Generator Backup Calculator

Calculate backup generator size and fuel cost for off-grid solar systems during low-sun periods.

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A backup generator supplements solar during extended cloudy periods, especially in winter. Size it to cover your daily shortfall in a 6-hour run window. A portable generator uses about 0.1 gallons per kWh. For off-grid systems, a propane or dual-fuel generator offers cleaner burning and longer shelf life than gasoline.