Air Source Heat Pump - how much should I expect to pay on energy bills?

Damob123

Verdigris said:

What does your EPC say the heating requirement is? You can look it up online, if you don't have it to hand? Also what power rating is the heat pump and what is the SCOP (that will be on your RHI calculation)?

We just had a new EPC done (after the heatpump had been installed), and states the following:

- Estimated heat usage (space heating): 11173 kWh
- Estimated heat usage (water heating): 2755 kWh

MCS certificate states:

- Estimated heat usage (space heating): 10729 kWh
- Estimated heat usage (water heating): 2198 kWh

The heatpump power rating is 8.5 kW with a SCOP (what's SCOP?) of 3.65. It's a Mitsubishi Ecodan.

Reed_Richards

SCOP = Seasonal Coefficient of Performance
This means that averaged over a year (all four seasons) you would expect to achieve 3.65 kW of heat for every 1 kW of electricity.

Damob123

Reed_Richards said:

SCOP = Seasonal Coefficient of Performance
This means that averaged over a year (all four seasons) you would expect to achieve 3.65 kW of heat for every 1 kW of electricity.

Makes sense - thanks! However, is that not abit contradictory of our estimated heat usage vs our actual usage?

So we've got an estimated heat usage (space and water) of roughly 13,000 kWh and our actual usage over the last year is roughly 6,500 kWh. So actually our SCOP is 2.0?

Sorry if it's a daft question, I'm just trying to get my head around it.

matelodave

If your estimated energy usage from EDF is 6500kwh then I'm guessing that some of it is being used to cook, clean, wash etc.

My total energy consumption is around 8000 kwh but 3500-4000kwh of that is for other uses rather than heating so 4000-4500 is for heating. My EPC calculates a requirement for 12500 kwh for heating and 2500kwh for hot water. which roughly equates to 15000/4500 = a SCOP of around 3.3

Reed_Richards

Damob123 said:

Reed_Richards said:

SCOP = Seasonal Coefficient of Performance
This means that averaged over a year (all four seasons) you would expect to achieve 3.65 kW of heat for every 1 kW of electricity.

Makes sense - thanks! However, is that not abit contradictory of our estimated heat usage vs our actual usage?

So we've got an estimated heat usage (space and water) of roughly 13,000 kWh and our actual usage over the last year is roughly 6,500 kWh. So actually our SCOP is 2.0?

Sorry if it's a daft question, I'm just trying to get my head around it.

If you have had a heat pump for year and you get the RHI then you have a meter that tells you exactly how much electricity your heat pump has used.  If you bothered to record it you will also know your actual total electricity usage for the last year.  If I understand what you wrote correctly, then 6,500 kW is only an EDF estimate.

The SCoP for heating your hot water won't be as good as for your central heating.

In my case my MCS estimated heat and hot water requirement is 18870 kWh and I used 6930 kWh in a year so if the estimated requirement is correct then my SCoP is only 2.72.  However my EPC reckoned I needed about 21000 kWh per year.

QrizB

Damob123 said:

So we've got an estimated heat usage (space and water) of roughly 13,000 kWh and our actual usage over the last year is roughly 6,500 kWh. So actually our SCOP is 2.0?
Sorry if it's a daft question, I'm just trying to get my head around it.

Your 6500kWh/yr includes electricity for non-heating, non-HW purposes. A typical household might use 2-3000kWh/yr on lighting, cooking, TV/audio, PCs, games consoles and all the other gubbins of modern life.

If 2500kWh of your 6500kWh was "other stuff" that would mean you''ve used 4000kWh for heat & HW and your COP is 3.25.

As R_R says, if you're getting RHI payments you will have a meter that measures exactly how much electricity your heat pump has used.

Verdigris

A quick mental calculation from all the above suggests the heat pump is going to cost about £1100 per annum, including a proportion of the standing charge and assuming you don't get any benefit from the Economy 7 rate. Sounds fairly reasonable, to me. And then you'll have your RHI payments to play with.

markin

Most efficient way to run underfloor heating

https://forums.moneysavingexpert.com/discussion/6219931/most-efficient-way-to-run-underfloor-heating/

Reed_Richards

markin said:

Most efficient way to run underfloor heating

https://forums.moneysavingexpert.com/discussion/6219931/most-efficient-way-to-run-underfloor-heating/

My theory is that you cannot run a mixture of underfloor heating and radiators more efficiently than you can run entirely radiators.  The efficiency of the heat pump decreases the hotter it has to make the water.  You usually need hotter water for radiators than for underfloor heating.  So having some underfloor heating does not give you any economic benefit over having entirely radiators.  If this is wrong I would be happy for somebody to tell me why.

Damob123

Really appreciate all the discussion and help - thanks!

Here’s another one to throw into the mix:

What are peoples thoughts on the ROI (return on investment) of installing solar with the heat pump? We get a good amount of sunshine (some of the most in the country).