Understanding Energy Performance Certificate (EPC) calculations

[DundeeDancer]

Maybe I’m missing understanding these EPC calculations are doing but they currently don’t make sense to me and I wonder if they make more sense to others?

 

I’ve just looked at a EPC for a neighbours flat that just went on the market this week and the calculation goes like this:-

 

Page 1
Dwelling type: Mid-floor flat 
Date of assessment: 20 February 2023 
Total floor area: 95 m2 
Primary Energy Indicator: 234 kWh/m2/year

 

Page 3
Space heating (kWh per year) 12,707 
Water heating (kWh per year) 1,992 

 

Page 3 seems wrong to me, for Space heating should it not be Total floor area: 95 m2 * Primary Energy Indicator: 234 kWh/m2/year to = 22,230 kWh per year?

 

Gas boiler in flat is probably 80% efficient, so per year for combined water and space heating one would be using approc. 29,066 per year. 

Usual energy estimates are for 3 years so that would be 87,200 kWh and current gas prices per kWh are 10p so that would be £8,719 for space and water heating not including general electricity use but the estimated energy cost for 3 years given on the EPC is £5,934, seems well short to me.

So the £ estimate being off I’m not to surprised at but the simple calculation from floor space to yearly space heating should be bang on at 22,230 kWh per year and not 12,707 kWh?

Also when I bought my apartment which is very similar to the flat above, my EPC stated the Primary Energy Indicator was to be: 132 kWh/m2/year, so that’s a big difference, turns out 234 kWh/m2/year is fairly accurate as I did use 22,000 kWh in my first year of staying here. I’ve managed to get that down to around 16,000 kWh with new boiler and single room MVHR but still far in excess of the promised 12,936 kWh on the EPC which came on the home report when I purchased the appartment. 

 

Best wishes, DD 😎
 

[JohnMo]

Trouble with EPC on older buildings can be rubbish in rubbish out.  The assessment is basically what is or isn't seen or assumed.  Unless they are corrected by the home owner, the rubbish output remains.

 

But I have to say 95m2 mid floor flat using that much energy needs some work to reduce the heat losses.

 

[nod]

The EPC assessment is very general 

We use a chap that charges £30 per property 

[jfb]

On 24/02/2023 at 22:12, nod said:

The EPC assessment is very general 

We use a chap that charges £30 per property 

Do you have a contact for him?
do you know what is a typical charge for an epc for a new build (actually a 70m2 barn conversion)?
or is that a slightly different thing that needs SAP calculations?

[Dave Jones]

4 minutes ago, jfb said:

Do you have a contact for him?
do you know what is a typical charge for an epc for a new build (actually a 70m2 barn conversion)?
or is that a slightly different thing that needs SAP calculations?

 

yep needs SAP as well. Paid £450 for last one.

[jfb]

Just now, Dave Jones said:

yep needs SAP as well. Paid £450 for last one.

So the epc and sap are separate things?
I had an ashp install that had all the energy demands calculated  - would the company that did that effectively have a sap report for the property? Wondering if it is worth chasing them up to see if I can get a copy!

[Dave Jones]

doubt it. sap is for building control and the output of it is an EPC.

[Mike]

On 24/02/2023 at 19:13, DundeeDancer said:

Page 3 seems wrong to me, for Space heating should it not be Total floor area: 95 m2 * Primary Energy Indicator: 234 kWh/m2/year to = 22,230 kWh per year?

Primary energy = the amount of energy burnt at the power station. A lot of that energy is lost in waste heat at the station and in transmission losses, so a very different figure from the kWh measured on your meter.

 

[ADLIan]

Full SAP output is used to show Building Reg compliance and create the EPC for new build dwellings. Full SAP calc is also needed for new dwellings created by conversion but normally only to issue the EPC (sometimes needed for Building Reg compliance too).

EPC is needed as part of BC sign-off.

[Post and beam]

On 24/02/2023 at 22:12, nod said:

We use a chap that charges £30 per property 

F***, I just paid £90 for an EPC so that i can sell my current house before i start to build. That appears to be the going rate around here. Northern home counties.

[ProDave]

22 minutes ago, Post and beam said:

F***, I just paid £90 for an EPC so that i can sell my current house before i start to build. That appears to be the going rate around here. Northern home counties.

