EPC worse after installing solar and new windows

[SquashedSquashess]

Since purchasing our property we’ve installed solar panels and a battery, and replaced all of the wooden doors and windows (which were starting to rot and were draughty) with PVC windows and doors.

We had our EPC rating renewed yesterday. When we purchased the property it was a 63D. Our EPC rating is now 67D. Apparently this is because of a new methodology.

We are in the process of trying to sell, so it’s particularly frustrating to find that all of those works have had no effect on the EPC, and somehow its score has gone down!

If we can’t sell we will need to think about letting it and renting where we live, as we’re moving for work. By 2030 letting it out will not be an option as all properties then need to have an EPC of C or above.

Interested to know if anyone understands how this decreased score could have occurred under the new methodology, or has any experience successfully appealing an EPC rating.

Wow that is bonkers 🤡

I get you're thinking why the hell did we bother. Though I guess the EPC woukd be even worse with the new methodology if you had not done any of that work.

I dont think it will affect the sale too much, i dont think buyers give a shiny shit about EPC ratings. The goverent think we do..... but i dont know anyone who paid attention to it when buying a house and I certainly didnt.

In general I wouldnt put solar panels on a house unless I was going to stay there a long long time. It is a bit like an extension; based on current house values I have only "made back" 75% of the cost of my extension in four years... it takes a while.

if I was buying I wouldn’t be bothered by the EPC

My current house has an EPC C rating because of the ASHP it’s an ancient inefficient thing costing far more than other peoples boilers to run

I dont pay much heed to these scores, the fact that they even mention switching to energy saving light bulbs to improve your score shows they are an out of date joke.

Nobody will care and hopefully you're too far from 2030 to worry about it

Ours went from like e to b when we changed the lightbulbs. We had assumed new owners were capable of changing lightbulbs but there you go.

Change all bulbs/fluorescent tubes to LEDs.

Presumably the rating would have plummeted if you hadn't had the work done. So you aren't worse off.

"When we purchased the property it was a 63D. Our EPC rating is now 67D."

This means your rating has gone UP by 4 points. It has NOT gone down.

I'm surprised no-one else has mentioned this.

Home batteries at the moment do not improve the EPC rating, due to the way the assessment methodology values electricity exported to grid, versus electricity imported from grid (caveat: assuming you have an export capable meter and no PV diverter - Google some relevant keywords and you'll find more details).

Solar PV should give a decent improvement so long as you have documentary evidence of the array kWp etc. and it's connected to the electricity supply of the property. What is the kWp of your installation by the way?

Replacing wooden doors with new uPVC - Doesn't ordinarily make any difference to the rating. A small fractional improvement will be experienced if the old door wasn't draughtproofed, and the new one is (always the case with uPVC nowadays), and a further small improvement can also be experienced when fitting a new door to an older property so long as documentary evidence is available of the u-value of the door, and the assessor manually overrides the u-value in the new assessment. See why in the "RDSAP 10 Specification document" publicly available online - it's down to the u-values, and the small area of doors (1.85m2 each) compared to the much larger area of other building fabric such as walls and roofs etc.

Replacing wooden framed windows with uPVC - You don't mention whether the old windows were single or double glazed, which is more important that the frame type, although frame type plays a part. The greatest improvement comes from replacing single glazed with double or triple glazed. If you already had older double glazed windows though, then replacing with new double glazing or even triple glazing will generally not make a significant difference. Again, this is down to the u-values (which can be overidden for high-performance glazing btw), and the area of windows compared to area of other building fabric such as walls etc.

I should tell you that EPC assessments do not record the condition of items.

There are occasional methodology updates to make assessments more accurate including the update to RDSAP 10 on 15th June 2025, which included a number of changes including compulsory assessment of all windows individually, the more detailed recording of ventilation, and the way that room-in-roof (aka loft conversion) is assessed. However, this wouldn't be the first place I would be looking if I were concerned about an EPC rating not turning out as expected though.

Bear in mind there are things that can bring an EPC rating down which most homeowners will not be aware of, and I wonder if this could be the case. Examples include changing the thermal separation of a conservatory, changing heating systems (even to the latest best 'efficient' electric panel heaters), changing a mixer shower to an electric shower, adding certain ventilation systems such as DMEV, PIV from loft, etc. I also wonder if your earlier EPC was from new-build (unlikely with old wooden frames), or whether there is any discrepancy with floor area between the two EPCs?

If you wanted to paste in the features table from the two EPCs I could comment further but in terms of making a complaint I think you'd need something solid to base that on. You can't be certain for example the initial EPC was correct can you?

This will not have been down simply to changing the lightbulbs. Lighting has such a small effect on the EPC rating.

The EPC recommendation for "low energy lighting" appears if this measure would make at least a 0.5 point improvement to the rating.

Most normal people would say it would be a joke if such a recommendation was not available in the methodology or presented on EPCs.

I forgot to add that you can request a copy of the assessment data used to produce your EPC, from the assessor - you might reasonably need to pay perhaps £30 extra for 'admin'.

If you are methodical and prepared to spend time searching through that data and look up online anything you need to understand the meaning of, you might be able to spot any oversights.

You can look up your EPC online. It tells you exactly what you need to do to boost up. How many points you get for each little thing