It is what it says on the tin. That's the amount of kilowatts needed to heat your home and provide your hot water. As to why other homes are less, they might be better insulated, use less hot water or run the heating less.

@batalto hmmm .... two hours of central heating a day during the winter months is not exactly on the high side. No heating from April to October. Sparing on hot water use too following an electrical fire 3 years ago. So what it says on the tin is not reality. Presumably it’s what they think we should be using. 

Have you tried one of the heat loss calculators? I posted one on here a while back. You can do room by room heat loss assessment as that would be the bulk of your heat loss. Your boiler might also have a problem and not be working efficiently - for example mine is only running at 58% so it's eating gas. Can't seem to find a reason, but no point fixing it. Once I worked out the heat demand and the efficiency losses the EPC loss, heat assessment and my use tied up pretty closely.

@jennyross, as @batalto says it's an estimate of the annual kWh needed for your heating and hot water. I think what you're asking is how is it calculated and how accurate will it be.  

It's done by the EPC surveyor using the EPC sofware on their tablet.  It's based on some factors they input like size of house, construction details, insulation and ambient weather (based on your postcode).  It doesn't take any account of your personal habits and details like number of occupants, whether you have lots of hot baths, how hot/cold you like your house, etc.  Divide it by 365 to get your average daily use, although it will be a lot more in winter that summer.  

As you've found out, different EPC surveyors can come up with different answers because they make different assumptions about construction and insulation.  Some surveyors are good and some aren't and sometimes it's genuinely difficult to determine whether a house has, for example, an insulated floor or not.  They should all be able to measure your house accurately though, but even that's not guaranteed. 

As I said, it's just an estimate and two identical houses with identitical EPCs could have vastly differing actual usage; that's down to the occupants.  But from an RHI point of view you want the number to be as high as possible because the amount you get depends on it (although it is capped at 20,000).

22,000 is not particularly high and is a good number to have because it's near the RHI cap.  Half that would be very low. A good test to check if it's accurate is to multiply it by your current kWh energy cost and see if it matches what you actually pay.  This is a good source of these costs but you can tweak accordingly.

NOTTENERGY.COM "https://nottenergy.com/resources/energy-cost-comparison/"

@batalto thank you. That's helpful. We are 100% electricity. No gas. Our electric boilers (we have two) and hot water tank were disabled by 50% three years ago following a fire caused because they had been incorrectly installed by the previous occupiers. We have been considering an ASHP since then. 

Were we to maintain a warm house during the winter months in this part of Scotland - where temperatures routinely dip below minus 10 in Jan/Feb - then our monthly heating bill would be in the order of £450-550 (our neighbours have paid up to an eye-watering £700 a month) which is completely unsustainable for us. 

I'll try the heat loss calculator and see how I get on. I have heat loss calculations for each room - provided by different potential installers. The EPCs are all pretty similar in terms of heat demand. 

@kev-m Thank you - all helpful. Our current usage is about half the electrical demand cited on the EPCs. We pay for c. 11,000 kWh annually - but that's because we don't use the wet electric central heating when we should. ..and most of the house is, well, cold. Cold means sitting at around 10 degrees. We have a wood burner and so we are not completely without warmth - but the situation, reliant on electricity as we are, is far from ideal. See my reply to @batalto also. 

@jennyross if you are all electric then an ASHP seems a no brainer as its going to be more efficient per kw used. A standard electric induction is 100% efficient (for augments sake) if your ASHP is 250% efficient then you should lower your bills considerably. With the other houses, are they also running on electricity for heating and hot water?

@batalto Yes - we've consistently been told it's a no brainer.... although the cynic in me doesn't always respond well to those words! We're not needing to make a decision about whether or not to install an ASHP. That decision is made. The issue for us is which installer to trust and which ASHP.

@batalto the other house owners on the estate are all running on electricity only for heating and hot water. Two have installed new electric radiators; one installed oil last year; the rest continue with their electric boilers. 

There are also some new builds on the estate (since last year) and they have ASHPs installed.

Hi Jenny,

It may be beneficial to have a chat with the new build owners, to see what ASHP's they have and their experience of that particular manufacturer.

@derek-m the choice of heat pump for these new builds is Vaillant.