove with a CAT . I'm actually not convinced the CAT stove was a good idea at this point, as many stoves reach similar efficiency when burned properly at the upper end of their thermal capacity. I thought I would burn more in shoulder season which is why I went with the CAT, but since I can not smoulder the wood it gets the house too warm, so heat pump it is for mild weather.

I say all that to say this, yes, in most cases in mild weather (50 or above) , heat pumps are excellent sources of heat both in ease of use and cost per btu. In cold weather, I still pencil gas or wood out as far superior looking at my inputs. Geothermal has the continuous advantage of heating with warmer ambient from water, and has a huge cooling advantage during the summer, but even with all that efficiency advantage the initial cost is prohibitive.

Do you have access to a crossover temp calculator? I know they exist.

 

[Sticker]

Do you have access to a crossover temp calculator? I know they exist.

I know of a crossover temperature calculation, designed to find the spontaneous combustion temperature of an exothermic reaction.

Could you possibly mean changeover calculator, where you enter cost of fuel, efficiency and such to arrive at the proper changeover temperature going from one source to another?

 

[Prometeo]

Depends. Price of wood, efficiency of wood stove, efficiency of heat pump? My primary source of income in life is analyzing efficiency in HVAC products. So I may have over thought some of this by this point in life.

I also throw in an initial cost component, labor (time) spent to operate and expected life cycle(depreciation) as well as annual maintenance and repair.

I'm located in central Ohio. My belief is heat pumps are great for heating down to just under 50 degrees outdoor ambient. I do not like to heat with them once they begin to cycle into defrost mode, as the supplement heat from gas or electric used during the defrost cycle is a killer of overall efficiency. So at 45 degrees I switch to 91% efficient gas furnace. I installed a 1000 gallon propane tank in order to buy gas once per year at discounted late summer pricing. The additional cost going from a new 500 gallon tank to a new 1000 gallon tank was a mere $1,000 and the capacity difference of 400 vs 800 gallons has saved me over $300 /year so in 4 years the extra initial cost was eliminated.

Once temperatures reach 20 degrees or colder I fire up my high efficient wood stove with a CAT . I'm actually not convinced the CAT stove was a good idea at this point, as many stoves reach similar efficiency when burned properly at the upper end of their thermal capacity. I thought I would burn more in shoulder season which is why I went with the CAT, but since I can not smoulder the wood it gets the house too warm, so heat pump it is for mild weather.

I say all that to say this, yes, in most cases in mild weather (50 or above) , heat pumps are excellent sources of heat both in ease of use and cost per btu. In cold weather, I still pencil gas or wood out as far superior looking at my inputs. Geothermal has the continuous advantage of heating with warmer ambient from water, and has a huge cooling advantage during the summer, but even with all that efficiency advantage the initial cost is prohibitive.

Thank you, the product I would like to install, ducted, has a COP of 3.7 the distance between the motor and internal unit is 30 feet and I don't know if this can reduce the COP, and how much. If COP reduction would be notifiable, I would probably install 3 splits, one large and 2 small, with the engine practically on the wall opposite the split. Here the costs per kW seem to be decreasing, currently we are around 15 cents, so I am very inclined towards this type of heating. Also because the temperatures lately rarely reach freezing levels, my plan would be to turn it on in the morning, continuously until the evening, and turn it off at night.

 

[begreen]

And for those folks, there's no way that going out and buying a new high efficiency heat pump will have a positive ROI on any timeline versus wood heat.

Mostly correct except for this statement. If one has to buy their wood and electricity is affordable, then the numbers work out, especially in a milder climate, and more so with modern super high-efficiency heat pumps.

We're in an old farmhouse that had a high-efficiency propane furnace when we moved in. Every year propane costs escalated until a decade later, the cost to heat the place solely by propane would have exceeded $3000/yr. In 2006, the furnace was pulled out and a high-efficiency heat pump system was installed. I also installed a new chimney and woodstove in a central location. Electical rates were about 9¢/kWh. We let the heat pump handle the house for a November to compare billings. That month's electrical cost was around $90 IIRC which included dryer, fans, lighting, etc.
I was able to scrounge a lot of wood and we had some big trees taken down on the property but that costs some and I had to buy a splitter so the wood heating costs needed to be amortorized over several years but in the end we went from over $3000/yr (and rising annually) to about $500/yr for heating with wood and the heatpump during shoulder seasons.
Fast forward to today. I'm getting old and the boys are now off on their own, so it's just me and my wife. We still burn with wood when it's below 40º but are relying on the heat pump more. Wood now costs us around $400 a cord and electricity is about 11¢/kWh. The heat pump in this old farmhouse has definitely paid itself off and is less expensive to run than the wood stove. Still we burn because we like the fire and the radiant heat from the stove is hard to beat.

Our heat pump was the best we could buy 18 yrs ago, but I suspect we will be replacing it soon with a new unit. I will invest in the best I can afford. This will probably outlast me, but that's ok, it will help the resale value of the house if nothing else.

 

[Sticker]

Thank you, the product I would like to install, ducted, has a COP of 3.7 the distance between the motor and internal unit is 30 feet and I don't know if this can reduce the COP, and how much. If COP reduction would be notifiable, I would probably install 3 splits, one large and 2 small, with the engine practically on the wall opposite the split. Here the costs per kW seem to be decreasing, currently we are around 15 cents, so I am very inclined towards this type of heating. Also because the temperatures lately rarely reach freezing levels, my plan would be to turn it on in the morning, continuously until the evening, and turn it off at night.

Will the line set of your split system heat pump run through a conditioned space the entirety of the 30 feet or will it be in unconditioned space like an attic ? In either case, a well insulated line set will protect against a drop in efficiency. Heat transfer in a conditioned space is not near the issue of degrading efficiency as heat transfer where none is intended.

Some of this is strictly preference, but I personally like the mini splits when possible.