Camper Van Solar Calculator
Enter your van appliances and roof space — get a complete solar system spec for your build.
How to Use This Calculator
Choose your camper type and roof space
Start by selecting your camper type — this determines the panel format the calculator recommends. Cargo vans and Sprinters typically use flexible or slim rigid panels (100W each) that mount flush to the roof. Skoolies and buses have flat roofs that fit standard rigid 200W panels. Enter your actual available roof space in square feet — measure the flat, unobstructed area excluding roof vents, skylights, and AC units.
Enter each appliance
Go through the appliance list and enter the watts each device draws and the hours per day you use it. The 12V compressor fridge (like a BougeRV or Iceco) should be set to 24 hours because it cycles continuously — 40-60W at average is typical. The roof fan (Maxxair or Fan-Tastic) runs most of the night in summer. The diesel heater only draws 10-30W for its fan; the fuel doesn't count toward electrical load.
Set boondocking days and sun hours
Boondocking days drives battery bank size — it's how many nights you need to run on battery alone without solar charging. Van lifers in mixed climates typically plan for 2-3 days. Peak sun hours determines how much your panels actually produce each day. Southwest desert: 5.5-6.5. California coast: 5.0. Pacific Northwest: 3.5-4.5.
Read the output
The results show total solar watts, panel count, battery Ah (separately for AGM and lithium because they have very different usable capacity), charge controller amps, and inverter size. If your roof can't fit enough panels, a warning tells you — the fix is usually higher-wattage flexible panels or supplemental charging from shore power or a DC-DC charger from the alternator.
The Formula
The 80% system efficiency accounts for MPPT conversion losses, wiring resistance, and temperature derating on hot metal roofs (vans get hot). The depth of discharge (DoD) difference between AGM (50%) and lithium (80%) is why lithium batteries can be nearly half the Ah for the same usable capacity — the Ah rating is the same, but you can actually use more of it.
Example
Alex — Full-time Sprinter conversion, Pacific Coast
Alex works remotely from a high-roof Sprinter with 80 sq ft of roof. They run a laptop 6 hours, a compressor fridge 24/7, a roof fan all night, and charge phones and lights. They travel the Pacific Coast (4.5 peak sun hours) and want 3 days of battery backup.
Result
Five 100W flexible panels fit the Sprinter roof easily. For batteries, 560 Ah of lithium (e.g., two 280Ah cells) is far more practical than 895 Ah of AGM — lighter, smaller, and faster to charge. Alex can run three fully cloudy days before the battery hits 20% reserve. The 52A MPPT controller (e.g., Victron SmartSolar 75/50) is ideal for this 500W array.