Off-Grid Solar Calculator
Estimate the solar array and battery storage needed to support a daily off-grid electricity load.
Off-grid system example
Example: 12 kWh/day load, 4 peak sun hours, 20% solar losses, 400 W panels, 2 days of autonomy, 90% usable battery depth of discharge and 90% battery/inverter efficiency.
Battery: 12 × 2 ÷ (0.90 × 0.90) = 29.63 kWh
At 400 W per panel, the array rounds up to 10 panels or 4.0 kW.
Why winter conditions matter
Off-grid systems must produce enough energy during periods when solar conditions are poor. A system sized from annual-average sun hours may be too small in winter or during extended cloudy weather. Generator backup, load shedding or a larger array and battery bank may be needed.
Off-grid solar FAQ
What does autonomy mean?
Battery autonomy is the number of days the battery is intended to support the entered daily load without new solar energy.
Does this size the inverter?
No. Inverter sizing depends on simultaneous load, surge demand, motor starting current, voltage and system architecture. This calculator estimates energy capacity, not equipment power ratings.
Should I use average or winter peak sun hours?
For critical off-grid systems, use a conservative value that represents the difficult season for your location and design objectives.
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