Use this for an initial planning range
The calculator converts daily energy use into a starting PV array using peak-sun hours and an allowance for system losses. The battery estimate uses backup hours and average backup load. The inverter estimate is intentionally conservative and should be replaced by an appliance-by-appliance peak and surge check before equipment is purchased.
Solar system size calculator
Planning estimate only. Final design must check load profiles, motor surge, roof layout, PV string limits, battery current, temperature, shading and local electrical rules.
How to choose the inputs
Daily electricity use
Use measured kWh from a bill, smart meter or energy monitor when possible. If you only have appliances, build an estimate with the appliance load calculator.
Peak sun hours
Peak-sun hours are not the same as daylight hours. They summarize solar resource as equivalent full-sun hours. For a serious production estimate, use a location-specific model such as NREL PVWatts or another bankable local resource dataset.
Backup hours and average backup load
Backup energy is driven by the loads that remain on during an outage. If you plan to shed air conditioning, water heating or other large loads, use the reduced average backup load rather than the whole-home average.
Why the result is not a final design
Final design must consider roof layout, shading, module/inverter string limits, temperature, battery current, motor surge, local electrical rules and the exact equipment selected.