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Air source heat pumps draw air across an evaporator heat exchanger to heat homes and water.

They are an ideal choice where a ground source heat pump isn’t possible or desirable and can run in conjunction with an existing traditional boiler system.

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We often get asked if heat pumps work in cold weather - the short answer is yes!

Your heat pump will keep your home warm even when the mercury plummets below zero. 

However, with little to no warm air to use as energy the efficiency of your heat pump won't be up to much during really cold snaps. Because the unit is using more electricity than normal to produce the same amount of heat. 

It's worth keeping in mind that the co-efficiency of performance of a boiler at ALL times is less than 1 and that this blip in your heat pumps efficiency is offset by the generally fantastic co-efficiency of performance (CoP) that a heat pump will manage during the slightly warmer months (anything over 0 degrees) - anything between 3 and 5!

In layman's terms, a boiler is about 85-95% efficient. For every one unit of fossil fuels/grid-energy used you get less than one unit of heat back.

A heat pump is about 300-500% efficient meaning for every one unit of grid-energy used you get 3-5 units of heat back (because the heat pump supplements its efforts with the warm air from outside)!

We call this a CoP (Co-efficient of Performance). 

Here's a summary from one of our happy clients during the UK's most recent -11 degree cold snap!

"Hi Joe,

For your information, during last week's exceptionally cold spell, down to minus 11 degrees centigrade overnight, the RED ASHP coped. 

Pleasingly, the lounge radiators worked well, maintaining a warm environment even on the coldest days, although we did supplement this with the wood burner in the evenings, as much for visual comfort.

As might be expected, as the temperature dropped, daily electrical consumption increased, from circa 24Kw/h @ +10 degrees, 46Kw/h @ 0 degrees to 73Kw/h @ -10 degrees. CoP obviously dropped too, although the average is still high.

Kind regards,



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