Geo Thermal / Heat Pumps
there are many types of heat pumps all do basically the same thing absorbing heat from another body and and condensing it. Be it a Air to Air , Air to Water, Water to Water or Water to Air. General in North America we use Air to Air or Water to Air. the reason for is that most homes in north America use a forced air heating/cooling system. else were in the world they use air to water and water to water systems because they use a radiant heating system. which is more efficient. we are not talking radiators ( like stream radiators) we are talking more about in floor radiant ( like the Romes used 2000 years ago). the biggest advantage to this is the lower temperature required and a lower energy requirements to keep a house warm.
The Air to Air and Water to Air heat pumps general have a higher COP then Water - Water or Air to Water. but they generally have to run at higher temperatures thus over all reducing their efficiency for heating.anything other then air.. general COP of these units are 3.3 - 6
The Water to Water or Air to Water heat pumps have a COP that ranges from 2.4 to 6. My Personal Water to Water heat pump has a COP of 4 at 55C
Air Sourced Heat Pumps
while they are sold in Canada are not particularly suited for our climate. they are cheaper to install, but their efficiency quickly drops off as it gets colder outside and basically stop working around -15c . if you are get one of these only get it if you live in a part of Canada that does not get very cold. because otherwise it basic function would be that of an air conditioner only and not really for heat
Ground Sourced Heat Pumps
These types are the best choice in Canada they are more suited to our climate and you will achieve the best energy savings. there basically 3 types of ground sources.
Well to Well: probably the the most efficient with the highest COP but cost to install is much greater and so is up keep.
Closed Ground loop Vertical: probably the most expensive route to go. but if you have limited ground space it may be your only option
Close ground loop Horizontal: the cheapest way to go. but requires a lot of ground space. it COP is variable better in the fall / earlier winter but poorer in the late winter and onwards. but because it installation and upkeep is considerably lower then the two mentioned above it is usually the best route to go.
Closed Ground loop Horizontal plus Solar Water Heaters: Cost is probably equal to Well to Well but the energy saving is extremely significant. requires a smaller heat pump and 4 or more solar water heater ( 4 kw or more) one will see for 7- 8 months out of the near 100% of their hot water needs are "free" and 4 months out of the year the reduced by +50%. plus boosting the efficiency of their ground loop heat pump to that of a well to well and greater having COP in fall and spring time in 5-6 range and in the deep winter averaging out at about 3- 4 COP for those months