Fact 38. EPC Rating Dropped After a New Assessment? Why It Happens and How to Fix It
Quick answer
A new EPC can score lower than the one before it because the assessor can only credit what they can see or prove on the day, and once the new certificate is registered it replaces the old one, even if the old one was better and still in date.
Three things usually cause the drop:
Something was out of sight. A blocked loft hatch, a locked cupboard or an unreachable boiler means the software falls back on assumptions based on the age of the building.
Something couldn’t be proved. Insulation fitted years ago, with no invoice, photo or sign-off, generally can’t be counted. The assessor can’t take the owner’s word for it.
The inputs or calculations differ. Heating, fuel and wall details are recorded afresh each time, and the calculation assumptions have been revised over the years, so two assessments of an unchanged home can disagree.
If you have just received a lower rating, don’t order another straight away. Find what the new certificate marks as “assumed”, gather evidence for it, and ask the assessor to correct it. If you are mid-sale or mid-tenancy, tell your solicitor or agent the same day, because buyers, lenders and councils act on the newest certificate.
The rule most owners miss: the newest EPC replaces the old one
An EPC lasts ten years from the date it goes on the register, but the guidance councils publish for England and Wales says that period ends early if a newer EPC is produced and registered. The latest registered certificate is the valid one, whatever the previous one said.
In practice that means:
You can’t keep a better certificate in reserve. The register holds every certificate for a property, but the most recent one is the one that counts.
Ordering a new EPC “to be safe” is not risk-free. If it comes out lower than the one you already hold, you have swapped a good certificate for a worse one.
A lower rating has knock-on effects. For a sale, buyers and lenders see the new figure. For a let property, a rating below the minimum standard can leave the landlord unable to let lawfully.
Check before you commission. Search your address on the government’s Find an energy certificate service. If you hold an in-date certificate and nothing significant has changed, you may not need a new one at all.
When a property is marketed without a valid EPC, sellers must make every reasonable effort to get one within seven days, with a further 21 days allowed. After 28 days, the local authority can issue a penalty of up to £200 for a dwelling.
Why a re-assessment can score lower than the first
An assessor is carrying out a survey, not taking a statement. If a feature can’t be seen or evidenced, the software fills the gap with a default based on the age of the building, and those defaults are rarely generous.
Common problems and what happens:
Loft hatch blocked, locked, painted shut or unsafe to climb into → The certificate assumes loft insulation based on the age of the building, often none. What helps: clear the hatch, provide a safe ladder and light.
Insulation fitted years ago with no paperwork → Not counted without supporting evidence such as receipts. What helps: invoices, installer certificates, dated photos.
Cavity or underfloor insulation that can’t be seen (for example behind render or after repointing) → “As built” values for the age of the property, marked “(assumed)”. What helps: guarantee or installer paperwork.
Fuel or heating recorded wrongly → A large swing in score, because running cost drives the rating. What helps: check the features table on the certificate and ask for a correction.
Two details catch people out.
Assessors are not required to take unnecessary risks. If the loft has no safe access, they record an assumption rather than climbing in. Some will photograph an area they couldn’t inspect, such as a fully boarded loft, but photographs of the hatch are not evidence of what lies behind it.
An old certificate can be wrong in your favour. One assessor reported inspecting a home with filled cavities, loft insulation and double glazing that scored F (28) because it was not on mains gas, and then found the previous certificate, D (55), had wrongly recorded mains gas. A fresh assessment can correct an old error in the direction you don’t want.
It can also go the other way. Some landlord guidance notes that very old certificates may understate a property’s true rating, so a re-assessment is a gamble in both directions. That is why it pays to find out what is on the existing certificate first.
What evidence an assessor will accept
There is no single approved list, and assessors differ, so ask before the visit. One landlord reported an assessor who refused a letter from building control; another found an assessor who accepted architect’s drawings plus the completion sign-off, and the clincher was a photograph from the build showing a stack of insulation boards in the corner.
