[atqtion]

> you can't heat your home with a heat pump in a place like Wisconsin... Geothermal is better, though I believe you still have problems with saturation in cold climates

Geothermal heat pumps can definitely work in the portions of the upper midwest. I know some people in both MLK and Madison that have heat pumps.

As far as I understand it's hit and miss, though. Depends on the particular piece of property you're living on. And you may need an additional heat source for occasional use (e.g. the super cold winter a couple years back I know one of those folks were super glad they still had gas heating in addition to the heat pump).

> I hadn't even heard of a heat-pump until recently, which makes sense, since they seem to mostly be concentrated in warm, dry areas.

Ironically I'm the other way around. Didn't hear about heat pumps until moving north. Probably because heat pumps don't make as much financial sense in warmer climates where you're not blowing $100+/mo on heat?

[Declanomous]

I think we are talking about two different things. Everyone I know with geothermal heat pumps just call them geothermal. What I have heard called heat pumps are basically air conditioners that can also be used to heat the home.

Until recently I had no idea the air conditioner-like heat pumps existed, and it appears that they are only useful if you live in a place with a low dew point and relatively high minimum temperatures, since they can ice pretty easily and don't work well below a certain temperature.

Anyways, Most of the people I know with geothermal in Wisconsin have fairly large tracts of land, and still need to supplement with wood pellets or something similar. I'm not sure you could fit enough of the heat exchange loops in a typical yard in a densely populated area.

To be honest, the last time I did the math was probably about 10 years ago, but I recall vertical systems are really not cost effective if you have access to a city natural gas system unless you really like AC.

That being said, I'm renting right now, so I haven't kept close tabs on recent developments.

Edit: Also, I think heat pumps are installed in warmer climates because a dual-purpose AC that doesn't heat that well is cheaper than installing a separate fossil fuel based system, which would be overkill as well as much more expensive.

[hx87]

Air source heat pumps have become much more efficient at lower temperatures than they used to be. The best units from Mitsubishi, Fujitsu, Gree, et al, put out their nameplate rating down to -13 to -20F, and continue to produce >50% of their output at COP > 1 below -30F. For new construction, or if you need to replace your current boiler/furnace for some reason, heat pumps always beat gas in levelized cost unless gas is extremely cheap compared to electricity in your area.

> unless you really like AC

Given changes in climate as well as obesity rates, more and more people will really like AC as time goes on, even in the coldest places.

[toomuchtodo]

My air conditioner in Tampa has a reverser valve to run as a heat pump when it's cold out; it'll run down to 0F using only the air source condenser unit.

[Declanomous]

My understanding is the limit to the heating potential of a heat pump system is the evaporator freezing over, which is why they are more popular in areas with low humidity. I think at a certain point the heat pumps spend so much time in defrost mode with the auxiliary heater running that they aren't economical.

[hx87]

Wintertime humidity is rarely if ever high enough for frost buildup to be an issue--it's the humid shoulder seasons that have this problem, but your heating/cooling needs during those seasons aren't that high anyway, so defrost cycles won't lower comfort and efficiency all that much.