Over half of all English homes now hold an Energy Performance Certificate rating of C or better — that’s 56% of dwellings in 2024, up from just 26% a decade earlier. If you’re shopping for an apartment, that figure matters more than you might think. It tells you the market is shifting fast, and the flat you buy today could feel very different on your energy bills than one bought even five years ago.
I’ve been writing about UK property long enough to notice a pattern. Buyers spend hours comparing square footage, lease lengths, and service charges, but they rarely ask for the EPC before the viewing. By the time they do, they’ve already fallen for the bay window or the high ceilings. That’s a mistake that costs hundreds of pounds a year. The English Housing Survey data shows the average SAP rating — the government’s measure of energy efficiency — has climbed from 45 points in 1996 to 68 points in 2024. That’s real progress, but it also means older flats that haven’t been upgraded are falling further behind. Here’s what you actually need to know.
If you’re looking at a flat with an EPC below C, you need to know what you’re signing up for. A Band D property costs roughly £1,500 to £2,000 a year in energy, while a Band C home runs closer to £1,100 to £1,500. That gap adds up fast. And if you’re buying in the private rented sector, remember that landlords in England already face minimum standards of EPC E, with a proposed target of C by 2030. That same pressure is coming for owner-occupied homes eventually. I’d want to know where my potential flat sits before I made an offer. You can also check broader buying strategies for uncertain times to see how energy costs fit into the bigger picture.
What an EPC rating actually tells you about a flat
The most important thing to understand about an Energy Performance Certificate is that it’s not a vague suggestion — it’s a scored assessment. The SAP score runs from 1 to 100, and that number maps directly onto the letter bands you see on the certificate. A score of 69 to 80 gets you a Band C. Below 55 and you’re in Band E territory, which means annual energy costs of £2,000 to £2,800. That’s real money.
What I tend to notice is that buyers assume a flat in a modern block will automatically score well. That’s often true — new-build apartments are designed to meet current standards. But conversions of older buildings can be a mixed bag. A converted Victorian flat might have solid brick walls that are hard to insulate, single-glazed sash windows, and a communal heating system that’s past its best. The EPC will flag all of that. My first move would be to check the EPC register before I even booked a viewing. It’s free, it’s public, and it saves you wasting a Saturday afternoon on a flat that’s going to cost you a fortune to heat. For more on what to look for in a flat’s physical condition, water pressure is another hidden issue that can catch buyers out.
Why energy efficiency matters more than you think
This isn’t just about being warm in winter. The financial implications run deeper than your monthly bill. Let me give you a scenario. You’re looking at two similar one-bedroom flats in the same city. Flat A has an EPC of C, with estimated annual energy costs of £1,300. Flat B is rated E, with costs around £2,400. Over a five-year mortgage fix, that’s a difference of £5,500 — money that could have gone towards your deposit or your next holiday.
The English Housing Survey shows that social rented dwellings — which include many purpose-built flats — are the most energy-efficient sector, with average SAP ratings of 71 for local authority homes and 72 for housing association properties. That’s partly because flats have less exposed surface area through which heat escapes. But private rented flats lag behind, with only 48% reaching Band C compared to 69% of social rented homes. If you’re buying a flat that’s currently rented out, the current tenant’s bills might already be telling you something.
I’d also think about resale value. The proportion of homes in bands A to C has more than doubled in a decade. Buyers in 2030 will expect a C as standard. A flat stuck at E or F will be harder to sell, and you’ll be competing against a market that’s moved on. If you’re weighing up whether a flat is the right choice for you at all, the flat-versus-house debate covers the trade-offs in more detail.
Where buyers get tripped up on energy efficiency
Ignoring the EPC until after the offer
This is the most common mistake I see. Buyers fall in love with a flat’s layout, location, or natural light, and only check the EPC when the solicitor sends it over. By then, you’re emotionally invested. The fix is simple: look up the EPC online before you view. If it’s Band E or below, ask the estate agent what improvements have been made. If the answer is vague, factor the cost of upgrades into your budget. A cavity wall fill for a flat might cost £400 to £800 if you’re eligible for the Great British Insulation Scheme, but solid-wall insulation is far more expensive.
Assuming a modern build means a good rating
Most new-build flats score well, but not all. Some developments from the early 2000s were built to lower standards than today’s Building Regulations. Check the actual SAP score, not just the letter. A Band C at the bottom of the range (score 69) is a different proposition from a Band C at the top (score 80). The difference in annual energy cost can be several hundred pounds.
Overlooking the heating system type
Flats often have communal heating systems, electric storage heaters, or heat pumps rather than a gas boiler. Each has different running costs and maintenance requirements. The EPC will tell you the heating type, but it won’t tell you how old the system is or whether the communal boiler is due for replacement. Ask the management company for the service history. If the system is nearing the end of its life, you could be facing a special assessment for a replacement. That’s a cost that won’t show up on the EPC.
