But a heat pump can move more heat with a therm of electricity than resistance heat can create with same therm. Likely can move more heat than created by a therm of gas in most cases as well.
If you do a quick Google on "gas furnace efficiency", you'll see (for new) between 92% and 96%. Even my bottom-of-the-line unit is 90%, according to the test the tech did.
Highly unlikely, and certainly unlikely at a COP below 2.
For the cost of one mini-split system that covers one room, you can put in a gas furnace that will heat your whole house.
Actually, kwired statement was obviously true whenever COP was above 1.
I don't know about that.... I think it's really hard to generalize and come up with a statement like that there are many variables.
Okay yes I concur. I was mixing up stove type heaters versus condensing type heaters.
Maybe if the forced air ducting is in place already. But in that case you could put in a mini-split that supplies a high pressure air handler. Or a conventional central heat pump. Given that the heat pump supplies A/C also, I would expect it to compare not unfavorably with a gas furnace plus A/C in terms of cost and performance.
Not so fast! I have heard that CA is getting rid of all Natural Gas appliances. I know NY is going down that road. I have heard that CA is even outlawing small engine gasoline tools like lawn mowers and chain saws.
Which is why they sometimes put an outdoor thermostat to lock out the compressor when COP drops too low. There is no point in getting a heat pump if it will never see conditions above 1. There are places where COP will drop for cold spells but then go back to a COP that is still going to cost less to operate than if you only used your backup heat source.
Thats an incorrect statement. They are only phasing it out of new construction.
A typical residential gas furnace from a house built in the 80's is probably 60% efficient, its not like everyone has the latest greatest gas furnace.
I dont see the distribution losses of the gas infrastructure to the homes in that calculation.
That might be true in places that don't get all that cold. Around here is somewhat rare to find one that old. If you do chances are it has a bad heat exchanger and is a CO hazard but occupants don't know it. Heat exchanger gone bad is a main reason majority of them have been replaced to begin with.
You are confusing the issue. The issue is what does one therm of gas deliver at the furnace vs what does one therm of gas deliver as electricity? Converting that therm of gas to electricity gets you about 38% of the energy value at the heat pump. That's why you need a COP of ~2.4 or over to break even.
I read "a therm of electricity" to mean 29.3 kWhs. If you read it as "the kWhs you'd get from burning a therm of gas in a modern generating plant" then that would explains some of the confusion.
Agree on the 2.4 calculation being approximately correct. Disagree on the earlier "unlikely" statement. COP of 2.4 or above is typically the case.
That would not be the correct approach. You have to take the electricity losses into account in this analysis because you are converting one form of energy into another, and efficiency is important.
geothermal is usually pretty inexpensive to operate (compared to other options) but often rather expensive to install. Ductwork, the unit itself are same or similar as many other options to install, but you also need wells, ground loops, etc. unless you are in a location where you have an abundant supply of water that is not too difficult or costly to set up to circulate through your system.
