EPC Ratings Explained: What They Mean for Heat Pumps and Grants
TLDR: Energy Performance Certificates (EPCs) rate homes from A (most efficient) to G (least). The £7,500 Boiler Upgrade Scheme grant requires EPC D or better. Most UK homes are rated D or E. Improving one band often requires simple, affordable measures: loft insulation (£300-£600), LED lighting (£100-£200), or draught-proofing (£100-£300). EPCs cost £60-£100 and are valid for 10 years.
If you're considering a heat pump for your home, there's one document that will determine whether you can access the £7,500 government grant: your Energy Performance Certificate. The EPC is essentially a report card for your home's energy efficiency, and it's become the gatekeeper to the UK's most generous renewable heating incentive.
Understanding EPCs isn't just about ticking a box for grant eligibility. Your EPC rating directly affects how well a heat pump will work in your home, how much it will cost to run, and ultimately whether you'll be satisfied with your investment. A poorly insulated home (low EPC) makes heat pumps work harder, cost more to run, and deliver less comfortable results.
This guide explains everything you need to know: what the ratings mean, how to improve yours, what assessors look for, and real stories from homeowners who've navigated the system. Whether you're sitting comfortably at D or nervously at F, there's a path forward.
The EPC Scale: Understanding the Ratings
EPC ratings use a points system from 1 to 100, mapped onto letter grades from G (worst) to A (best). The rating reflects your home's energy efficiency—how much energy it uses per square metre to heat, light, and power.
| Rating | Score | Description | % of UK Homes |
|---|---|---|---|
| A | 92-100 | Highly efficient (new Passivhaus-standard builds) | 1% |
| B | 81-91 | Very efficient (modern well-insulated homes) | 3% |
| C | 69-80 | Efficient (good insulation, modern heating) | 16% |
| D | 55-68 | Average (minimum for BUS grant) | 37% |
| E | 39-54 | Below average (common in older homes) | 29% |
| F | 21-38 | Poor (needs significant improvement) | 10% |
| G | 1-20 | Very poor (needs major work) | 4% |
The average UK home sits at EPC D, scoring around 60 points. About 43% of homes are E, F, or G—meaning they don't currently qualify for the BUS heat pump grant without improvements.
Why EPC Matters for Heat Pumps
Your EPC rating affects heat pumps in two critical ways: grant eligibility and system performance.
Grant Eligibility: The D Threshold
The Boiler Upgrade Scheme (BUS) provides £7,500 toward air source heat pump installation—a substantial chunk of the typical £10,000-£15,000 total cost. But to qualify, your home must have an EPC rating of D or better.
There is some flexibility. If your current EPC is E but you're planning improvements that will reach D, some installers can work with the scheme to demonstrate a clear upgrade path. This typically requires committing to insulation or other improvements as part of the heat pump project.
System Performance: Why Efficiency Matters
Beyond grants, your EPC reflects something fundamental: how leaky your home is. A poorly insulated home loses heat rapidly, which means:
- Larger heat pump required: More heat loss means you need a bigger, more expensive heat pump to maintain comfortable temperatures.
- Higher running costs: The heat pump works harder and longer, consuming more electricity.
- Reduced comfort: Draughty rooms and cold spots persist even with heating on.
- Lower efficiency: Heat pumps running at high output to compensate for poor insulation operate at lower COP (coefficient of performance).
Put simply: improving your EPC before installing a heat pump reduces costs upfront (smaller pump) and ongoing (lower bills).
Real Homeowner Experiences with EPC
Rachel, Cambridge (1960s semi-detached): "Our EPC was E when we first looked into heat pumps. The assessor's report showed we were losing huge amounts of heat through the loft—only 100mm of ancient insulation. We paid £480 to top up to 300mm, replaced the remaining halogen bulbs with LEDs for £120, and had the cavity walls checked. They'd been filled in the 1980s but had slumped in places, so we got them re-filled under ECO4 for free because my husband receives PIP. A new EPC came back at D (62 points). Total cost to us was £600, and we now qualify for the £7,500 BUS grant. The heat pump installer said our improved insulation also meant we could use a 9 kW pump instead of the 11 kW we'd have needed before—saving about £1,500 on equipment."
