Advancements in cold climate heat pump efficiency.

[begreen]

In terms of quality - how do you rate Daikin and Fujitsu? Mitsubishi?

All good. I rarely hear bad words about them. The Fujitsu 1 ton units went in early locally and folks love them. The only problem I have heard about is that they are power outage/voltage surge sensitive. Surge protection is a worthy investment.

 

[Brian26]

With record high oil and gas prices heat pumps will bring some huge savings to some this winter. Here is a look at Maine. I go the fuel prices from the states heating fuel tracker and used the EIA average electricity price(.17) in the state.

Per million BTU.

Propane at $3.21. $45.76
Heating oil at $3.5. $29.12
Heat pump at COP of 4. $12.46

Heating Fuel Prices | Maine Department of Energy Resources

The Maine Department of Energy Resources (DOER) conducts a survey of heating fuel prices obtained from delivered fuel retailers statewide. This survey provides the current Maine cash prices, in dollars, rounded to the nearest penny. Prices are updated each week during the heating season...

www.maine.gov

 

[peakbagger]

Kind of an overly simplistic comparison especially for Maine. The COP for heat pumps you use is overly optimistic, even with the latest and greatest tech the COP plummets as temps go down as the heating load goes up. I agree there are savings but in order to come up with an estimate there is going to have be a comparison of design temps and heating load versus actual COP at design temps. A COP of 2 is better than resistance heat but probably a better average for winter heating. Realistically even the state admits that heat pumps are not primary heating sources unless equipped with a supplemental heating source. So any estimate would need to blend in electric resistance heat, Kerosene, natural gas, propane or heating oil for periods below zero when heat pumps really start to have tough time putting out reasonable temperature heat at a low COP.

I am involved to some extent with large commercial and institutional projects in Mass that sell thermal recs from heat pumps (air and geothermal) savings and we consistently are seeing that real world heating efficiency is less than predicted on these buildings and backup heat is needed more often in cold weather. The owners are not happy but they just pass the costs onto tenants.

 

[Brian26]

Kind of an overly simplistic comparison especially for Maine. The COP for heat pumps you use is overly optimistic, even with the latest and greatest tech the COP plummets as temps go down as the heating load goes up. I agree there are savings but in order to come up with an estimate there is going to have be a comparison of design temps and heating load versus actual COP at design temps. A COP of 2 is better than resistance heat but probably a better average for winter heating. Realistically even the state admits that heat pumps are not primary heating sources unless equipped with a supplemental heating source. So any estimate would need to blend in electric resistance heat, Kerosene, natural gas, propane or heating oil for periods below zero when heat pumps really start to have tough time putting out reasonable temperature heat at a low COP.

I am involved to some extent with large commercial and institutional projects in Mass that sell thermal recs from heat pumps (air and geothermal) savings and we consistently are seeing that real world heating efficiency is less than predicted on these buildings and backup heat is needed more often in cold weather. The owners are not happy but they just pass the costs onto tenants.

I was going off a HSPF of 12-15 which equals out to a COP of around 4 for the course of a heating season. Those HSPF's numbers are common on heat pumps purchased the last few years. Maines heat pump rebate even requires a 12 or higher hspf to qualify for the bigger rebate.

 

[peakbagger]

The problem with HSPF is published figures are for zone 4 heating which is fine for CT but Maine NH Vt and NY is zone 5 and arguably Northern Maine, NH and VT should be a zone 6 (if one existed). It great for comparing units just like EPA mileage figures but there are too many assumptions baked into it to calculate actual energy use.

I get it that you live in CT and you are in great location for minisplits but you need to be really careful to misrepresent a minisplits capabilities in a colder climate than you experience. There is big institutional and political bandwagon to get these installed for legit reasons everywhere including Maine NH and VT and in general they tend to over sell minisplits in very cold climates. The realists are not getting paid the big bucks to point out the potential issues and a result the media ignores them since they dont buy big media buys . As supplemental heating in cold climates during shoulder seasons and warm days I am right with you (mine is running today at 30 F) but there is big pool of practical experience out there that they just do not make it as primary heating source during temps much below 20F in typical older housing stock. Yes they will run down lower but then you start running into the Quality of Heat issue which is far more subjective. Homes are drafty and a typical minisplit high wall installation leads to temperature stratification in room. That means a higher set point temp compared to radiant or baseboards (pretty common in colder climes) Sedentary folks sit lower in a room and frequently near windows that are sources of drafts. Baseboards tend to be located under drafty windows so the effect of the windows is lessened to some extent. That problem is opposite with minisplit, the heat from the minisplit tends to be sent to the center of the room with quite a hihg volume. The high fan speeds recomended to get the maximum efficiency out of the heat pump are loud enough to be annoying to many folks and the high fan speeds tend to drop the exit air temp. Unless we want to bring up entropy a BTU is BTU but to homeowner 10,000 cfm of tepid air a couple of degrees above room temp is worth a lot less than a lesser amount of 100F air coming out of hot air system. So the typical homeowner approach is to crank up the setpoint.

 

[EbS-P]

COP17 is a good number that I think is meaningful for Mainers. Again I don’t see heatpumps as a stand-alone heating system for cold climates yet. bJanuary average temps for Bangor are 26 high and 9 low. Coldest morning I woke up it was -30F. How much heat can you pump out of -20 to -30 air?

But with a heatpump thoughtfully run, I imagine it could cover 1/2 -3/4 of your heating needs. Which is meaningful. I imagine oil prices will see a steady increase over the next decade. (I think electricity prices will also increase to cover infrastructure expansion/upgrades but not by as much as oil).

 

[peakbagger]

I agree that it will easily cover 1/2 to 3/4 of the heating load but that means the homeowner has to keep their backup heating system operational. As I have mentioned in the past, I know of a supplier of vented#1 heating oil heaters that is selling a lot of them for that purpose. They are strictly space heaters but they do not take much power to run on generator if the power goes out and they throw out a lot of heat for their size.

 

[Brian26]

I think I read that like over 60% of Maines population lives either along the coast or in the Portland area. I choose Maine as the state publishes weekly data comparing fuel costs. It looks like the state uses a cop of around 3.5 for heat pumps.

Residential Heating System Cost Calculator | Efficiency Maine

Our heating cost comparison calculator can help you estimate your annual home heating costs for different heating systems.

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