Solar Panel Output Calculator
Estimate daily and annual energy output of a solar panel system from wattage and sun hours.
e.g. 5000 for a 5 kW system
Accounts for inverter, wiring, temperature, and soiling losses
Daily Output
Monthly Output
Annual Output
Calculation Steps
Understanding Solar Panel Output
The energy a solar array produces depends on three main factors: the rated size of the system in watts, how many peak sun hours your location receives, and a system efficiency factor that captures the unavoidable losses between the panels and your meter. A "peak sun hour" represents one hour of sunlight at 1,000 watts per square meter, the standard test condition for rating panels.
The Formula
- Daily kWh = (System watts ÷ 1000) × Peak sun hours × (Efficiency ÷ 100)
- Monthly kWh = Daily kWh × 30
- Annual kWh = Daily kWh × 365
What Reduces System Efficiency?
Typical Losses
- • Inverter conversion: ~4%
- • Wiring and connections: ~2%
- • Temperature (heat): ~5-10%
- • Soiling (dust, dirt): ~2%
Typical Efficiency Factors
- • New, well-sited system: ~80-85%
- • Average residential system: ~75-80%
- • Older or shaded system: ~65-75%
- • Default used here: 80%
References
The methodology and assumptions used in this calculator are based on established solar energy resources:
Note: This calculator provides estimates based on average conditions. Actual output varies with seasonal sun hours, panel orientation and tilt, shading, local weather, and panel degradation over time. For a site-specific estimate, consult a solar installer or use NREL's PVWatts tool with your exact location.