Most people meet their EPC twice: once when they buy, once when they sell, and never read it in between. Then a lender, a buyer or a letting agent asks about the rating and the certificate suddenly matters. If you want to improve your EPC rating in the UK, the first step is not buying insulation - it is understanding which of the assessor’s recommendations will actually move the number, because several of them will not move it much at all.
An EPC score is produced by a standardised model, not by how warm your house feels. The assessor records what they can see and measure, feeds it into the calculation, and the score comes out. That has one very practical consequence: improvements the model recognises score points, and improvements it cannot see score nothing. Knowing the difference is the whole game.
What is actually on an EPC
An EPC runs to several pages and most of it is ignored. The parts worth your attention are these.
The rating bars
There are two coloured A-to-G bars. The first is the energy efficiency rating, expressed as a score out of 100. The second is the environmental impact rating, based on carbon emissions. Lenders, agents and regulations almost always mean the first one.
The property features table
This is the most useful page and almost nobody reads it. It lists each element of the house - walls, roof, floor, windows, main heating, heating controls, hot water, lighting - with a short description and a star rating. This is the assessor’s record of what they found.
Read it line by line and look for the word “assumed”. If the assessor could not inspect something, the software applies a default assumption for a property of that age and type, and those defaults are usually pessimistic. A cavity wall that was filled fifteen years ago with no paperwork will often be recorded as if it were never filled.
The recommendations table
This lists suggested measures with an indicative cost band, an estimated annual saving, and the rating the property could reach if the measures were done. It is generated by the software, not tailored by a human, and it frequently recommends things that make no sense for your particular house. Treat it as a starting point rather than a plan.
The three things costing most homes the most points
Every property is different, but on typical British housing stock the same three items come up again and again.
1. Loft insulation depth
This is usually the cheapest points on the board. The assessor measures the depth of insulation between and over the joists. Old properties commonly have a thin layer put in decades ago that has settled, been walked on, or been buried under boarding and boxes. Topping up to current recommended depth is inexpensive, is straightforward to do yourself in an accessible loft, and is one of the few measures where the model reliably rewards you.
The trap is boarded lofts. If you board over joists without raising the deck, you compress the insulation and lose the benefit. Raised loft legs solve this and cost far less than losing the storage.
2. Heating and its controls
The main heating system and its controls carry heavy weight in the calculation. An old non-condensing boiler, or a system with no room thermostat and no thermostatic radiator valves, drags the score down significantly.
Controls are the cheap half of this. Fitting a room thermostat, programmer and TRVs is a modest job that the model recognises. Replacing the boiler itself is a much larger decision and should be driven by the boiler’s age and condition rather than by the certificate. Do not replace a healthy boiler to win EPC points - the maths rarely works.
3. Lighting and hot water
Low energy lighting is counted as a percentage of fixed light fittings. It is the single easiest thing to fix and it is astonishing how many properties still lose points here because of a handful of halogen downlighters in a kitchen.
Hot water cylinders are the other quiet loser. An uninsulated or thinly jacketed cylinder scores badly; a properly insulated one scores well. A cylinder jacket costs very little and takes ten minutes.
The measures that disappoint people
Here is the uncomfortable truth about EPCs: the improvements that most improve your comfort are often not the ones that most improve your score, and the improvements that most improve your score are often not the ones that most reduce your bills. The model is a standardised comparison tool. It was never designed to be a retrofit plan for your specific house, and using it as one leads people to spend money in the wrong order.
Common disappointments:
New windows. Replacing single glazing with double glazing helps. Replacing older double glazing with newer double glazing usually moves the score very little for a very large sum.
Solar panels without the paperwork. Renewables can help the score, but the assessor needs evidence of what is installed.
Anything undocumented. Cavity wall insulation, underfloor insulation and rendered external wall insulation all score - if the assessor can verify them. Without evidence, they may be recorded as absent.
The evidence point is the one worth internalising. Keep every invoice, guarantee, installation certificate and photograph of work in progress. A folder of paperwork handed to the assessor at the start of the visit is worth more than any single measure you could buy on the day.
How the assessment actually works
A domestic assessment is non-invasive and usually takes under an hour for an average house. The assessor measures the property, photographs what they need as evidence, records construction type and age, notes the heating system and controls, checks loft insulation depth where accessible, and counts low energy light fittings.
They cannot open walls. They cannot take your word for an unverified improvement. They work to a defined methodology and a defined evidence standard, and a good assessor will tell you exactly what they need to see in order to record something.
Practical preparation:
Clear access to the loft hatch and to the airing cupboard.
Have the boiler’s make, model and installation paperwork ready.
Have cavity wall or insulation guarantees to hand.
When the rating actually matters
Selling. An EPC is required when a home is marketed for sale, and buyers increasingly read it.
Letting. Rented property is subject to a minimum energy efficiency standard, with exemptions in defined circumstances, and the direction of travel has been towards tightening it. Landlords should confirm the current requirement and any announced future dates rather than relying on what was true a few years ago.
Borrowing. Some lenders offer preferential products linked to the property’s rating. If you are remortgaging, it is worth asking whether your rating opens any doors.
Certificate expiry. An EPC is valid for a set period and an old one does not reflect work you have done since. If you have improved the house, a fresh assessment may be worth commissioning before you market it.
What to do in the next 30 minutes
Look up your existing certificate on the government’s Find an Energy Certificate service and check the assessment date.
Read the property features table and list every line that says “assumed”.
Go into the loft with a tape measure and record the insulation depth.
Count the light fittings that are not low energy.
Feel the hot water cylinder - if it is warm to the touch, it needs a jacket.
Start a folder for every piece of insulation or heating paperwork you can find.
The single biggest avoidable reason for a low score is missing evidence. Home+ gives you a free place to keep your EPC, your boiler and insulation paperwork, and dated photographs of work as it was done, so the next assessor records what is really there rather than what the software assumes. Store your EPC in Home+ along with everything that proves it should be better.
FAQ
How do I find my EPC? Use the government’s Find an Energy Certificate service and search by postcode. Certificates for most properties sold or let in recent years are on the public register.
How long is an EPC valid for? EPCs are valid for a set period from the assessment date, currently ten years. An older certificate remains valid but will not reflect any improvements made since, which is a good reason to get a fresh one before selling if you have done work.
What is the quickest way to improve an EPC rating? Low energy lighting throughout, a hot water cylinder jacket, topping up loft insulation, and fitting proper heating controls. All are inexpensive relative to the points they typically win.
Will a new boiler improve my EPC? Usually yes, if the existing one is old and non-condensing. But a boiler replacement is a large expense to justify on EPC grounds alone, and should be driven by the age and condition of the existing appliance.
Can I challenge an EPC I think is wrong? Yes. If you believe the assessment contains factual errors, raise it with the assessor first, then with their accreditation scheme, which has a complaints process. Errors around unrecorded insulation are the most common grounds.
