How much solar to run a 12 V RV fridge

A small 12 V compressor fridge is often the biggest daily load in a van or trailer. In the RVWatt library a 50–65 L fridge uses 432 Wh a day. How much solar that takes depends on where you go and which month is weakest.

The formula the calculator uses is: solar watts = daily watt-hours ÷ (peak sun hours in your worst travel month × the system factor). With the default losses for an MPPT controller and LiFePO4 batteries, the system factor is 0.757. Battery size is a separate question: daily watt-hours × days without charging ÷ usable depth of discharge (0.8 for LiFePO4).

A 50–65 L 12 V fridge (432 Wh/day)

This is the fridge on the weekender and full-time van presets: 45 W × 24 hours × 40% duty. It is a conservative planning figure. Dometic’s official CFX3 45 and 55 numbers are about 297 and 317 Wh/day at 32 °C ambient, so many portable fridges will come in lower in mild weather and higher in the heat. Always check your own rating if you have it.

Place and season	Design month (flat roof)	Solar needed	Typical array	Battery, 2 days LiFePO4 at 12 V
Phoenix, AZ, May–October	October, 5.01 sun hours	114 W	1 × 200 W	90 Ah
Moab, UT, May–October	October, 4.34 sun hours	132 W	1 × 200 W	90 Ah
Denver, CO, May–October	October, 3.98 sun hours	143 W	1 × 200 W	90 Ah
Seattle, WA, May–October	October, 2.28 sun hours	250 W	2 × 200 W	90 Ah
Phoenix, AZ, December only	December, 3.08 sun hours	185 W	1 × 200 W	90 Ah
Hailey, ID, December only	December, 1.54 sun hours	371 W	2 × 200 W	90 Ah
Seattle, WA, December only	December, 0.85 sun hours	671 W	4 × 200 W	90 Ah

The battery stays at 90 Ah because two days of 432 Wh at 80% usable capacity is 432 × 2 ÷ 0.8 ÷ 12 V = 90 Ah, regardless of sun. In practice a 100 Ah LiFePO4 battery is the usual next size up. Solar is what changes with the map.

Seattle in December is the honest warning: 671 W of panels just to run the fridge, and the calculator flags sun under 1.5 peak hours. Solar alone is a poor plan there. Use shore power, a generator, or alternator charging, or travel somewhere sunnier that month. See peak sun hours by place.

Open the 50–65 L fridge in the calculator (Denver, May–October)

An 8–10 cu ft 12 V RV fridge (660 Wh/day)

Many modern travel trailers and Class C motorhomes now ship a large 12 V compressor fridge, not a propane absorption fridge. The Class C preset uses this load: 55 W × 24 hours × 50% duty = 660 Wh a day. That sits in the middle of measured figures — about 670 Wh/day in a Winnebago View Norcold 10 cu ft test, 524 Wh/day official for a Unique 10.3 cu ft at 25 °C, and owner reports of 600–750 Wh in mild weather.

Place and season	Design month	Solar needed	Typical array	Battery, 2 days LiFePO4 at 12 V
Phoenix, AZ, May–October	October, 5.01 sun hours	174 W	1 × 200 W	138 Ah
Moab, UT, May–October	October, 4.34 sun hours	201 W	2 × 200 W	138 Ah
Denver, CO, May–October	October, 3.98 sun hours	219 W	2 × 200 W	138 Ah
Seattle, WA, May–October	October, 2.28 sun hours	382 W	2 × 200 W	138 Ah
Denver, CO, year-round (December)	December, 2.29 sun hours	381 W	2 × 200 W	138 Ah
Seattle, WA, year-round (December)	December, 0.85 sun hours	1,026 W	6 × 200 W	138 Ah

Battery math: 660 × 2 ÷ 0.8 ÷ 12 V = 137.5 Ah, which the calculator reports as 138 Ah. A 150 Ah or 200 Ah LiFePO4 battery is the practical size. This is fridge only — lights, a CPAP or a furnace will add more. For a full trailer example see solar for a travel trailer.

Open the 8–10 cu ft fridge in the calculator (Denver, May–October)

Heat, duty cycle and charging below freezing

Compressor fridges work harder when the box, the vent or the day is hot, so the 40% and 50% duty cycles here can be low in midsummer. If you boondock in 100 °F weather, raise the duty cycle or the hours in the calculator rather than trusting a mild-weather number.

The battery figure does not change with the sun, but charging a LiFePO4 bank below 0 °C (32 °F) usually is not allowed. NASA’s monthly record minimums are below freezing in May, September and October in places like Denver and Moab — those are the coldest readings in each month over 2001–2025, not a typical night. If you may camp through a cold snap, use a self-heating battery or keep the bank inside the heated space.

Frequently asked questions

How many watts of solar do I need to run a 12 V RV fridge?

Divide the fridge’s daily watt-hours by peak sun hours in your worst travel month, then divide by about 0.757 for real-world losses with MPPT and lithium. A 432 Wh fridge in Denver from May to October (3.98 sun hours in October) needs 432 ÷ (3.98 × 0.757) ≈ 143 W, so one 200 W panel. The same fridge in Seattle that season needs about 250 W.

What size battery do I need just for the fridge?

For two days on LiFePO4 at 12 V: a 50–65 L fridge at 432 Wh/day needs 90 Ah, and an 8–10 cu ft fridge at 660 Wh/day needs about 138 Ah. In practice that is usually a 100 Ah or a 150–200 Ah battery. The battery size does not depend on how sunny it is.

Can I run a fridge on solar in winter?

Sometimes, but only where there is still useful sun. A 432 Wh fridge in Phoenix in December needs about 185 W. In Hailey, Idaho it needs about 371 W, and in Seattle about 671 W — enough that solar alone is usually the wrong plan. Add shore, generator or alternator charging, or travel farther south.

Does a bigger RV fridge need more solar?

Yes. The 8–10 cu ft 12 V fridge in the library uses 660 Wh a day, about 50% more than the 50–65 L van fridge at 432 Wh, so the array and the battery both scale up. A 120 V residential fridge is larger still, about 1,400 Wh from the battery plus inverter idle.

Related guides

Safety: high-current DC is dangerous. A 12 V battery bank can deliver thousands of amps into a short circuit, enough to melt tools, weld rings and watches to terminals, ignite insulation and start a vehicle fire in seconds. Lithium and lead-acid batteries can also vent, burn or explode if overcharged, damaged or charged outside their temperature limits. Remove jewelry, use insulated tools, disconnect the battery before working, fuse every positive conductor as close to the battery as practical with a fuse rated for the battery's short-circuit current (often a Class T for lithium banks), use properly crimped lugs and pure copper cable, and secure batteries against movement. If you are not confident, hire a qualified RV or marine electrician. RVWatt provides estimates only; see our Terms of Use.

These figures are planning estimates from typical appliance ratings and NASA monthly sun averages for a flat, horizontal panel. Your real use will differ with heat, shade, dirty panels and how you actually live in the rig. Follow your equipment manuals and have a qualified installer check high-current wiring.