Solar sizing
How Much Solar Do You Need?
Many people believe, “I have a 200W panel, so I make 200W.” That is almost never true. Real-world solar is about averages, losses, and how much energy you need to replace each day.
Solar replaces battery energy
Solar usually does not power your gear directly. It replaces watt-hours removed from the battery.
Solar watts x peak sun hours = daily energyPeak sun hours
Peak sun hours are the usable sunlight equivalent for solar production. They are not the same as daylight hours.
| Location / season | Example peak sun hours |
|---|---|
| Montana summer | About 5.5 hours |
| Arizona summer | 6+ hours |
| Washington winter | About 2 hours |
200W panel example
For a 200W panel in Montana summer:
200W x 5.5 hours = 1,100Wh/dayIt is not:
200W x 24 hoursSolar output depends on time of day, clouds, heat, dust, panel angle, and tree cover.
Fridge example
If your fridge consumes about 500Wh/day, your solar needs to replace about 500Wh/day to break even.
500Wh/day / 5 peak sun hours = 100W minimumA 100W panel might work in ideal conditions. A 200W panel is smarter because weather exists.
Why bigger solar wins
More solar means faster recovery, less battery cycling, and better cloudy-day resilience. Many experienced overlanders end up around 200-400W because it creates margin.
Roof panels vs portable panels
Roof panels charge whenever the rig is in the sun. Portable panels can be aimed and moved, but they require setup. A strong system can use both.