Work out solar payback period instantly with clear inputs, formula shown and shareable results.
Payback is installed cost divided by annual saving, but the saving depends heavily on how much generation is self-consumed: exported units usually earn far less than the retail tariff avoided by self-use. Levelised cost of energy divides the capital cost by lifetime generation, allowing comparison with the grid tariff directly.
Solar payback
saving = self-used kWh x tariff + exported kWh x export rate; payback = cost / saving
Avoiding a 29 cent purchase is worth far more than earning a 5-15 cent export rate, so shifting loads into daylight hours shortens payback substantially.
Yes. Panels lose roughly 0.5% of output per year, so lifetime generation is about 94% of the naive 25-year figure.