enter your city、capacity and consumption/feed-in tariff，estimate annual generation of a home rooftop PV system、annual revenue and payback years。free、no registration required。
annual generation = installed capacity(kW) × city annual utilization hours（kWh/kWp·year，already includes system efficiency derate）。self-consumption revenue = generation × self-consumption ratio × self-use tariff；electricity sales revenue = generation × feed-in ratio × feed-in tariff。the sum of both plus subsidies is the annual revenue，divide total investment by annual revenue to get the payback period。
about the parameters：annual utilization hours already imply about 80% system efficiency and shading derate；the feed-in tariff references local coal benchmark prices/benchmark grid-parity price（about 0.35–0.45 yuan/kWh）；system unit price 2025–2026 home PV typically 3–4 yuan/W。this tool estimates by first-year generation，not including module degradation of about 0.5% degradation，long-term returns will be slightly lower。
when the payback falls within 6–8 year within、and plans self-consumption 10 for over N years，home PV usually has good economics；higher self-consumption ratio is more cost-effective（saved electricity cost exceeds sold electricity price）。grid-connection policy、roof ownership and local subsidies vary widely，results are for investment estimation reference only，please defer to local utility and installer quotes。