irc wrote:roubaixtuesday wrote:irc wrote: Only a few years ago we had a winter with sub zero temps for days on end. No heat to exchange.
This is a fundamental misunderstanding of thermodynamics.
An over simplification. But plenty reliable sources say air source heat pumps are less efficient as it gets colder. If back up electric heating needs to be used it will get expensive.The amount of heat that can be transferred to you home by an air source heat pump is massively reliant on the outdoor temperature. As the temperature outside drops, so does the overall heat output of the air source heat pump.
The heating capacity of the air source heat pump also tends to drop as the outside temperature decreases. The air source heat pump is typically sized to be able to produce heat for 80-90% of your annual load, and when the temperatures are above freezing, it should be able to fill 100% of the heating requirements for your home.
As a result of this, it is recommended that you have a backup source of heating available for when the outside temperature drops. This way, it is able to pick up the slack when your air source heat pump starts to decline in efficiency.
https://www.renewableenergyhub.co.uk/ma ... d-weather/as the thermometer fell, the bills went up. He was getting about 100 kilowatt hours of heat for each 100 kilowatt hours of electricity he used. This means that in cold weather the unlucky householder is spending eight or nine pounds a day on electricity (multiplied up, £250 a month) but, even more strikingly, he would be better off if he simply installed a few electric heaters in the main rooms. In fact, if I were advising him, I’d say he should turn off the pump whenever outside temperatures fall below about 7 degrees.
https://www.carboncommentary.com/blog/2 ... ld-weather
Yes, heat pumps become less efficient as the temperature difference becomes larger. The efficiency is defined as "coefficient of performance", COP.
This is not the same as "no heat".