Solar Panels for Refrigerator

BACKUP POWER EXPLAINED · SOLAR & BATTERIES

Two 200-watt solar panels can cover the daily energy use of a refrigerator that uses 1 kWh per day if you get four peak sun hours. With only two peak sun hours, the same fridge would need four 200-watt panels under the assumptions below. A battery keeps the fridge running overnight, and the inverter must handle the compressor’s startup demand.

1. Find out how much energy your refrigerator uses

Start with the kWh per year number on the yellow EnergyGuide label. Divide it by 365 to estimate daily energy use. A fridge rated at 365 kWh per year averages 1 kWh per day, or 1,000 watt-hours (Wh). If you don’t have the label, try the Department of Energy’s refrigerator and freezer energy rating tool.

For an estimate based on your actual fridge, use a plug-in energy meter rated for the appliance and measure over several normal days. That captures compressor cycling and defrost cycles. If you’re backing up a garage fridge, try to measure it under conditions similar to those you expect during an outage.

2. Size the solar panels for the sunlight you expect

Panel watts needed = daily fridge use in Wh ÷ (peak sun hours × estimated system efficiency)

Peak sun hours describe how much solar energy you get in a day, expressed as equivalent hours at full sunlight. Use PVWatts to look up monthly solar resource for your location and panel orientation. Monthly averages are a starting point. Actual output on a cloudy outage day can be much lower.

Using 75% as a rough planning factor for real-world solar and conversion losses, a refrigerator using 1,000 Wh per day needs about 333 W of solar panels with four peak sun hours. If you’re buying 200 W panels, round up to two panels for 400 W total.

For a Wisconsin winter outage, check your winter solar estimates and run a low-sun scenario. Clouds, shade, and snow cover can all cut into production. Before buying panels, check the power station or charge controller manual for compatible panel configurations and solar input limits for voltage, current, and watts.

3. Size the battery for overnight and the inverter for startup

If a fridge uses 1,000 Wh per day and that use is spread evenly, it needs about 500 Wh at the outlet over 12 hours. At 85% inverter efficiency, that draws roughly 590 Wh from the battery. A full 24 hours without solar would draw about 1,180 Wh.

Allow extra capacity for inverter idle draw, other devices, and a reserve. Check the battery’s usable capacity, since the advertised capacity may be higher. A fully charged 1,000 Wh power station may cover the overnight example, but it falls short of the full-day example even before those extra allowances.

The fridge in this example averages about 42 W across the day. Its compressor can draw substantially more when it starts. Check the inverter’s continuous rating against the fridge’s running demand and its surge rating and duration against the compressor’s startup demand. Test your actual fridge and power station together before relying on them during an outage.

Can I use the solar panels already on my roof?

Standard grid-tied solar typically shuts down when utility power goes out. To use rooftop solar during an outage, your system must be designed to supply backup power while isolated from the grid. Check which outlets or circuits it backs up and whether the panels can recharge the battery during an outage. With a portable setup, plug the fridge into a compatible power station’s AC outlet as directed by the manual. See the Department of Energy’s guide to solar and resilience.

Start with your fridge’s daily energy use. Then size your panels for the low-sun conditions you want to plan for and your battery for the longest stretch you expect to go without charging.

Related guides

• How Long Will a 100Ah Battery Run a Refrigerator?
• How to Combine Solar Panels, Batteries, and a Backup Generator