Solar BalanceUse a location-based production model as your starting point, then check whether it reflects the position and shading of your actual panels. A generic yield for an entire country can hide large differences between installations.
Model the panels you will install
In PVGIS, enter the location, total panel capacity, mounting arrangement, tilt and orientation. Use the intended balcony angle rather than an optimized roof angle. Record the annual kWh result and check the monthly pattern. PVGIS uses historical solar-resource information; it is not a forecast for a specific future year. PVGIS user manual
If you have an appropriate net specific yield instead, a rough calculation is:
Annual generation (kWh) = panel capacity (kWp) × net yield (kWh/kWp/year)
The yield must represent your location and panel arrangement, including the losses it claims to cover.
Check nearby shade separately
An upper balcony, railing, tree or neighboring building can block sunlight during important hours. PVGIS’s built-in terrain horizon represents hills and mountains; it does not automatically capture nearby houses and trees. Review shade across the day and through different seasons. A detailed site survey may be needed for a heavily obstructed balcony. JRC horizon documentation
Count each loss once
Temperature, wiring, conversion and other losses may already be included in your model result. When entering net AC generation in our payback calculator, do not subtract a blanket loss percentage again. Separate loss factors also multiply rather than simply add. JRC loss explanation
Use lower, central and higher generation inputs to see how the decision changes. These are illustrative scenarios, not probability ranges. Once the system operates, compare actual readings with the original assumptions and update your estimate.