What Size Solar Panel Runs a 12V Fridge? 100W vs 200W vs 300W
Solar guide · 6 minute read · Written for car camping, van life and RV owners in the US
A solar panel's rating is a peak number, and you almost never see peak conditions. That is the whole problem with sizing a panel for a fridge: the arithmetic is simple, but the middle step — how much sun you actually get — is where people go wrong.
Get that step honest and the rest follows. Here is a three-step method, a comparison of three common panel sizes, and the reason a panel on its own will not do the job.
Why a panel's rating is not what you get
A panel rated at 100 W is rated at 100 W in full, direct sun, at a good angle, at a standard test temperature. In the real world you can expect less — sometimes a lot less. Four things pull the number down:
- Sun hours. A panel only produces near its rating for a few hours around the middle of the day. Call it half a day at best, and less in winter.
- Angle. A flat-mounted panel rarely faces the sun straight on, and off-angle means less output.
- Shade. Even a thin band of shadow across part of a panel can cut its output sharply.
- Heat. Panels lose a little output as they get hot, which is exactly when the sun is strongest.
The type of charge controller matters too. A simple PWM controller throws away some of what the panel collects, while an MPPT controller can harvest noticeably more. If you want to get closer to the panel's rating, MPPT is usually the better choice — but it costs more.
Put together, the rating is the ceiling, not the average. Plan below it.
The three-step method
- Work out the fridge's daily energy use in watt-hours (Wh). Running watts × the hours the compressor runs per day.
- Divide by realistic sun hours. Daily Wh ÷ good sun hours = watts of panel needed.
- Add a margin. Because real harvest is lower than the rating, round up.
Daily watt-hours ÷ realistic sun hours = panel watts, then add a margin
Example: a fridge that needs 450 Wh per day, in a spot with about 4 good sun hours, needs roughly 113 W of panel before any margin. Round up from there and you land nearer 150 W. The only firm numbers here are the arithmetic — the 450 Wh and the 4 hours are labelled assumptions you should replace with your own.
What 100W, 200W and 300W actually cover
The table below uses round example sun hours to show the method. Treat every figure as a best-case ceiling, because real harvest is usually lower.
| Example panel | Energy in good sun (assume 5 h) | Energy in poor sun (assume 2 h) | Roughly covers |
|---|---|---|---|
| 100 W | ~500 Wh | ~200 Wh | About one fridge-day in good sun; not enough in poor sun |
| 200 W | ~1,000 Wh | ~400 Wh | One fridge-day even in poor sun, with a little to spare |
| 300 W | ~1,500 Wh | ~600 Wh | One fridge-day with margin; around two in good sun |
These figures assume a fridge needing about 450 Wh per day (a round example) and a panel performing near its rating during the sun hours shown. Real harvest is lower, so treat them as the top of the range.
A panel does nothing without a battery in between
A solar panel does not power the fridge directly. It charges a battery or a power station, and the fridge draws from that. The battery is the buffer that lets a panel which only works in daylight run a fridge that works all night.
So the question is never just "what panel" — it is "what panel, charging what storage, for what fridge". A big panel feeding a tiny battery still runs out overnight. Size the pair together.
When 100W is enough, and when it is not
100W can work when
- You move most days and the vehicle's charging adds to what the sun gives you.
- Your fridge is small and its daily use is modest.
- You camp in summer, in open sun, at a decent angle.
Go bigger when
- You stay parked for several days with the fridge running the whole time.
- You camp in heat, in winter, or anywhere the sun is weak or the days are short.
- Your fridge is larger, or you want a real margin instead of a tight fit.
Want the numbers done for you?
The free 3-page Portable Fridge & Power Buying Checklist walks through this same formula, then the 7 fridge checks, the 8 station checks and the 24-hour test — in order.
Shade and winter change the answer more than most people expect
A panel in partial shade does not lose a little output — it can lose most of it. A single branch or a roof rack casting a shadow across part of a panel can pull the whole array down, well below its rating. If you camp under trees, do not size as if you were in the open.
Winter adds two problems at once: fewer daylight hours and a lower sun angle, so each of those hours delivers less. Both cut the daily harvest at the same time. If you camp off-season, size the panel up, or plan to top up from the vehicle as well. It is better to have sun you do not need than to need sun you do not have.
Quick answers
What size solar panel do I need for a 12V fridge?
Start from your fridge's daily watt-hours, divide by your realistic sun hours, then add a margin. There is no single correct number, because it depends on your fridge and your conditions — but as a rough starting point, a small setup in good summer sun often lands in the 100–200 W range, and you need more if you stay parked or camp in winter.
Can a 100W panel run a 12V fridge?
A 100 W panel can cover a small fridge's daily use in good sun, but it is tight and it will not keep up in poor sun, heavy shade or winter. Treat it as a maintainer rather than a guarantee, and check it against your own daily watt-hours before you rely on it.
Do I need a battery with solar?
Yes. A panel alone cannot run a fridge overnight or through a cloudy spell. The panel charges storage — a battery or a power station — and the fridge runs from that. Solar and storage are a pair, not alternatives.
Keep reading
- How much power does a 12V fridge use?
- What size battery for a 12V fridge?
- What size power station runs a 12V fridge?
- How long will a 12V fridge run on a 100Ah battery?
This guide may contain affiliate links. If you buy through them, we may earn a commission at no extra cost to you. We only link to products that fit the numbers above. Frostamp is not an electrician or an electrical engineer — this is general information, not professional advice. Always follow the manufacturer's instructions for your exact model.