How Many Watts of Solar Does a Shed Actually Need?
Summary
It depends on what runs inside, not on the shed's floor area. A 20 W LED light for 3 hours, a 5 W camera around the clock, and 60 Wh of tool-battery charging add up to 240 Wh a day. Averaged over a year, NLR's PVWatts puts a single 100 W panel at roughly 300 Wh a day in Seattle and 480 Wh in Phoenix, so 100 W covers that load on paper.
Count watt-hours, not square feet
Take a shed with a light, a camera, and a charger.
- LED light, 20 W for 3 hours: 60 Wh
- Security camera, 5 W for 24 hours: 120 Wh
- Tool-battery charging, once a day: 60 Wh
That is 240 Wh. The wattages here are examples; the real ones are on each device's label or in its manual. The 300 to 480 Wh range for 100 W is a yearly average for a fixed, south-facing panel tilted 20 degrees, so short winter days fall below it.
Night hours and empty weekdays
Solar only produces while the sun is up. The Department of Energy notes that batteries let solar power a home at night or when weather blocks the sun. With a camera running all night, the overnight share of its 120 Wh has to come out of storage.
A 2008 Sandia National Laboratories report for DOE describes off-grid PV as usually including storage to hold unused power for later low-light conditions, and says that when storage is full, PV output is throttled back and the available energy is discarded. A shed that sees people only on weekends fills its battery early in the week and wastes the rest. How much you can use across a Saturday and Sunday depends less on panel watts than on what the battery holds plus two days of production.
Tools draw watts, not just watt-hours
A watt-hour is an amount; a watt is a rate. Running a 1,000 W tool for 10 minutes uses about 167 Wh, less than the daily total above, but an inverter that cannot supply 1,000 W will not start it. The same Sandia report explains that a stand-alone inverter has to supply current as needed to hold its AC voltage, and that battery storage is what covers power demand surges.
Shopping for one? Browse RV and off-grid solar panels →
Sources
- National Laboratory of the Rockies — PVWatts API Version 8 (modeled by SolarPanelX on September 23, 2026: 1 kW system, south-facing, 20° tilt, fixed roof mount, standard module, 14% losses; scaled to 100 W)
- U.S. Department of Energy — Solar Photovoltaic System Design Basics
- Sandia National Laboratories (U.S. DOE) — Renewable Systems Interconnection Study: Distributed Photovoltaic Systems Design and Technology Requirements (SAND2008-0946 P, February 2008)
We have not tested these products. Specs, prices, stock and terms are as published on these pages on the date above and can change; check the manufacturer or retailer before you buy.