Energy efficiency
Solar panels and EPC ratings: do they actually make a difference?
6 min read · Updated May 2026
Solar panels appear on a lot of EPC improvement recommendations. But their impact on the EPC rating is often overstated — and the financial case depends heavily on your roof and how you use electricity. Here's an honest breakdown.
How solar panels affect EPC ratings
Solar panels improve EPC ratings by reducing the property's net energy consumption — the electricity generated on-site offsets what would otherwise be drawn from the grid. In the SAP methodology, this counts as a direct improvement to the property's energy performance.
Typical rating improvement from a 4kW solar panel system:
- On a D-rated property: typically 4–8 SAP points — may or may not be enough to move a band
- On a C-rated property: typically 3–6 SAP points — often pushes to B
- Combined with a heat pump: significantly higher — the combination is greater than the sum of its parts
The honest truth: solar panels alone are rarely enough to transform a low EPC rating. They're a meaningful improvement but not a silver bullet. Insulation and heating system changes move the needle more.
What solar panels cost in 2026
| System size | Typical cost | Annual output |
|---|---|---|
| 3kW (6 panels) | £4,000–£6,000 | ~2,700 kWh |
| 4kW (8 panels) — most common | £5,000–£8,000 | ~3,600 kWh |
| 6kW (12 panels) | £7,000–£11,000 | ~5,400 kWh |
| Battery storage add-on | £2,000–£4,000 | Stores excess generation |
Output estimates based on UK average irradiance, south-facing roof, no shading. North-facing can reduce output by 30–40%.
What they save annually
Savings come from two sources:
- Self-consumption — electricity you generate and use directly, avoiding grid purchase at ~25p/kWh. A 4kW system might save £300–£500/year this way.
- Export tariff (Smart Export Guarantee) — excess electricity sold back to the grid at 4–15p/kWh depending on your tariff. Adds £50–£150/year typically.
Total annual saving: typically £400–£650/year for a 4kW south-facing system. Payback period: 8–14 years without battery, potentially shorter with battery if you have a heat pump or EV charger.
Is your roof suitable?
The key factors:
- Orientation — south-facing is optimal (100% output). East or west-facing still works well (75–85%). North-facing is poor (50–60%) and rarely worth installing.
- Pitch — 30–40° angle is optimal. Flat roofs can work with angled mounts.
- Shading — trees, chimneys, or neighbouring buildings casting shadows significantly reduce output. Even partial shading on one panel can affect a whole string.
- Condition — panels last 25+ years. If the roof covering is 15+ years old, consider replacing it before installing panels to avoid removing them for roof repairs later.
- Listed buildings and conservation areas — may require planning permission. Standard properties don't need planning for solar on the main roof.
Solar panels + heat pump: the best combination
The combination of solar panels and a heat pump is the most powerful EPC improvement strategy available. The solar panels generate electricity during the day; the heat pump uses that electricity to heat the home. Together they can push a C-rated property to A in the right conditions.
This also addresses the heat pump's main financial weakness — high electricity costs. Running a heat pump on self-generated solar electricity dramatically reduces its running costs.
Buying a property that already has solar panels
If you're buying a property with solar panels already installed, check:
- Age and warranty — panels typically come with a 25-year performance warranty. Ask for documentation.
- Feed-in Tariff (FiT) — properties with panels installed before April 2019 may have a Feed-in Tariff contract, which pays a fixed rate for all generation (not just export) for 20 years. This is transferable to a new owner and is valuable — potentially £500–£1,000/year.
- Ownership — some older installations were done under “rent-a-roof” schemes where the solar company owns the panels and takes the FiT income. Check who owns them.
The short version
- Solar panels improve EPC ratings by 4–8 SAP points typically — meaningful but not transformative alone
- A 4kW system costs £5,000–£8,000 and saves £400–£650/year
- South-facing roofs with no shading are optimal — north-facing rarely makes sense
- Combined with a heat pump, the EPC and financial impact is significantly higher
- If buying a property with existing panels, check for a Feed-in Tariff contract — it could be worth £500–£1,000/year
Related guides