How much electricity does a rooftop solar system really produce?
Kilowatt peak is what you buy. Kilowatt hours are what you get. The gap between the two is decided by location, orientation, shade and heat.
Calculator · runs in your browser
Solar yield and payback calculator
Estimate the annual yield of a rooftop solar system, how much of it you use yourself, what it saves and when it pays back. Runs in your browser.
How the calculation works
The annual yield is system size times specific yield, adjusted for orientation and shade. The calculator spreads it over the twelve months with a typical monthly profile for the chosen climate zone, and simulates one representative day per month in quarter-hour steps: the sun's daily curve from sunrise to sunset, a household load profile with morning and evening peaks (and more demand in winter if a heat pump is included), and the battery charging from surplus and discharging in the evening.
- Savings combine the solar power you use yourself, valued at your electricity price, with the feed-in tariff for the rest.
- Payback is the investment divided by annual savings, without financing, price changes, subsidies or module ageing.
- CO₂ assumes each solar kilowatt hour displaces one kilowatt hour at the grid average you enter; 0.38 kg is roughly the German average of recent years.
- Real days are not all clear or all cloudy. A typical day per month smooths this out, so self-consumption is an estimate within a few percentage points, not a promise.
Background
All calculatorsGuides to go with it
Solar panels compared: TOPCon, heterojunction, back-contact and glass-glass
Module efficiency has crept above 22 percent, and the differences between technologies now show up more in heat, shade and looks than in the datasheet headline.
Home battery sizing: how many kilowatt hours do you actually need?
Bigger is not better. The right battery is the one that fills on most days and empties on most nights.