Published 1 June 2026 by Matt Fay
It's one of the most common things I hear. Someone gets their EPC back, checks the register, and discovers their neighbour next door got a C while they've come out with a D or an E. The houses look identical from the outside. Same age, same layout, same street. So what's going on?
The answer is that an EPC doesn't rate what a house looks like. It rates how it performs. And two houses that look the same on the outside can be very different on the inside.
This is the single biggest factor I see. If your neighbour replaced their boiler three years ago and yours is the original from 2005, that alone can shift the rating by one or two bands. A modern condensing boiler is significantly more efficient than an older model, and the EPC calculation weighs heating heavily because it's where most of a home's energy goes.
It's not just the age either. The type matters. A combi boiler with a programmer and room thermostat scores differently from a system boiler with a hot water cylinder and no thermostatic radiator valves. The controls matter as much as the boiler itself.
From the street, two semis look the same. But one might have had cavity wall insulation pumped in ten years ago, and the other hasn't. That's invisible from the outside, but it has a massive impact on the EPC rating.
Loft insulation is the same story. One house might have 300mm of mineral wool up there, properly laid. The one next door might have 50mm of the original stuff from when it was built, or gaps where it's been disturbed. I check every loft hatch I can access, and the difference between properties on the same street can be striking.
Double glazing is fairly standard now, but the age of it matters. Modern double-glazed units are much better than the ones fitted in the 1990s. And if your neighbour has had theirs replaced recently while yours are the originals, that feeds into the rating.
I also see plenty of houses where most windows have been upgraded but one or two haven't. A single-glazed bathroom window or a wooden-framed side door can pull the rating down more than people expect.
This surprises people, but lighting counts. If every fitting in the house is LED, that scores well. If half the house still has old halogen spotlights or bayonet bulbs with 60-watt incandescents, it drags the rating down. It's a cheap fix, but it does make a measurable difference on the certificate.
If one house has been extended and the other hasn't, the floor area changes. A conservatory with a polycarbonate roof and no heating will perform poorly. A properly insulated rear extension with underfloor heating will perform well. The EPC assesses the whole property, so what's been added and how it's been built matters.
How hot water is heated and stored plays a role. A house with a well-insulated cylinder and a thermostat on it scores better than one with an uninsulated tank in the airing cupboard. If one property has switched to a combi boiler and got rid of the cylinder entirely, that changes the calculation too.
An EPC is evidence-based. If I can see the cavity wall insulation drill holes, or the homeowner has the installation certificate, I can record it as insulated. If there's no visible evidence and no paperwork, I have to record it as uninsulated, even if it was done years ago. That's not a judgement call - it's the methodology.
This is actually one of the most common reasons for a lower-than-expected rating. The work was done, but there's nothing to prove it. If you've had insulation installed, keep the paperwork. It could save you a band on your next EPC.
Usually, yes. The EPC itself includes a list of recommended improvements and what rating you could realistically achieve. Some of the biggest gains come from relatively straightforward changes:
I've written a more detailed guide on how to improve your EPC rating if you want the full breakdown.
A lower rating doesn't mean there's anything wrong with your house. It means there are specific things that could be improved to make it more energy efficient. Most of the properties I assess across Greater Manchester come out as a D or an E - that's completely normal for the housing stock in this area. Victorian terraces, 1930s semis and 1960s estates all tend to land in that range unless upgrades have been done.
The difference between you and your neighbour usually comes down to a boiler that's ten years newer, or insulation that was done quietly without you knowing about it. Once you know what's causing it, it's usually fixable.
If you're curious about your rating or thinking about improvements before selling or renting, I can talk you through what's likely to make the biggest difference for your property. Book an assessment or call me on 07718 285708 and I'll give you a straight answer.
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