We recently installed an air source heat pump to heat our house. If you heat yours with electricity from the grid, and if the structure isn’t divided into many small rooms, then a heat pump will cut your power consumption so dramatically that the whole $2500 installation pays for itself in two years. And power consumption equals environmental footprint.
It’s quite a fascinating technology, and friendly to the environment too as long as you don’t rupture a pipe and release circulation fluid. You know a fridge? An air source heat pump makes your house into a fridge turned inside out.
Heat is movement among molecules. At absolute zero, molecules are still and there is no heat. What a fridge does is it removes heat from the inside of the cabinet and deposits it outside, in effect heating your kitchen ever so slightly at the expense of the food-spoiling microbes’ comfort inside. A heat pump attempts to refrigerate the outside world, depositing the harvested heat inside your house. Whether the temperature’s freezing outside is irrelevant: as long as it’s not absolute zero out there (which is rare even in Stockholm, Sweden), you can get all the heat you need.
In the summer, you can shift the thing into reverse mode and use it as an air conditioner. I’m in awe!