How to predict heat pump size from your EPC

[Sparrowhawk]

18 minutes ago, ProDave said:

I don't know how it is calculating that heat loss, but it is certainly NOT reading any actual figures from the EPC you select.

It is - it read the data from the one when we bought this house and calculated the heat loss correctly. Going through the "I need to make changes to this process" came close to  the spreadsheet calculating where I'm aiming for.

For typical UK housing (knackered and draughty) it seems to work fine.

[saveasteading]

47 minutes ago, ProDave said:

heat load of 7.4kW

Isn't that based on the coldest day, which is already an extreme case?

 

[ProDave]

4 minutes ago, saveasteading said:

Isn't that based on the coldest day, which is already an extreme case?

 

My real extreme case coldest day is just over 2kW

 

I have just tried it again, selecting the option to change things, and there is only gives very coarse options like insulation over or under 200mm no mention of type or U value so it is clearly NOT reading the actual values from the EPC.

 

Oh and at the end of inputting the values there was no "proceed" or done option, so it never did manage to give me a revised figure.

 

Sorry a broken / not properly tested website that either spits out meaningless values or does not work at all.  

[JohnMo]

9 hours ago, sharpener said:

about Shrunkpunk

Just tried the link

 

Even though the full heat loss calculation in the SAP report says 3kW heat loss, the shrunkpunk says 8.7kW, no idea where it's getting that info from?

[sharpener]

On 07/11/2024 at 10:07, ProDave said:

Oh and at the end of inputting the values there was no "proceed" or done option, so it never did manage to give me a revised figure.

 

Sorry a broken / not properly tested website that either spits out meaningless values or does not work at all.  

 

Yes, very deficient. Tried it again just now, sometimes the Next button was not there, sometimes it did not work.

 

It would be useful to see what info it drags out of the EPC. I suspect not much or it would already know the floor area when you try to modify things.

 

CBA to try and reverse engineer it any further but agree it could be a lot better. Tried Good Energy estimator, seems to download floor area and type of house from EPC, not much better though, quotes me for 2 x 12kW Midea, £20700 less grant, not remotely competitive.

[ProDave]

1 hour ago, sharpener said:

seems to download floor area and type of house from EPC,

Yes I got the impression this one just determined the age and it was (in my case) timber frame and then applied typical values for a new build timber frame of that era, totally ignoring the actual as built data contained in the EPC.

 

I don't have a lot of faith in the EPC system and in 10 years time when my as built full SAP EPC "expires" I bet if we ever wanted to sell we would not be able to get anything other than a silly guesstimate next time.

 

I am not expecting this house to be sold until I am in a box, so I won't worry about it too much.

[JohnMo]

8 minutes ago, ProDave said:

got the impression this one just determined the age and it was (in my case) timber frame and then applied typical values for a new build timber frame of that era, totally ignoring the actual as built data contained in the EPC

That's strange when I went into it, came up with my floor area, and all the U values and came up with a strange kW required. Refering to the SAP report the TER (target emissions rated) wasn't even as high as the quoted figures.

 

It also stated I would need a new EPC, even though the one I have is only a year or so old.

[ProDave]

Yes it did show floor area and average U values of walls etc, then went on to calculate a ridiculous high figure, so having pulled that data from the EPC and displayed it on my screen, it must have then gone on to use something else to calculate the heat load.

[SteamyTea]

4 hours ago, sharpener said:

suspect not much or it would already know the floor area when you try to modify things.

The EPC I had done showed double my floor area.

Still gave me a C, just like my neighbours.

 

 

[S2D2]

The heat geek website has a similar tool, it will also bring up the epc rating and floor area so you can sanity check it has the right epc. Sit down before you read the price though.

 

I've been through the mill on getting an MCS install over the last year and hit all the issues mentioned here, the epc that came with the house and all of our quotes were based off was out on heat demand by about 50%, mostly due to the previous owner having an electric radiator in the conservatory which meant it was flagged as a habitable room.

 

I'd suggest using the heat punk design tool (not shrunk punk, the full heat loss design) because it allows you to have multiple radiator/flow temp profiles for the same property. Do one with absolutely strict MCS air changes/temps etc. and a flow temp of 50, which octopus install to. This is your absolute best case scenario for getting the BUS grant, I found no reasonably priced MCS installer would go below it. This took me a while to accept because for me MCS gives a heat loss of 5.8kW, whereas in reality we sit at around 3.5-4kW based on gas usage data. Our MCS surveys varied between 6.2-6.8kW, down to 5.8kW after going through the detail with one surveyor. They will accept photographic proof of any fabric improvements.

 

You can then copy the MCS profile with more realistic ACH/temps and see how low you can get the flow temp. Second time round with Octopus they agreed to oversize the radiators (don't ask to reduce the flow temp, they won't) by around 50% which means the system will actually run at 42C flow temp no issues.

 

I've accepted an 8kW Daikin R32 unit after ruling it out a year ago. It's the 4-8kW unit so apparently able to modulate well down to about 300W electrical input. I would not accept the 9kW unit. I did have a promising quote with eon for the arotherm plus 7kW but they were obsessed with adding in second radiators and in the end £3k more expensive than Octopus, so 10-20% efficiency difference is irrelevant at that point.

 

I was fixed on the Vaillant 5kW but the final nail in that coffin is they removed the 250L tank from the compatibility table, so the combination is no longer possible under MCS.