Your EPC says D. Does that actually matter?

My own EPC once told me the floor was solid with no insulation. The exact wording on the certificate was "Floor: Solid, no insulation (assumed)".

The floor had insulation. I knew it had insulation. What I did not have, on the day the assessor came, was a piece of paper proving it. So the certificate says it does not.

That single line explains more about EPCs than any description of the system.

What an assessment actually is

An assessor comes round for about an hour, depending on the size of the house. They measure it and record the floor area. They note the wall construction and its insulation, the loft and roof insulation, the windows and glazing, the floors, the boiler and heating system, the hot water, the heating controls, the lighting, and any renewable technology. They look at the meter, the boiler and the loft where they can get to them. Mine cost £70 and was done by an accredited assessor.

An hour is not long enough to find out what is inside your walls and under your floors. It was never supposed to be. Where a feature cannot be verified on site and there is no acceptable evidence for it, the assessor may be unable to credit it, and the assessment falls back on the applicable convention or default instead. Insulation is the example the guidance itself uses: without something like a receipt, a claim that it is there may not make it onto the certificate.

The way out is paperwork. Installation certificates and guarantees are what count.

So two genuinely identical houses can get different ratings. Same walls, same loft, same boiler. One owner kept the folder and one did not, and the one with the folder scores higher. That is not a criticism of the assessors, who can only record what they can verify in an hour. It is just worth knowing what the number is actually measuring.

I did eventually find the document for that floor. I never bothered having the certificate redone.

Does anyone actually look at it?

In my experience, no.

I have sold houses and no buyer has ever mentioned the EPC, asked about it, or asked me to improve it. No lender or valuer has ever raised it with me. When I have been buying, I have looked at the certificate and not paid it much attention, and I have never seen a rating poor enough to change my mind about a house.

If something on the certificate were badly misleading a buyer, that would be worth saying. The reality is quieter: the rating is not misleading anybody much, because nobody is leaning on it.

It exists because you need one to sell. That is the real answer to why you have one.

By comparison, building control paperwork matters enormously. That is the paperwork a solicitor asks about, that a survey raises, and that can move a price. An EPC has never done any of those things to me.

So spend on the bills, not on the score

If you are living in a house for the next ten years, do not spend money to move a letter on a certificate. Spend it on what the house costs you to run. Those are two different jobs and the second one is the one you feel.

The clearest example is radiators. I replaced old ones with newer, slightly larger radiators that held their heat far longer. The bills came down. As far as I can tell the rating did not move at all.

What has actually made the difference to running costs across the houses I have owned is unglamorous. Lights, which cost me about £150 to do throughout in LEDs. Good radiators. Decent windows. And fixing leaks, both water and air.

The air leaks are worth a paragraph, because they cost almost nothing to find. Mine were around the windows and at the points where they join the wall. I found them by standing there and feeling the air come in. No equipment, no survey. The bills moved afterwards. I never measured by how much, so take that as an observation and nothing firmer.

Draughtproofing and heating controls do something real. They are near the bottom of most recommendation lists and near the top of what actually works. Double glazing works fine for most homes. Triple glazing is an extra with small additional benefits, and it is not the place to start.

Solar, and why I have not fitted any

I have not put solar on any house I have owned, and the reason is the up-front cost against how long it takes to get back.

I worked mine out at around fifteen years. Plenty of published figures are a good deal shorter, and the gap is not really a disagreement about solar panels. Payback depends on the installation cost, electricity prices, how much the roof actually generates, how much of that you use yourself rather than export, what the export payments are worth, and how the whole thing is financed. Change any one of those and the answer moves by years. If your house is empty from eight until six, the self-consumption assumption alone is doing a great deal of work.

Two things are worth knowing before you take a number off a page. The payback shown on an EPC is indicative, worked from standardised assumptions rather than your household's actual consumption. And simple payback, wherever it comes from, is a blunt measure: it says nothing about maintenance, financing costs, or anything that happens after the break-even point.

This is not an argument against solar. run the numbers for your own house and your own day, and to ask which assumptions any payback figure was built on before you lean on it.

Where to start

Get the certificate, because you need one to sell.

Dig out your paperwork first, so the thing is at least accurate about the house you own. It costs nothing and it is the only part of the rating you can improve without spending money.

Then forget the letter and spend on the bills.