Yield, savings and payback time of a plug-in solar system. Change modules, price and self-use share. Deutsch: Rechne mit eigenen Werten, wie sich ein…
# Balcony Solar: does it pay off?
# A plug-in solar system with a 800 W inverter. Change the inputs to match your place.
# Example values, check them for your case. Sources are named next to the inputs.
# Inputs
moduleCount = 2
modulePower = 430 W
# Full-load hours per year = yearly yield per installed kW.
# Fraunhofer ISE (as summarized by reduco.ai / logicenergy.de): rooftop fleet average about 922 h, new systems
# about 980 h. A balcony is often shaded or not ideally tilted, so this uses less.
fullLoadHours = 850 h
# Complete set with 2 modules and a 800 W inverter, offers range from about 300 to 600 € (selbst.de, homeandsmart.de)
systemCost = 450 €
# BDEW Strompreisanalyse 08/2026: household average 37.0 ct/kWh
# https://www.bdew.de/media/documents/BDEW_Strompreisanalyse_082026.pdf
electricityPrice = 0.37 € / kWh
# Share of the solar power you use yourself. Without a battery usually 30 to 50 % (selbst.de).
# Power you do not use is normally not paid for.
selfUse = 50 %
# Size and yield
installedPower = moduleCount * modulePower
yearlyYield = installedPower * fullLoadHours to kWh
# Savings
usedYourself = yearlyYield * selfUse
yearlySavings = usedYourself * electricityPrice / (1 year)
paybackTime = systemCost / yearlySavings to years
# After 20 years (modules lose about 0.5 % per year, ignored here)
savings20 = yearlySavings * 20 years
profit20 = savings20 - systemCost