What Size Solar Panel Do You Need for a 12V Fridge?

Solar is what turns a fridge setup from “two or three days” into “as long as the food lasts.” The sizing question has a straightforward answer once you know how much energy your fridge uses in a day and how much sun you’ll actually get. This guide gives the formula we use in our battery runtime calculator, worked examples for different fridges, and the mistakes that leave people with a flat battery under a sunny sky. We haven’t tested panels ourselves. The inputs come from maker specs and our own published estimates.

What’s the formula?

solar watts needed = daily Wh ÷ peak sun hours ÷ 0.75

• Daily Wh is what your fridge uses in 24 hours, at your temperatures.
• Peak sun hours is the equivalent number of hours of full, bright sun your panel gets in a day. Five hours of “peak sun” usually means a whole day of real sunshine, not five hours of daylight.
• 0.75 covers the losses between the panel’s label and your battery: charge controller, wiring, heat, dust and a panel that isn’t aimed perfectly. Portable panels rarely make their nameplate watts.

The result is the panel size that breaks even, replacing what the fridge used that day. You’ll want some margin above it.

Step 1: How much energy does your fridge use per day?

Only one fridge we track publishes a fridge-mode daily figure. EcoFlow rates the GLACIER Classic 35L at 165 Wh per 24 hours at 77°F outside and 39°F inside, in Eco mode. Dometic publishes an hourly figure for the CFX3 45 (1.03 Ah/h at 90°F), which works out to about 300 Wh a day. For every other model we estimate from capacity. Our chart shows those estimates at 90°F outside and 37°F inside:

The bars are estimates for steady running with the lid mostly closed. Freezer settings, hot sun on the fridge and warm food going in all push the real number up. In real camping, Gnomad Home measured an ICECO VL35 ProS averaging about 508 Wh a day. If you can measure your own fridge with a battery monitor, use that number instead.

Step 2: How many peak sun hours will you get?

This varies more than people expect. The US Department of Energy points out that solar radiation depends on location, season, time of day, landscape and weather. Its example: Denver gets nearly three times more solar energy in June than in December. Thick clouds can block direct sunlight entirely.

Rules of thumb we use:

• Summer, open sky, panel aimed at the sun: 5–6 hours. Dometic tells CFX owners to plan on roughly 6.
• Spring or fall, or a panel lying flat: about 4.
• Winter, cloudy forecasts, or a campsite under trees: 3 or less.

Shade is the big one. A panel in partial shade can lose much of its output, so a portable panel you can move into the sun often beats a bigger panel fixed to a roof in a shaded campsite.

Worked examples

All examples use the formula above. Daily figures are our estimates unless noted.

How to read it: for a typical 45-quart fridge in summer, a 100 W panel breaks even in good sun with a little margin. It falls behind on a cloudy day, so your battery covers the gap. For a dual zone running a freezer, plan on 200 W or more. The Renogy 200W solar suitcase and the EcoFlow 220W bifacial panel are on our list.

Step 3: Size the battery to cover the gaps

Solar only works in daylight. Your battery has to carry the fridge through the night and through any day when the panel falls short. Dometic’s own recommendation is a 100 W or larger panel with at least a 40 Ah battery. For multi-day trips, we’d size the battery to cover at least a night plus one poor solar day. For a 45-quart fridge that’s roughly 300–600 Wh of usable capacity, which a 100 Ah LiFePO4 covers comfortably. Our battery runtime guide has the math.

How do you connect the panel?

There are three common ways:

1. A fridge with a built-in battery and solar input. Per the makers, the Anker EverFrost 2 40L takes up to 100 W at 12–30 V, the GLACIER Classic up to 110 W at 11–30 V, and the BougeRV CRD2 V2.0 + 240Wh up to 150 W at 12–32 V. Anker notes that solar charging only works with a battery inside the cooler. A 100 W folding panel matches these inputs. Check that the connector fits first.
2. A power station. Plug the panel into the power station’s solar input and the fridge into its 12 V outlet. Gear Diary topped up a power station running an ICECO VL60 by setting up a 350 W panel array for about six hours.
3. A 12 V house battery. You need a solar charge controller between the panel and the battery. A suitcase panel with a built-in controller is the simplest way.

Whichever you use, don’t exceed the input’s voltage or wattage limit. Too high a voltage can damage the electronics. Too much wattage is usually just wasted.

Mistakes that leave you with a flat battery

• Sizing from the panel’s label, not real output. That’s why the formula divides by 0.75.
• Planning around summer sun on a fall trip. Shorter days and a lower sun cut output a lot.
• Parking in shade to keep the fridge cool, then putting the panel in the same shade. Run a longer cable and put the panel in the sun.
• Forgetting the freezer. EcoFlow’s own figures for the GLACIER Classic show freezer mode using about three times the energy of fridge mode (520 vs 165 Wh a day at 77°F). Size for the setting you’ll actually use.
• No battery buffer. One cloudy day shouldn’t end your trip.

Bottom line

For a single-zone fridge of 45 quarts or less, 100 W of solar plus a decent battery keeps up in summer. Smaller and more efficient fridges can get by with less. For a dual zone with a freezer, or for winter and shady sites, plan on 200 W or more. Start from your fridge’s real daily energy, divide by honest sun hours and 0.75, then round up. The battery runtime calculator shows the solar break-even for your fridge and temperatures.