Missing the insulation picture
Around 25% of heat is lost through an uninsulated roof, and uncontrolled air leakage accounts for roughly 20% of heat loss in a typical home. In a flat, the roof might be above the top-floor unit only, but heat can also escape through external walls and windows. Check whether the flat has loft insulation (if applicable), cavity wall insulation, and double or triple glazing. If the EPC says “assumed” rather than “measured” for any of these, treat it as a red flag.
→ Scroll right to see all columns
| EPC Band | SAP Score | Typical Annual Energy Cost | What It Means |
|---|---|---|---|
| A | 92–100 | £500–£800 | New-build standard; very well insulated |
| B | 81–91 | £800–£1,100 | High performance; modern heating |
| C | 69–80 | £1,100–£1,500 | Average new-build or well-improved older home |
| D | 55–68 | £1,500–£2,000 | UK average; most homes fall here |
| E | 39–54 | £2,000–£2,800 | Below average; significant improvements possible |
| F | 21–38 | £2,800–£4,000 | Poor; likely uninsulated, old heating |
| G | 1–20 | £4,000+ | Very poor; solid walls, no insulation |
How to check and improve a flat’s energy efficiency before you buy
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Pull the EPC before you view
Go to the government’s EPC register website. Enter the property postcode. You’ll see the current certificate, the recommended improvements, and the estimated cost of each upgrade. This takes five minutes and tells you whether the flat is worth your time. If the certificate is more than ten years old, it needs renewing before the sale can complete — but you can still use it as a starting point. Pay attention to the “potential rating” section. If the flat could reach Band B with relatively cheap measures like loft insulation and draught-proofing, that’s a good sign. If the recommended improvements are all expensive structural work, think twice.
Ask about recent upgrades
The EPC might be based on assumptions that are out of date. Ask the seller or estate agent whether any improvements have been made since the certificate was issued. New double glazing, loft insulation, or a boiler replacement should all be reflected in a new EPC. If they haven’t bothered to update it, that tells you something about how the property has been maintained. A carbon monoxide alarm is a sensible addition to any flat, especially one with an older heating system, but it won’t fix efficiency — it’s about safety while you plan upgrades.
Check the heating system type and age
If the flat has a gas boiler, find out the make, model, and installation date. A boiler over 15 years old is likely operating at around 80% efficiency. Modern condensing boilers can reach over 90%. If the flat uses electric storage heaters, check whether they’re the modern slimline type or the old heavy bricks. The former are more controllable and cheaper to run. For communal heating, ask the management company for the system’s efficiency data and the planned replacement schedule. If the flat has a heat pump, ask for the heat pump’s efficiency coefficient and service records.
Look at the fabric of the building
You can’t change the fact that a flat has solid brick walls without expensive internal or external insulation. But you can check whether the windows are double-glazed, whether the loft (if you have one) is insulated to at least 270mm, and whether there are obvious draughts around doors and windows. A draught-proofing kit costs around £20 and can save £125–£175 a year on heating bills according to the Energy Saving Trust. That’s one of the quickest returns you’ll ever get on a home improvement.
Factor upgrade costs into your offer
If the flat needs work, don’t just accept it — negotiate. A new boiler costs £1,500–£3,000. Cavity wall insulation runs £400–£800. Loft insulation is £300–£500. If the EPC recommends £5,000 of work to reach Band C, that’s a legitimate reason to reduce your offer by a similar amount. The seller either does the work before completion or accepts a lower price. Either way, you win. For a deeper look at how service charges and other flat-specific costs can change over time, understanding strata fee increases is essential reading.
Future-proof your purchase
The government’s target is for all homes to reach EPC C by 2035, and the private rented sector faces a 2030 deadline. Even if you’re buying to live in, these targets will affect the market. A flat that’s already at Band C or above will hold its value better than one that needs significant work. If you’re buying a flat rated D or below, have a plan for how you’ll improve it within the next five years. That might mean budgeting for insulation, a new heating system, or solar panels if the flat has roof access. The Electrification of Heat project found that simply lowering your boiler flow temperature to 55°C saves an average of £112 per year with no loss of comfort — a free improvement you can make the day you move in.
Can I get a mortgage on a flat with a low EPC rating? ▾
Does a higher EPC rating increase the property value? ▾
What if the flat has a communal heating system? ▾
Can I improve the EPC of a leasehold flat? ▾
How long does an EPC last? ▾
Are there grants available for energy efficiency improvements? ▾
The bottom line is simple: energy efficiency isn’t a nice-to-have when you’re buying a flat — it’s a financial decision that affects your monthly budget, your resale value, and your legal obligations down the line. Check the EPC before you view, ask the right questions about the heating system and insulation, and factor the cost of any upgrades into your offer. A flat that’s already at Band C or above saves you money from day one and protects you against future regulatory changes. If this was useful, you might also want to read first-time buyer mortgages for UK apartments.
Sources and Further Reading
Apartment buying vs renting in the UK — A detailed comparison of the long-term financial case for buying versus renting a flat, including energy cost considerations.
English Housing Survey 2024 to 2025: energy efficiency. Ministry of Housing, Communities and Local Government, 2025.
The Complete Guide to Making Your UK Home Energy Efficient. UK Home Energy, 2025.
