How Many Solar Panels Do I Need?
Enter your power station's capacity and how fast you want it to recharge to find the total solar panel wattage you need.
“Peak sun hours” is the number of hours per day of sunlight strong enough to count as full-strength — most of the continental US averages roughly 3-4 hours in winter to 6-7 in summer, with 4-5 a common year-round planning average. Check a solar insolation map for your specific area for a precise figure.
Solar wattage needed for a full daily recharge
267W
3
100W panels
2
200W panels
1
400W panels
This sizes panels for a full recharge within one day's worth of peak sun hours — if you're fine recharging over two or three days instead, you can divide the required wattage accordingly and use a smaller, lighter panel setup.
How the How Many Solar Panels Do I Need? works
Enter your power station's capacity and your location's typical peak sun hours per day, and the calculator finds the total solar panel wattage needed for a full recharge within one day — then breaks that down into how many common panel sizes (100W, 200W, or 400W) that would take.
If a full one-day recharge isn't necessary for your situation, you can size for a slower multi-day recharge instead by dividing the recommended wattage by the number of days you're comfortable with.
Frequently asked questions
What are "peak sun hours" and why not just use total daylight hours?
Peak sun hours measure the equivalent number of hours per day at full-strength (1,000 W/m²) sunlight, which is a more useful planning figure than total daylight hours, since actual sunlight intensity varies throughout the day and with the seasons — a location can have 12 hours of daylight but only 4-5 peak sun hours.
Where can I find the actual peak sun hours for my location?
Solar insolation maps, published by sources like NREL (the U.S. National Renewable Energy Laboratory) and many solar equipment sites, show average peak sun hours by region and season — searching your city or region plus "peak sun hours" or "solar insolation map" turns up a specific figure more precise than a general average.
Should I size for winter or summer peak sun hours?
It depends on when you most need the backup power — sizing for winter's lower peak sun hours means your setup also comfortably covers summer, while sizing only for summer may leave you short during winter's shorter, weaker daylight.