The RHI only uses the EPC figures. You can play around with them all you like but it will make no difference. The only way to change the RHI amount would be to get a new EPC. They will not quibble or argue with you as its not you providing them, its the company which did your EPC.

@batalto I am using EPC figures (it was done last month) but how they are used will make  a huge difference to RHI figures.

My EPC gives Space Heating 16,940 kWh; Hot water demand 2,942 kWh;

A 7kw aroTHERM plus has a SCOP of 3.55.

If I input those into the RHI calculator I get - £11,200

But the system they plan to install gives a space heating demand lower than the EPC and (on paper at least) doesn't include water heating. I'm OK with that, but is this usual, will the RHI accept it? 

My installer sent me PDFs of their Design plans and the RHI Calculator

In the Design Plans PDF my installer has used only the Space Heating figure and a SCOP of 3.55 to get a RHI figure of £9,303.

In the RHI Calculator PDF the installer uses both the Space Heating AND Water Heating figures - but only a SCOP of 2.5 to get a RHI figure if £9,100.

Worst case scenario is only using Space Heating and a SCOP of 2.5 which gets an RHI of £7,700.

I'd just like to have a reasonable idea of what figure we're likely to get BEFORE we commit.

Thanks

Andy

Posted by: @andygo

Hi again

I'm about to pull the trigger for an ASHP...but before I do can someone double check the figures I've been quoted for my system to see if they make sense please?

I'm also interested in people's experience of RHI payments - any difference in the amount quoted by the installer and what is actually received.

How accurate are they? Are the installer calculations always accepted by the RHI?  Do people always get the same amount in RHI payments quoted by the installers? 

My installer, a fairly big company, say they can get it done late February so in time for the March 31 deadline. (If we don't hit that then we won't be able to afford it.)

The RHI figure they've quoted is pretty promising - more than £9k - but my fear is we get alot less than that in reality....and worse if the RHI quibble over figures supplied - will that hold up the process so we miss the RHI deadline March 31.

I find the whole RHI repayments system confusing TBH.  I thought RHI figures were based on the EPC numbers (which are fixed). But I've seen on various forums about people getting massively different RHI repayment quotes - how has that happened? 

I'm also struggling to understand the figures provided by the installer (they've given 2 slightly different RHI figures in the same quote and the design calculations don't seem to match the heating demand).

I've posted some more details below. I'd be grateful for any advice: 

According to my EPC my Heating demand is 16,940 kWh; Hot water demand 2,942 kWh;

My property is 116m2 mid terrace house rated 40E.

We have underfloor heating downstairs (26m2) and 7 radiators. 

My installer has used the EPC figures for the RHI quote - along with an SPF of 2.5. (It also says Hot Water WILL be provided.) 

That gives a RHI figure of £9,100

The system they want to put in is a 7kw (arotherm plus).

However, their Design Calculations give different figures. The Space Heating demand is 14,008 and water heating demand is 0. 

In the RHI figure calculation they still use the Space Heating figure from the EPC (16,940kw), but give the Water Heating Demand as 0 and a better SCOP at 3.55. 

This gives a RHI figure of £9,303.

Playing around with the RHI calculator I can get it as high as £11,200 if I include water heating and make the SCOP 3.55.

But if leave out water heating and bring the SCOP back down to 2.5 we'll only get £7,700.

I'm happy with having a 7kw system, personally I'd rather have it slightly undersized as we'll probably only used it for the UFH and won't have the radiators on much.

But will the RHI accept the design calculations if the installer's Design Calculations are lower than the space and water heating demands on the EPC.

Thanks in advance

Andy

 

 

Andy,

as @batalto says, the sum of the EPC heating and HW figures are used, capped at 20,000kWh.  The SCOP is the figure from the link below for your specific ASHP at the design flow temperature on your MCS calculations. 

https://mcscertified.com/product-directory/

My design flow temperature was 46C; this was the average (flow and return) temperature the radiators had to be to heat my house. The nearest value listed for my ASHP in the link was 45C to that's what was used; a SCOP of 3.77.  

That got me about £11,300.  I'd be surprised if you got much different to that.  BTW space heating and HW numbers on my MCS calculations were completely different to the EPC ones. 

@andygo as I said, they will only look at the demand heating from the EPC. what you install and its efficiency is irrelevant. They will just add up the EPC hot water and heating demand, times that by the payment per KW and that's what you get. At least that is my understanding of the system. I have the RHI and I got a maximum.

@batalto Blimey, no wonder they're changing it then! So I just need to make sure the installer includes hot water demand and uses a SCOP of 3.5..

Thanks

@andygo it doesn't matter what the installer does. As long as you have an up to date EPC you should be fine and they have all their side with MCS etc. It's only the EPC that determines what you get - if I remember correctly