Bargain if that is all you have to spend to market a property.

 

I have just spent £650 for a home report, a requirement in Scotland to market a property.

[saveasteading]

A proper epc takes hours to prepare, and knowledge of the construction, boiler efficiencies etc.

The output is then a summary of multiple factors, with fairly arbitrary loadings attached to them. (These are changing at last eg gas is good, all buildings use cooling).

My business invested in the program and a lot of training so we understood where the flaws were. But then still had to pay an independent company to do it again for every new building.

 

For £30 or £90 you are getting a piece of paper based on negligible input and standard house construction. 

 

Depends what you need and want.

 

We did a conversion from a small barn to be a store with small office. 40mm composite cladding . No floor insulation. Our Client got his own assessment for renting it out. Very cheap and a B rating, whereas it was clearly only a D at best.

It worked for him. Whether the assessment was incompetent or cheating (what rating do you need) I have no idea. 

 

A family member was offered a free energy rating by the electric supplier. Totally pointlessly but to tick  a box. He spent 5 minutes in the house. When told of added insulation and draught proofing he said that was of no consequence and not of interest...Victorian terrace therefore based on standard construction.

 

If selling, do what you want.

If buying, dont trust the epc/sap.

[Post and beam]

The guy that did ours was in the house for no more than 15 minutes. I think it was/is pointless but a legal requirement.

[saveasteading]

10 minutes ago, Post and beam said:

I think it was/is pointless but a legal requirement.

And obviously uncontrolled and in the hands of opportunists.

When / if people eventually understand the value of good insulation, then perhaps this will become regulated.

[Mike]

6 hours ago, saveasteading said:

When / if people eventually understand the value of good insulation, then perhaps this will become regulated.

 

Under the new (2021) rules in France, if the EPC is inaccurate the buyer / renter can now sue the seller / landlord for damages - probably (according to the legal advice) for the cost of bringing the property up to the declared EPC standard + reimbursement of excess fuel bills + interest, though AFAIK there hasn't been a case yet. Of course the commissioner of the report can in turn can pursue the assessor. Unsurprisingly, you can't get an EPC for €30.

 

Edited March 31, 2023 by Mike

[saveasteading]

I'd be surprised if the £30 merchants have any insurance (or morals).

It would rather concentrate their minds, and those of the estate agents.

 

I wonder what the tolerance is for 'inaccurate'?

[Temp]

https://www.telegraph.co.uk/news/2023/03/31/homes-poor-energy-ratings-faulty-modelling-ucl/

Quote

Homes given poor energy ratings on the basis of faulty modelling

 

There are several flaws in the energy performance certificate system, says University College London study

 

Houses in the lowest bands G and F were found to use 48 per cent less energy in the real world than estimated by the modelling used to rate them, University College London found.

 

The findings point to several flaws in the energy performance certificate (EPC) system, which the Government has said it will rely on to force landlords to make net zero improvements to their properties.

 

The Government has proposed that landlords will have to get their properties to at least EPC C by 2028.

 

If they fail to get their ratings to the proposed level, landlords could face fines of up to £30,000.

 

However, most homes even in lower bands have been found to already be running at EPC C levels in real-world conditions.

 

Continues..

 

Quote

 

There are also concerns that the EPC system could be holding back improvements needed to get to net zero, in particular installing heat pumps, because of the cost of electricity.

 

Jan Rosenow, an energy expert at the Regulatory Assistance Project, saw his EPC certificate drop from a D to an E even after installing a costly air source heat pump system.

 

“The EPC software overestimates the energy use from the heat pump by a very large margin in my case, so massively overpredicted how much it would use,” he said.

 

Despite having better insulation, including triple glazing, wall insulation and floor insulation, his home in Oxford was given a lower rating than his next-door neighbour.

 

 

 

 

 

 

[Mike]

EPCs certainly have significant flaws, but

 

16 hours ago, Temp said:

Houses in the lowest bands G and F were found to use 48 per cent less energy in the real world than estimated by the modelling used to rate them, University College London found.

At a guess, partly because people cap their heating use and live with lower temperatures due to affordability.

 

It's interesting that the article is using the criticisms alongside the rumour that the Government is considering easing the requirements on renting lower EPC banded properties.