Bedrock, soil, exhaust air, lake water and outside air heat pumps
Heat pumps are often described by the way of extracting energy. Thus a bedrock heat pump extracts heat from the rock (water running and trickling in the fissures in the rock) and an outdoor air heat pump extracts heat from the outdoor air.
The difference in principle of where to extract the heat is depending on the amount of heat that can be extracted. A bedrock heat pump extracting heat continuously from the running water in the fissures nearly always keeps a temperature above zero degrees Celsius. If the flow is bad it could result in the water freezing, the ice (insulation) then deteriorates the heat extraction. This can not happen to a ground water heat pump with enough flow of water from the well.
A soil heat pump extracts heat from the earth by freezing it, due to this it performs less the longer a cold period is. This is also the case when using a lake heat pump if the lake water is not circulated.
An outdoor air heat pump is very dependent of the temperature outdoor and its efficiency drops substantially during a cold period. Even though you save a lot it is important to keep auxiliary heating as oil, electrical, wood and so on when the temperature drops, this applies on all heat pumps.
When choosing the size of the heat pump it is important that it covers 50 to 60 percent of the maximum necessity of heat and thereby covering 80 to 90 percent of the annual need of heating.