Working out Air Source Heat Pump running cost?

I think we need a bit more info. Are the consumption figures you are giving for the ASHP alone or for the whole house.

Is the ASHP on a seperate meter or have you got in on the day rate of an E7 tariff or some strange complex metering system. As Cardew says 21p a kwh is insanely high what tariff are you on. I'm moaning about having to pay 11.55p/kwh to run mine.

My ASHP cost very little to run in the summer but iit can look quite expensive in the winter but I reckon mine uses around 3000-3500kw a year which equates to between £350 and £400 a year.

As it responds to the house heating requirements and it has weather compensation it's consumption can vary between 10-50kwh in a day depending on how cold it is outside. That's anywhere between £1-£6

You can only determine what it's using by continuously monitoring it's consumption.

Energy consumed by the heatpump will be measured in kwh, ie if it uses 1kw and it's on for one hour then it's used 1kwh. Your leccy meter measures in kwh

Heat energy produced by the heatpump is also measured in kwh and is done by using a heat meter which measures the temperature of the water going into the heatpump, the temperature of the water leaving the heatpump and the volume of water flowing through the pump. These are integrated together which results in the quantity of heat produced by the pump.

The COP of the heatpump is ithe difference between the energy supplied to the heatpump from the electricity supply and the heat energy output from it. So if it consumes 1kwh of leccy and produces 3.2kwh of heat it has a COP of 3.2.

The quantity of energy produced by the heatpump varies with the outside temperature and the flow temperatures so isn't a constant.

Most heatpump COPs are spec'd at 7 degrees ambient to 35 degrees flow (7/35) and a change to either of those temperrtures will result in a different COP.

If you assume that your heatpump has a COP of 3 then your 2682kwh of leccy should have produced about 8000kwh of heat which means you are paying the equivalent of around 7p/kwh during the day and about 3,6p/kwh at night assuming you get some benefit from using it from the off-peak supply.

I'm interested in how you are measuring the consumption - is it separately metered on it's own circuit, indepenedant from everything else or have you got an energy monitor connected to it?