Are Batteries Worth It? Honest Maths

Are solar batteries financially worth it?

We modelled battery financial returns for 6 UK household types. A 10kWh battery (£5,000) added to a 4kW solar system: HOUSEHOLD 1 — Retired couple (home all day, 2,500 kWh/yr): Without battery self-consumption: 60%. With battery: 85%. Extra savings: £150/yr. Battery payback: 33 YEARS. VERDICT: NOT WORTH IT — high daytime use already captures most value. HOUSEHOLD 2 — Working couple (out 9-5, 3,000 kWh/yr): Without: 30%. With: 75%. Extra savings: £280/yr. Battery payback: 18 years. VERDICT: MARGINAL. HOUSEHOLD 3 — Family with EV (5,500 kWh/yr, Octopus Flux): Without: 35%. With: 80% + tariff arbitrage £200/yr. Extra savings: £480/yr. Battery payback: 10 years. VERDICT: WORTH IT. HOUSEHOLD 4 — WFH single (3,500 kWh/yr, Octopus Go): Without: 50%. With: 80% + overnight charging arbitrage. Extra savings: £350/yr. Battery payback: 14 years. VERDICT: BORDERLINE. HOUSEHOLD 5 — Large family (6,000+ kWh/yr, Flux): Extra savings: £520/yr. Payback: 10 years. VERDICT: WORTH IT. HOUSEHOLD 6 — Low-use flat (1,800 kWh/yr, flat tariff): Extra savings: £90/yr. Payback: 55+ years. VERDICT: NOT WORTH IT. KEY FINDING: Batteries are worth it for HIGH-consumption households on SMART TARIFFS. For low-consumption or flat-tariff households, the payback exceeds the warranty period. Sources: Ofgem price cap (ofgem.gov.uk), Octopus Energy tariff rates, battery manufacturer specifications.