Month-by-Month Bill Reduction

How much does solar reduce my electricity bill each month?

Month-by-month electricity bill reduction with a 4kW solar system (typical 3-bed semi, 2,900 kWh/yr consumption, 40% self-consumption, Ofgem cap 24.5p/kWh): WITHOUT SOLAR (monthly bill): Jan £85, Feb £75, Mar £70, Apr £62, May £55, Jun £50, Jul £48, Aug £50, Sep £58, Oct £68, Nov £78, Dec £88. TOTAL: £787/yr. WITH SOLAR (monthly bill): Jan £70 (save £15), Feb £55 (save £20), Mar £40 (save £30), Apr £20 (save £42), May £5 (save £50), Jun -£5 (save £55 — NET CREDIT), Jul -£10 (save £58 — NET CREDIT), Aug £0 (save £50), Sep £18 (save £40), Oct £40 (save £28), Nov £62 (save £16), Dec £75 (save £13). TOTAL WITH SOLAR: £370/yr. ANNUAL SAVING: £417/yr without battery. WITH BATTERY (65% self-consumption): Annual bill drops to £220/yr. Saving: £567/yr. KEY INSIGHT: June and July bills can go NEGATIVE (you earn more from SEG export than you spend on grid electricity). Summer essentially gives you free electricity plus a small income. Sources: PVGIS monthly generation data (re.jrc.ec.europa.eu), Ofgem cap Q1 2026 (ofgem.gov.uk), BEIS seasonal consumption profiles.