How many EPC points do solar panels add? What decides your number

There is no fixed number of EPC points per panel. Assessor guidance and installer data point to a range of about 6 to 15 SAP points for a typical 4kWp roof array, with most homes around 8 to 12. Six things decide where you land:

• Heating fuel. In a gas home, solar only offsets electricity. In an all-electric home it also offsets heating, so the same array usually scores higher.
• Array size and aspect. More kWp facing south means more modelled generation. East and west roofs still count, at lower output.
• Floor area. The score is worked out per square metre, so the same array lifts a small flat more than a large detached house.
• Modelled electricity demand. RdSAP estimates it from the home’s size, occupancy and heating. Higher demand means more of your generation is credited at the full electricity price.
• Overshading. Trees, chimneys and neighbouring buildings cut the modelled output.
• Your starting score. Points only change your letter near a band boundary.

How EPC scoring works

An EPC score measures running cost, not how green your home is. RdSAP estimates the energy needed to heat, light and run the home to a standard pattern, prices it, and divides by floor area. Cheaper to run means more points. The points map onto bands of uneven width:

Because the bands are uneven, the same array can change one certificate and barely register on the next. A home at 62 that gains 8 points crosses into C at 70. A home at 72 that gains 8 reaches 80 and is still C.

What solar changes inside RdSAP

RdSAP credits your array with a modelled annual generation and offsets it against the home’s modelled electricity demand. The estimated running cost falls, and the score rises. Four points explain most of the odd numbers you’ll see quoted:

1. Gas homes usually gain less. Electricity is a smaller part of a gas-heated home’s modelled bill, so offsetting it moves the cost less. Expect the lower half of the range.
2. All-electric homes usually gain more. The panels offset heating too. Double-digit gains are common, and high-demand homes occasionally go beyond 15.
3. Exported electricity is credited, at a lower value. Power used in the home is valued at the full electricity price. Power sold to the grid is valued at a lower export price.
4. Batteries and diverters now count. RdSAP 10 can record a PV battery, but only when solar is also present and only with evidence. Assessors need photo or written proof of the make, model and usable capacity.

Solar does not touch fabric. Wall, loft and window assumptions stay as assessed. It is a generation measure, and the software treats it that way.

Worked examples, band by band

These runs are illustrative and use typical uplift ranges. Only your assessor’s software can score your house.

Cost per point: solar is an expensive way to buy EPC points

Our 2026 solar cost guide puts a 4kWp system at £5,500 to £7,500. Set that against the usual alternatives and the cost per SAP point looks like this. Costs and gains are indicative, and your certificate’s recommendations page lists modelled gains for your own home.

Loft gains depend on what’s up there already. A thin top-up adds far fewer points than insulating an empty loft. Per point, panels usually cost several times more than loft insulation, so buy solar for its other returns.

Most 4kWp systems save £500 to £800 a year once you add export income. GOV.UK’s clean energy campaign puts average savings at over £500. On a 12p to 16p Smart Export Guarantee tariff, the roughly 2,000 kWh a typical 4kWp system exports earns £240 to £320 a year, and far less on old 3p to 5p tariffs. Our SEG league table shows who pays what. Residential solar is also 0% VAT until 31 March 2027, which our grants guide puts at £1,000 to £2,000 saved on a typical 4kW system. The rate reverts to 5% after that date.

Landlords: EPC C by 1 October 2030, and where solar fits

The government’s January 2026 response set one deadline. From 1 October 2030, all privately rented homes in England and Wales must meet the equivalent of EPC C on the reformed certificate. The proposed earlier deadline for new tenancies in 2028 was dropped. The rule still needs Parliamentary approval, so watch for the final regulations.

The standard is not a single score. A rented home must first meet a fabric performance target, then meet either a heating system target or a smart readiness target, at the landlord’s choice. Solar mostly serves the smart readiness route. Reports suggest reaching C on that metric will typically need panels and a smart meter, but the thresholds aren’t final. Insulation comes first either way.

Other confirmed details:

• Cost cap. £10,000 per property, or the lower of £10,000 and 10% of value for homes under £100,000. The government’s own estimate is an average spend near £5,400. A property that still falls short can register a 10-year exemption.
• Current rule until then. Band E is the minimum. Letting an F or G without a registered exemption is unlawful.
• Head start. A home that reaches C on today’s certificate before 1 October 2029 stays compliant until that EPC expires.
• Funding. ECO4 runs to 31 December 2026, and the Warm Homes: Local Grant covers eligible private homes in England rated D to G. You need to start below C to qualify, so see our 2026 grants guide for eligibility.
• Flats. An array usually only counts on a flat’s certificate if it feeds that flat’s own meter. Communal arrays serving shared areas don’t appear on individual EPCs.

The EPC reform delay: what changed in 2026

The government plans to replace the single A to G headline with four metrics built on the Home Energy Model: energy cost, fabric performance, heating system performance and smart readiness. The launch was due in October 2026. On 9 March 2026 the government moved it to the second half of 2027. At the time of writing I found no confirmed launch date. Scotland has confirmed a matching delay.

• Energy cost: your generation shows up here, much as it does today.
• Smart readiness: batteries, smart controls and generation are recognised here.
• Fabric performance: solar adds nothing. A leaky home stays a leaky home on this metric.

Existing certificates stay valid for their ten years. The delay does not move the October 2030 rental deadline, so plan around fabric first.

Does the band jump actually pay?

It can, mainly when you sell or let. A 2024 Swansea University and University of Birmingham study of about five million Zoopla listings, matched to Land Registry prices for 2012 to 2018, found homes advertising solar panels sold for 6.1% to 7.1% more. Two caveats apply. It is an average, and the study doesn’t isolate how much of the premium comes from the EPC. Other analyses land lower, with one industry and Cambridge study finding 0.9% to 2%. Our guide to what solar does to your sale price covers the spread.

For lettings, the band is a legal gate from 2030, so its value is binary. It does not pay your bills. Those savings come from displaced electricity and export income, whether or not your letter changes.

A sensible order of works

1. Check your current certificate on the EPC register. Note the score, not just the band, and read the recommendations page.
2. Do the cheap points first. Loft top-up, cavity walls where suitable, draught-proofing and heating controls. This is also the work the reformed fabric metric will reward.
3. Size solar to your electricity use and treat the EPC gain as a bonus. A 4kW system typically generates 3,400 to 4,200 kWh a year, against 3,000 to 4,000 kWh used by many households.
4. Re-assess after the works if you’re selling or letting, so the certificate reflects the improved home.
5. Keep the paperwork with your deeds. It helps the next assessor and the next buyer.

Getting solar onto your certificate

An EPC lasts ten years and shows the home as assessed on the day. Panels fitted the month after it was lodged add nothing until a new assessment is done. RdSAP 10 asks the assessor for the array’s peak power in kWp. The usual sources are the system specification or the wiring schematic near the meter, and the MCS certificate’s declared net capacity is the fallback. Batteries need photo or written evidence of make, model and usable capacity. If you bought a home with undocumented panels, ask your assessor early what they can record. Without paperwork the panels may be under-counted or left out.

FAQs