David and Maria, Bristol (Victorian terrace): "Our EPC was a scary F (34 points). Solid walls, original sash windows, very little insulation anywhere. The assessor's recommendations looked daunting: external wall insulation, new windows, the lot. We thought the heat pump dream was over. But our installer suggested a phased approach. First, we did internal wall insulation on the coldest rooms (£8,500 for about 60 square metres), secondary glazing rather than full window replacement (£3,200), and comprehensive draught-proofing (£650). That got us to D (58 points). We qualified for ECO4 funding for some of the wall insulation because Maria has a health condition that qualifies under Flex. The heat pump went in last month, and we're genuinely warm for the first time in 15 years of living here."
Tom, Sheffield (1970s detached): "I thought our house was reasonably efficient—we'd done the loft years ago, had double glazing, all that. But the EPC came back at E (52 points). The surprise was that our old gas boiler was dragging the rating down significantly. The assessor explained that the EPC calculation assumes standard usage patterns, and our 25-year-old 60% efficient boiler was killing our score. When we installed the heat pump, our EPC jumped to C (74 points) on the post-installation reassessment. The heat pump itself added about 22 points."
Angela, Norwich (1930s bungalow): "Getting from F to D felt impossible at first. Our bungalow had solid walls, concrete floors with no insulation, and a flat roof extension that was basically a freezer. We tackled it in stages over 18 months. First, the loft and flat roof (£2,800). Then internal wall insulation in the main rooms (£7,200). Underfloor insulation when we replaced the kitchen floor anyway (£1,600). Each improvement bumped our EPC up: F to E after the loft, E to low D after the walls, and comfortably D after the floor. By the time we were ready for the heat pump, our home actually held heat properly. The pump runs at much lower temperatures than it would have before, which the installer said would save us 20-25% on running costs compared to our original state."
Common Improvements and Their EPC Impact
Different improvements add different numbers of EPC points. The impact varies depending on your starting point and home type, but here are typical ranges:
| Improvement | Typical EPC Points | Typical Cost | Notes |
|---|---|---|---|
| Loft insulation (to 270mm+) | 8-15 points | £300-£600 | Biggest bang for buck for most homes |
| Cavity wall insulation | 10-20 points | £500-£1,500 | Only if you have unfilled cavities |
| Solid wall insulation (internal) | 15-25 points | £6,000-£15,000 | Expensive but transformative |
| Solid wall insulation (external) | 15-25 points | £10,000-£25,000 | Changes appearance, needs planning |
| LED lighting throughout | 3-8 points | £100-£200 | Quick, cheap improvement |
| Draught-proofing | 2-5 points | £100-£400 | DIY-able, immediate comfort benefit |
| Hot water cylinder jacket | 2-4 points | £20-£50 | If your cylinder isn't already insulated |
| Double glazing (replacing single) | 10-18 points | £5,000-£15,000 | Big impact if you have single glazing |
| Floor insulation | 3-8 points | £1,000-£3,000 | Best done during renovation |
| Heating controls upgrade | 2-5 points | £150-£400 | Smart thermostat, TRVs on all radiators |
The Quick Wins
If you're just a few points short of D, focus on cheap, quick improvements:
- Loft insulation top-up: If you have less than 270mm, topping up is the single most cost-effective improvement.
- LED bulbs: Replace any remaining incandescent or halogen bulbs. The EPC calculation includes lighting efficiency.
- Draught-proofing: Seal gaps around windows, doors, letterboxes, and loft hatches. DIY kits cost under £100.
- Hot water cylinder jacket: If your tank isn't insulated, a £25 jacket adds easy points.
- Heating controls: Adding TRVs (thermostatic radiator valves) and a programmer can nudge your score up.
These measures combined might cost £500-£1,000 and could add 10-20 points—enough to jump from E to D in many cases.
Getting an EPC: The Assessment Process
EPCs must be produced by accredited Domestic Energy Assessors. You can find assessors through the government's EPC register at find-energy-certificate.service.gov.uk or through comparison sites.
What to Expect
- Cost: Typically £60-£100 for a standard home. Larger or more complex properties may cost more.
- Duration: 45-90 minutes on-site, depending on home size and complexity.
- Access: The assessor needs to see the loft, boiler, all rooms, windows, and external walls.
- Validity: EPCs are valid for 10 years, but you can get a new one earlier if you've made improvements.
What the Assessor Examines
Assessors look at specific elements and assign standard values:
- Walls: Construction type (solid, cavity, timber frame) and insulation status.
- Roof/loft: Insulation depth and type.
- Windows: Single, double, or triple glazed; age and type.
- Floors: Construction and insulation.
- Heating system: Boiler type, age, and efficiency; controls and programmer.
- Hot water: How water is heated, cylinder insulation.
- Lighting: Proportion of low-energy bulbs.
- Renewable energy: Solar panels, heat pumps, etc.
