Ground Source / Geothermal Heat Pumps and Other Info

It depends on the heat pump. If you get a mini-split, and have decent insulation, they can work down to -20C: * [link] * [link] * [link] Some folks using them in Alaska: * [link] If you get a heat pump that looks like the 'traditional' external AC unit (giant cube), those tend to work down to about +5C. Not sure how much more they cost above a 'regular' air conditioner: * [link] The Technology Connections channel has a couple of interesting videos on the topic of heat pumps: * [link] * [this video] He has a video entitled "How to calculate when heat pumps make financial sense (and other heat pump follow-up thoughts)": * [link] NR Canada has a "AIR-SOURCE HEAT PUMP SIZING AND SELECTION GUIDE": * [link] Financially speaking you're going to have to break out a spreadsheet and plug numbers in: (natural) gas prices, electricity prices, efficiency of the units, etc. Doing a search for "heat pump calculator" may get you started.

They are great if you are looking to use electricity to heat because they are 3 to 4 times more efficient than resistive heaters. It depends on the price of electricity and other heat sources in your area. If you live in the north where temperatures go below -15 Celsius, air-to-air units aren't as great because they lose efficiency as it gets colder outside. My heat pump has a COP of 3, meaning it can generate as much heat as a resistive heater using 1/3 the electricity, but it shuts off at -15 Celsius because below that point it is less efficient than resistive heat. If your heat pump has a COP of 4, you might get to -25 Celsius before it is less efficient than a resistive heater. Better, but more costly, heat pumps use in-ground water, either from a pair of wells, or from a deep pond that won't freeze to the bottom, or from many meters of water pipe buried deep enough beneath your lawn to not freeze in the winter. Because of the depth, they always have access to the earth's heat so they don't lose efficiency in the winter. The Technology Connections YT channel has a couple of good videos about how them: 1. [link] 2. [this video]