The cheapest ways to improve an EPC rating
A SAP point costs anywhere from about £20 to nearly £2,000 depending on how you buy it. Cylinder insulation, loft insulation and low energy lighting are the cheapest points on the board.
Last reviewed 24/09/2026
Every measure on an EPC recommendation report has a price and a number of SAP points attached to it. Divide one by the other and the list reorders itself completely — and that reordered list is the cheapest way to move a band.
The spread is enormous. Insulating a hot water cylinder costs about £20 a point. Replacing windows costs over £1,600 a point. Both appear on the same report, in the same typeface, as though they were comparable.
Cheapest first
| Measure | SAP points | Installed cost | Cost per point |
|---|---|---|---|
| Hot water cylinder insulation | +2 | £20–£60 | £20 |
| Loft insulation to 270 mm | +4 | £100–£350 | £56 |
| Low energy lighting throughout | +1 | £25–£90 | £58 |
| Cavity wall insulation | +9 | £600–£1,800 | £133 |
| Heating controls and TRVs | +3 | £350–£900 | £208 |
| Condensing gas boiler | +8 | £2,200–£3,600 | £363 |
| Solar PV, 3 kWp | +11 | £5,000–£8,000 | £591 |
| Internal solid wall insulation | +12 | £4,000–£14,000 | £750 |
| Double glazing throughout | +3 | £3,300–£6,500 | £1,633 |
| Air source heat pump | +6 | £9,000–£14,000 | £1,917 |
Cost per point uses the middle of each indicative range, for an average sized property in England & Wales.
How far £1,000 gets you
On a typical band D property with an uninsulated cavity: cylinder insulation, loft insulation to 270 mm, low energy lamps and cavity wall insulation come to roughly £745 at the bottom of the ranges and £2,300 at the top, and are worth about 16 SAP points.
Sixteen points is more than the gap between most band D scores and band C. That is the whole argument for doing the cheap work first: for a four figure sum at the low end, a majority of band D properties become band C properties.
What to avoid when money is tight
Double glazing is the classic trap. It earns roughly 3 points for £3,300 to £6,500, because the calculation already assumes reasonable windows in many properties. Replace windows because they are rotten, draughty or unsafe — not to move a band.
A heat pump is the most expensive way to buy SAP points in the current methodology, at around £1,900 a point, because SAP prices electricity well above gas. On a property running electric storage heaters the picture is completely different, and the gain is large. On a property with a working condensing boiler it is not a band-moving measure.
Solar PV sits in between. It is expensive per point but it does not care about the fabric, which makes it one of the few options left on a home that is already well insulated.
Free and nearly free
- Fit the low energy lamps you already own into every fitting before the assessor arrives.
- Find the paperwork for insulation already installed, so it is recorded rather than assumed absent.
- Top loft insulation up yourself — the material is the bulk of the quoted price, and it is a morning’s work.
- Turn the hot water cylinder thermostat down to 60°C and make sure the jacket is fitted properly.
- Make the loft hatch and the meter cupboard accessible so nothing has to be assumed.
Help with the cost
Households on qualifying means tested benefits with a property in bands D to G may have the work funded under ECO4, which is paid for by energy suppliers rather than by a government department. Councils can also refer low income households that are not on benefits, under flexible eligibility.
ECO4 runs to 31 December 2026, and there is no ECO5 — the Warm Homes Plan takes over from 2027. If you might qualify, it is worth checking before paying for anything.
One thing to remember
None of this changes the certificate until a new assessment is lodged. If you spend £745 on the cheap measures and never re-assess, the register still shows band D, and for a rented property that means you are still non-compliant in 2030. Budget the £45 to £120 for the new EPC as part of the job.