Preparing for an Assessment
To get an accurate (and hopefully better) rating:
- Find evidence of insulation: Cavity wall guarantee certificates, loft insulation receipts, building control completion certificates.
- Make the loft accessible: Clear boxes away from the hatch so the assessor can measure insulation depth.
- Know your boiler details: Have the model number visible (often inside the front panel).
- Replace any obvious old bulbs: Swap halogens for LEDs before the assessment—it only takes a few minutes.
- Provide window details if available: FENSA certificates or receipts showing when double glazing was installed.
Without evidence, assessors must assume the worst. A cavity wall assumed unfilled scores lower than one with documented insulation.
ECO4 and Other Support for Low-EPC Homes
If your EPC is E, F, or G, you may qualify for the Energy Company Obligation (ECO4) scheme, which provides free or heavily subsidised insulation.
Who Qualifies for ECO4?
- Households receiving means-tested benefits (Universal Credit, Pension Credit, Child Tax Credit, etc.)
- Households with a member receiving disability benefits (PIP, DLA, Attendance Allowance)
- ECO Flex referrals from your local council (targets low-income or health-vulnerable households)
What ECO4 Covers
- Loft insulation (often fully funded)
- Cavity wall insulation (often fully funded)
- Solid wall insulation (often partially funded, sometimes fully)
- Underfloor insulation
- Some heating system upgrades
If you're on benefits and have a low EPC, contact your energy supplier or local council to check eligibility. Companies like British Gas, EDF, and Octopus Energy all have ECO4 programmes.
Q&A: EPC Ratings and Heat Pumps
Q: My EPC is E. How do I reach D?
A: Usually straightforward with the right improvements. Loft insulation top-up, LED lighting throughout, and draught-proofing often bridge E to D for under £1,000. Check the assessor's recommendations on your current EPC—they're listed in order of cost-effectiveness.
Q: Does a heat pump improve my EPC?
A: Yes, significantly—typically 10-25 points. Replacing a gas or oil boiler with a heat pump dramatically improves the heating section of the EPC. However, you need D before installation to qualify for the BUS grant. Some homeowners get a post-installation EPC to document the improvement for resale purposes.
Q: What if I'm F or G rated?
A: Major improvements are needed, but it's not impossible. Focus on insulation first: loft, walls, floors. Check ECO4 eligibility—if you qualify, you can get substantial work done for free or low cost. Consider a phased approach over 12-24 months, tackling one major element at a time. Many installers can advise on the most cost-effective path to D.
Q: Can I get the BUS grant if I'm at E but planning to improve?
A: Sometimes. Some installers work with the scheme to accommodate homes that will reach D as part of the overall project. This might mean committing to insulation work before or alongside the heat pump installation. Discuss this with potential installers early in the process.
Q: How long does it take to get a new EPC after improvements?
A: You can book a new assessment as soon as improvements are complete. The assessor visits, re-measures, and issues a new certificate—usually within a week. The new EPC replaces the old one and is valid for 10 years.
Q: My EPC seems wrong—what can I do?
A: If you believe the assessor made errors (e.g., marked your walls as solid when they're insulated cavity), contact the assessor first. They can correct factual errors. If you have new evidence (found the cavity wall insulation certificate you couldn't find before), get a new assessment—it's worth the £60-£100 if it bumps you up a band.
Q: Do I need an EPC to sell or rent my home?
A: Yes. EPCs have been mandatory for property sales and rentals since 2008. For rentals, the minimum standard is currently E (with some exemptions), but this is expected to rise to C by 2030 for new tenancies.
The Bottom Line
Your EPC rating is more than a bureaucratic hurdle—it's a genuine measure of how well your home retains heat. Improving your EPC doesn't just unlock the £7,500 BUS grant; it makes your heat pump work better, run cheaper, and keep you more comfortable.
For most E-rated homes, reaching D is achievable for £500-£1,500 in targeted improvements. The combination of grant eligibility and better heat pump performance makes this investment worthwhile several times over.
If you're starting from F or G, the path is longer but not impossible. ECO4 grants can cover significant costs for eligible households. Even without grants, the fabric improvements pay back through lower heating bills and higher property value.
The first step is getting an accurate EPC. Find an assessor, gather your insulation evidence, and see where you stand. Many homeowners are pleasantly surprised to find they're closer to D than expected—or that the improvements needed are simpler and cheaper than feared.
Your home's energy efficiency journey starts with understanding where you are. The EPC gives you that starting point, and the path to D—and a heat pump—may be shorter than you think.