Total electricity used per year (check your utility bill).
Location
hr/day
Average daily hours of peak sunlight (1,000 W/m²) from NREL data.
System Preferences
Higher wattage = fewer panels. Most homes use 400W panels (2024 standard).
78%
60%95%
Accounts for inverter, wiring, temperature, and soiling losses. Default 78% is typical.
South-facing roofs produce the most energy. East/West ~85%. North is least efficient.
Recommended System Size
7.2
kW
Based on 11,250 kWh/yr in California
Number of Panels
18
400W panels
Annual Production
11,275
kWh/yr
Monthly Production
940
kWh/mo avg
Estimated Roof Area
315
sq ft (17.5 sq ft/panel)
Annual Savings
$1,804
at $0.16/kWh
25-Year Savings
$68,400
3% escalation, 0.5% degradation
CO₂ Offset
4.4
tons/yr
Trees Equivalent
200
trees/yr CO₂ absorption
Monthly Energy Production
Estimated kWh generation by month
This calculator provides estimates for educational purposes only. Actual solar system performance depends on local weather, shading, roof condition, installation quality, and other factors. Electricity rates and utility policies vary by provider. Consult a qualified solar installer for a site-specific assessment. Peak sun hours from NREL NSRDB.
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