Solar Panel & Battery Payback: Real Numbers for East Anglia Homes

2026 Starting Numbers for East Anglia

To calculate solar payback we need: electricity unit rate (currently 24.5p/kWh on standard tariff, averaging ~22p/kWh across the year), standing charge (£0.61/day), and local solar generation data. East Anglia receives 1,040–1,080 kWh/m²/year of solar irradiance — around 10–12% above the UK average — which improves both generation and payback versus national benchmarks.

4 kW System: The East Anglia Baseline

A 4 kW solar system in East Anglia generates approximately 3,600–3,800 kWh per year. A typical 3-bedroom household consumes 3,500–4,500 kWh annually. Without battery storage, you self-consume around 30–40% of generation (the portion used as it's being generated during the day). The remaining 60–70% is exported at SEG rates of 4–15p/kWh.

Annual savings breakdown for a 4 kW system without battery: self-consumption savings (1,200 kWh × 24.5p) = £294; SEG export earnings (2,400 kWh × 7p average) = £168. Total annual benefit: approximately £462. Installed cost: £6,500. Payback: 14 years. Returns are decent but storage dramatically improves them.

4 kW Solar + 9.5 kWh Battery: The Optimised System

Adding a 9.5 kWh battery increases self-consumption from 35% to 75–85%. Annual savings: self-consumption savings (2,800 kWh × 24.5p) = £686; SEG export earnings (800 kWh × 7p) = £56. Total annual benefit: approximately £742. Installed cost: solar £6,500 + battery £3,200 = £9,700. Payback: 13 years. The incremental cost of adding the battery (£3,200) produces additional annual savings of £280 — giving the battery alone a payback of just under 12 years.

On Octopus Flux or similar time-of-use tariffs, the combined system saves an additional £400–£600 per year through overnight charge-and-discharge arbitrage. This compresses system payback to 8–10 years and generates genuinely compelling whole-life returns.

25-Year Whole-Life Return

Solar panels carry 25-year performance warranties and routinely perform well beyond 30 years. Over 25 years, a 4 kW + battery system in East Anglia produces cumulative savings and SEG income of approximately £18,500 (at static electricity prices) to £26,000 (assuming 3% annual electricity price increases). Capital invested: £9,700. Net benefit over 25 years: £8,800–£16,300. IRR: 7–12% — comfortably outperforming most savings accounts or ISA returns over the same period.