How long could your solar panels take to pay for themselves?

Reviewed 20 October 2026. Shared model FB-hourly-1.0.0; profiles FB-synthetic-2026-10-20. An 8,760-hour representative year serves household demand from solar first, stores surplus within capacity and power limits, then uses stored energy later. Round-trip losses are applied once at discharge; opening and closing storage balances converge. No grid charging, tariff arbitrage or export restriction is assumed.

Total annual benefit = avoided imports × import price + export income − annual operating costs. Simple cash payback = your installed cash price ÷ positive first-year benefit. Battery-inclusive savings already include solar savings; they are not added twice. Standing charges are not saved. Degradation, standby use, maintenance, replacements and finance are excluded.

Profiles are original Fairbeam synthetic assumptions (CC0-1.0), not PVGIS weather or measured households: a 365-day standard-time year without daylight-saving changes, summer-weighted generation and winter-weighted demand. Smooth hourly profiles can overstate storage benefit during cloudy spells and miss short peaks. Your selected habits adjust the same appliance-based household profile used by the battery tool.

Import reference: 26.32p/kWh, Ofgem GB average Direct Debit, October–December 2026. Estimates pause after this period. Export 0p/5p/15p cases are illustrations; eligibility and supplier terms vary. NI estimates are withheld. No forecast of future tariffs is made.

Read the shared equipment, household assumptions and source references. Panel count alone does not establish actual kWp. Counting panels and batteries does not establish their exact performance. For a tailored estimate, ask your installer to use your roof, equipment and actual household usage.