What tends to help:
Loft insulation: the best evidence is the loft itself. Clear the hatch, provide a safe ladder and light, and let the assessor measure the depth.
Hidden insulation (walls, floors, rafters): photographs taken while the work was open, with a tape measure in shot; itemised invoices naming the product and thickness; an installer’s report or guarantee.
Extensions and conversions: the Building Regulations completion certificate, plus the drawings or specification that state the insulation.
Heating: the boiler’s make and model, and the installer’s commissioning paperwork.
Don’t rely on the certificate from the work alone. A landlord who refurbished a house to a C rating nearly ten years earlier was told at renewal that it would drop to a D because the insulation could no longer be seen. She held a building regulations certificate, but it gave no detail of the work. The lesson drawn from her story is to keep a detailed installer report, dated photos and receipted invoices from the day the work is done, because once the walls and floors are closed up, those records are the only proof.
Never agree to open up finishes without checking with the assessor what they would accept first. And remember the assessor’s survey is visual and non-destructive, so they cannot verify what they cannot see.
Case study: the £85 certificate that nearly cost a Somerset landlord £17,500
Illustrative scenario. The people and property are fictional, but each step follows the rules described on this page.
The cottage and the plan. Helen Dyer, 61, owns a two-bedroom Hamstone cottage in Norton sub Hamdon, built around 1880, with 450mm solid stone walls, a slate roof and a condensing combi boiler fitted in 2016. She has let it since 2019 to Ben and Chloe Pitt and their baby daughter. A Taunton investor with six rental homes has offered £242,500 and wants the Pitts to stay on. Helen needs the money to buy a flat in Bath near her own daughter, and the Bath sellers want to exchange within five weeks.
Her certificate was already fine. The cottage holds a 2018 EPC rated E (47), valid until 2028. It recorded the 150mm of loft insulation she had laid that year, paid for in cash with no invoice and no photographs.
The “routine” step. The agent in Martock suggests a fresh EPC for £85, so that the buyer’s solicitor has “something current”. It isn’t needed, because the 2018 certificate is in date, but Helen agrees.
The visit. The loft hatch sits in the ceiling of the back bedroom, above a wardrobe, and the Pitts’ daughter naps in that room. Ben is at work. Chloe, who was never told why access mattered, asks the assessor not to disturb the cot. The assessor records that the loft could not be accessed and photographs the shut hatch. For a house of that age, the software assumes the roof has no insulation. The certificate is lodged that evening: F (36).
What happened next:
Day 0: Assessment. Loft not accessed. Insulation assumed absent.
Day 1: New EPC lodged: F (36). It replaces the 2018 E (47) as the valid certificate.
Day 4: The buyer’s solicitor sees the F. The buyer’s lender says it won’t lend on a home that can’t lawfully be let. The cottage is tenanted and now below the minimum standard of E.
Day 5: The buyer asks for £17,500 off, to £225,000, “to cover works and risk”. Helen’s Bath purchase is now at risk.
Day 7: Helen reads the certificate’s features table and finds the roof marked “assumed”. The problem is evidence, not insulation.
Day 9: Wardrobe moved, hatch cleared. An installer measures 150mm, photographs it, then tops it up to 270mm for £850. The first proof the loft has ever had.
Day 11: A second assessor reassesses for £85: E (51). Lodged, replacing the F.
Day 13: The lender re-approves. Price agreed at £240,000. Exchange follows; completion about five weeks late.
Why it mattered three times over:
The old certificate stopped counting. The E (47) was valid until 2028 and was enough to sell. Ordering the new one replaced it.
Helen was briefly in breach. From the day the F was lodged until the E replaced it, she was letting a home below the minimum standard, with exposure to a penalty of up to £5,000 from Somerset Council. She wrote to the council explaining the cause and the fix, and no penalty followed, though that was never guaranteed.
The buyer’s lender reacted to the register, not to the roof. Nobody had visited the loft except the person who couldn’t get in.
The options Helen weighed:
Challenge the F. The assessor was sympathetic but could not change an entry without evidence, and Helen had none. Her solicitor asked whether the 150mm on the 2018 certificate would do. The assessor wanted to see it for themselves.
