Most RVs running a fridge, lights, and electronics need 200 to 400 watts of solar. That answer comes from arithmetic you can do yourself in five minutes, and doing it yourself beats any rule of thumb, so here is the whole method.
Step 1: add up your daily watt-hours
List what you actually run and estimate honestly. Some defensible working numbers:
- 12V compressor fridge: 300 to 600 Wh per day. It cycles on and off around the clock, and hot weather pushes it toward the high end. This is almost always your biggest load.
- LED lights: about 50 Wh for an evening. A handful of 5 to 10W fixtures for a few hours.
- Two phones: about 30 Wh.
- Laptop: 50 to 60 Wh per full charge.
- Vent fan, water pump, odds and ends: 50 to 100 Wh.
That totals roughly 500 to 900 Wh per day for a typical two-person setup. If you see a build video claiming a fridge, fans, lights, and a laptop on 200 Wh a day, someone is not counting the fridge.
Air conditioning, electric heat, and induction cooking are not on the list because rooftop solar on an RV does not run them. Those are generator or shore power loads.
Step 2: divide by real sun hours
A “peak sun hour” is an hour of full-strength sun. Even in good conditions, count on 4 to 5 usable hours a day, not daylight hours. Morning and evening sun is weak, and shade from one tree branch craters a panel’s output.
For a 700 Wh day: 700 divided by 4.5 hours is about 155W of harvest you need during those hours.
Step 3: derate, because nameplate watts are laboratory watts
A 200W panel delivers 200W in a lab. On your roof it will not, for reasons that stack:
- Flat mounting. Panels laid flat on a roof miss the ideal sun angle most of the day, and most RV panels are mounted flat.
- Heat. Panels lose output as they get hot, and a roof in summer is hot.
- PWM controllers. Cheap starter kits ship PWM charge controllers instead of MPPT. The Renogy 400W starter kit, for example, includes a PWM Wanderer; the MPPT version costs more. MPPT recovers power a PWM controller leaves on the table, especially in cold weather.
Stacked together, a realistic planning number is 60 to 70 percent of nameplate during your sun hours. So that 155W of needed harvest becomes 220 to 260W of nameplate panel. Then add margin for the overcast day, because there will be one: land at 300W, or 400W if your fridge runs big or you park in the trees. That is how 500 to 900 Wh a day becomes the standard 200 to 400W answer.
The worked example, all at once
700 Wh per day, divided by 4.5 sun hours, is 155W needed. Divided by a 0.65 derate, that is 240W of panel. Round up for weather margin: 300W. A 100Ah LiFePO4 battery (about 1,280 Wh) covers a full day with room to spare.
Your numbers will differ, which is the point. Run your own loads through our RV solar calculator and get an answer that is about your rig instead of a typical one. When you know your wattage, the kits worth the money (and the controller trade-offs in each) are compared in best solar kits.
Kit pricing and controller details verified on Renogy’s product page July 17, 2026.