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I'm investigating the most efficient way to heat my new 2000 sq home in New Hampshire and am having some difficulty working out the math based on the numbers I have found.

I've found that wood is incredibly cheap...even if I buy it late in the season when the prices have gone up. I'm looking at $350 a cord for mixed hardwood, which I found can produce 22.1 mBTU.

I've also found an 89% efficient insert, increasing the cost savings per month to $116 for wood over oil. These savings are HUGE. If my numbers are right I'm jumping on the wood burning wagon immediately.

--Edit--

Going further down this rabbit hole, I've update the image with new specs for the heat pump, and I'm also wondering if those are correct. What I'm seeing is that a SEER 16 heat pump is 4.689 times more efficient than standard electrical heating, which means that a 48k btu 4 ton system can give me 16000 btus per kWh vs the standard 3412 btu/kWh of electric resistance heating.

Does that calculation make sense? Are heat pumps and wood inserts really that much better than oil? Can I really save 178 dollars a month by going with a 16 SEER heat pump?

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  • Varies by location, and may not inclde all associated costs (such as the vague cost of lack of automation). Here is one state's independent crunching of the numbers (which will be slightly different from yours) over a number of years: publicservice.vermont.gov/publications/fuel_report pay attention to the section where they "Compare cost of heating fuels" for a fixed number of delivered BTUS in the monthly reports. – Ecnerwal Oct 4 '14 at 21:06
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    You also have to take into consideration, actually getting the heat from the fuel and into the house. A wood burning fireplace is not likely going to heat an entire house evenly. Unless you plan on installing a fireplace in every room, or a central wood burning stove, it's going to be difficult to heat an entire house. You'll also have to spend a lot more time tending the fire. – Tester101 Oct 4 '14 at 21:34
  • @Tester101 I have a whole house fan with the return in the same room as the fireplace. Do you think that could work to help transfer heat around the house? – JMD Oct 4 '14 at 21:35
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    Maybe, it's hard to say without seeing the layout of the house. I was just trying to point out that the cost of fuel is not the only thing you have to consider. You also have to think about the cost of spreading the heat throughout the house, and how to extract the heat from the fuel. – Tester101 Oct 4 '14 at 21:38
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    Wood heat also reacts slowly to changes in outdoor temperature. If you get a warm day where heat is not required, an oil furnace can be turned off. With wood, you lose all the wood that is already in the fire. And you're producing heat when you don't need it, until the fire burns out. This is why most people use wood as an additional source of heat, not the primary source. – Tester101 Oct 4 '14 at 21:51
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You're right, but only because oil is the worst, most expensive way to heat a home. Pretty much anything beats it, except maybe electric resistance in places with high electricity prices. Wood, gas, and heat pump electric will all beat the pants off oil. That said, even 80% efficiency may be optimistic for a modern high efficiency wood stove. But even if that's overstated, as you can see, it's still a pretty good deal.

Additionally, your calculations may even be understating the advantages of a heat pump. 1.4 as the coefficient of performance is very conservative. I'd use 2, especially given how they not have high-efficiency units on the market than can deliver their rated performance at -15f. Some can go as high as 3 or 4 during periods of non-frigid outdoor temperatures and less than peak internal load.

Edit: you said, "Does that calculation make sense? Are heat pumps and wood inserts really that much better than oil? Can I really save 178 dollars a month by going with a 16 SEER heat pump?"

Yes indeed. But again, only because oil is such an awful fuel. Anywhere in the USA, one therm of oil heat is several times four times as expensive as one therm of natural gas heat, simply because of the relatives prices of oil vs natural gas. If you were comparing a wood stove and an electric heap pump to natural gas, it would get a whole lot more complicated--especially in the cases of a 95% efficient gas furnace, or a state with low gas prices or high electric prices.

No matter what you choose, do your wallet and the planet a favor and heat with something other than oil! It's expensive, it's dirty, and (IMHO) it contributes to awful foreign policy. Just Say No!

Edit 2: Some gov't verification of your numbers: http://www.eia.doe.gov/neic/experts/heatcalc.xls

  • I had looked at the Regency CI2066 as en example and saw it was 79% efficient, looking again I see many are much lower efficiency (and cheaper). As for the heat pump, unless I was to pay upwards of 12k for a 20 SEER heat pump (and spend 20 years waiting for it to pay off), I'm stuck with a 16 SEER ducted unit that comes in at around 1.4. The other issue is that heat pumps only really work until 35 degrees unless I get a ducltess minisplt from Mitsubishi (mucho bucks) which would then work to -15. – JMD Oct 4 '14 at 20:04
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    Ductless minisplits are not actually mucho bucks. You can get one for 3k or less; check out younits.com. Way less than the 12k you seem to have been quoted for a central unit! That said, the price will rise if you need multiple heads. But it's possible to get ducted minisplit units that aren't too expensive; the caveat is that you need good ductwork for them to work. But you could spend the money you'd save on that! :p – iLikeDirt Oct 4 '14 at 20:19
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    However, there's another major advantage to a wood stove: it will probably last for 100 years. It's not a complicated electro-mechanical device that can easily break and require professional repairs that has a definite service life measured in years rather than decades or centuries. For this reason, I always prefer to go with dumb-as-dirt technology if it will get the job done. – iLikeDirt Oct 4 '14 at 20:24
  • I currently have very good, modern ductwork that the previous owner installed for a 10 SEER AC unit. That's why I'm attracted to the thought of having a kickass 20 SEER heatpump installed. If I could get a 2.0 efficiency for < 6k installed I would be pretty happy. – JMD Oct 4 '14 at 20:37
  • Also, I think you're right, my math may have been off on the heat pump...The unit I'm looking at is SEER 16 and 4 ton, which can produce 48,000 BTUs. I then divide the BTUs by the SEER to get 3000. This is the number of watts it takes to produce that 48k BTU, so I then divide by 1000 to get the kilowatts, which is 3. So dividing 48k by 3 tells me that I get 16k btu/kWh. Does this make sense? Because if it does, then the coefficiency ends up way way higher. With a normal electric heater I am at 3412/kWh, which means my 16k/kWh is 4.68 times more efficient....can this be true? – JMD Oct 4 '14 at 21:01
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a heat pump has a cop or coefficient of performance. Your 48000 BTU Heat pump delivers that much heating nominally with mild temperatures outside.. To see how much power it uses you divide by COP and then convert to kWh. In my area natural gas is about half the cost of baseboard heating, and heat pump heat is half the cost of gas heat. In the winter it is not 2x more like 1.3, but often a heat pump is sized for the cooling load so the heat pump can't keep up. If you can, use the oil or gas option for backup heat in the winter and that will get you the most savings with a heat pump setup

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