Register an exemption. Not realistic. The recommended loft top-up cost around £850, far below the £3,500 cost cap, so there was no case that improvements were too expensive.
Accept the cut or find another buyer. Any new buyer would see the same F on the register.
Open the loft and prove it. The only route that fixed the cause, and the one she took.
The result
Most of the 15-point recovery came simply from the loft being recorded as it really was. The top-up and the better-documented boiler added a few more points.
Costs:
First EPC (superseded): £85
Loft top-up with photographs: £850
Second EPC: £85
Price reduction finally agreed: £2,500
Total real cost: £3,520
Price reduction first demanded: £17,500
The sting in the tail. The accurate E (51) answered the immediate problem and raised another. The buyer’s adviser noticed that the government has confirmed it intends to raise the minimum for rented homes to band C (69 or more) from 1 October 2030. A solid-stone cottage at 51 has a long way to go, and a builder’s rough figure for the insulation needed sat close to the proposed £10,000 spending cap. The £2,500 reduction covered the delay and that question together. An accurate certificate cost Helen money, but it showed both sides the real position, which a wrongly low F would have obscured.
What it shows. An in-date certificate is not a reason to order another. The cheapest fix was available all along: a clear loft hatch and a briefed tenant. And what cost Helen most was not the missing insulation but the missing paperwork.
Before you order a new EPC: a checklist
Look up what’s already registered. Search your address on the government’s Find an energy certificate service. A certificate shows two dates, the assessment date and the certificate date, and the ten years run from the certificate date. If yours is in date and nothing significant has changed, you may not need a new one.
Read the features table on the existing certificate. Entries marked “(assumed)” show what the last assessor could not evidence. These are the entries most likely to move in a new assessment, in either direction.
Ask why a new one is wanted. If an agent or solicitor suggests refreshing it “to be safe”, ask what problem it solves and whether the in-date certificate would do.
Gather evidence for any work done. Invoices that state the product and thickness, installer certificates, Building Regulations sign-offs and dated photographs.
Prepare access. Clear the loft hatch and provide a safe ladder and light. Unlock the boiler cupboard, meter and hot water cylinder. If the property is tenanted or occupied, tell the occupiers in writing what the assessor needs to see, and why.
Do the cheap jobs first. Fit LED bulbs, deal with obvious draughts and top up loft insulation if recommended. Landlord guidance suggests completing the recommendations on the old certificate before commissioning a new one.
Ask the assessor before booking. What evidence will you accept? Will you go into the loft, and how do you treat a boarded one? Is the certificate lodged immediately after the visit? Once it is registered it replaces the old one.
Plan for a bad result. Know who you would call, keep the assessor’s contact details, and budget for a reassessment fee.
If the new rating is worse than the old one
You can’t simply revert to the earlier certificate, because the newest registered one is the valid one. The route is to correct the new one or replace it with a better-evidenced one.
Compare the two certificates. Check the features table for what changed: roof, walls, floor, heating, fuel and lighting. Look for the “(assumed)” entries first.
Write to the assessor with evidence. Their contact details are on the certificate, and a careful assessor will hold site notes and photographs from the visit. Send photos, invoices and certificates, and ask them to correct the entry or reassess.
Escalate if they won’t engage. If you believe the certificate is wrong, complain through the assessor’s accreditation scheme, which the certificate identifies.
Fix the cause, then reassess. If the cause was access, clear it. If it was proof, produce it. If something is genuinely missing, a cheap improvement may be quicker than an argument.
If you let the property, check it against the minimum standard. In England and Wales that is band E today. If the new rating is below it, take advice before granting any new tenancy, and ask about exemptions and the council’s view.
If you are selling, tell your solicitor and agent the same day. Explain what happened, share your evidence and give the buyer a timetable for the corrected certificate. Buyers and lenders react far worse to a surprise they find on the register than to a problem you have already flagged and are fixing.
This is general information, not legal advice.