RV solar sizing is not "buy the biggest panel that fits." It is reconciling how many watt-hours you spend between sunrise and sunset with how many watt-hours your roof can harvest in real campground conditions—partial shade, tilt you did not bother setting, and a fridge that cycles all night on battery.
Build a load ledger first
List every device: compressor fridge, furnace fan, lights, water pump, inverter idle draw, and phantom loads from USB chargers. Note which run on 12 V DC natively vs. through an inverter—conversion tax belongs in the ledger.
Daily Wh budget vs. peak watts
Daily energy sets panel wattage targets. Peak watts set inverter and fuse sizing for microwave or coffee bursts. Undersizing daily Wh leaves you running the generator every evening; undersizing peak watts trips breakers even when the battery is full.
Roof real estate and mounting constraints
Measure unobstructed length × width per plane, subtract vents, AC shrouds, and walkway clearance. Curved motorhome roofs may favor flexible panels or tilt kits on brackets—flat arrays on curved surfaces gap and flutter. Factor wiring home runs: parallel strings need combiner fusing near the charge controller.
Yield is not nameplate STC
Campground partial shade can cut harvest fifty percent without obvious shadows on your panel face—trees line-of-sight at low sun angles matter. Use conservative peak sun hours for your travel regions, not desert brochure numbers, when sizing.
Portable power stations as a hybrid strategy
Many owners pair roof solar with a portable station for desk work or outdoor kitchens. Recharge time from solar depends on station input limits (often 100–400 W max DC input) independent of how large your roof array is—oversized roof watts cannot push faster than the station accepts.
Commissioning checklist
- Verify charge controller profile for lithium if applicable
- Torque mounts and seal penetrations
- Log one dry-camping night: morning SOC, evening SOC, loads used
- Adjust tilt seasonally if you use adjustable legs
Right-sized RV solar feels boring: fridge cold, lights on, generator quiet. Wrong-sized solar feels like a hobby that never ends—start with honest Wh math, then buy hardware.