Van Solar Components
Panels and a battery are only half a system. These pages size the charge controller, the inverter, and the cable and fuse that connect them. For a whole build in one pass, use the calculator.
Wire Size & Voltage Drop Calculator
Interactive tool: enter watts, voltage and cable length for the AWG, the fuse, and the voltage drop, using ABYC figures.
MPPT Charge Controller Calculator
Interactive tool: array watts and battery voltage in, controller amperage out, with the cold-weather margin applied.
Inverter Size Calculator
Interactive tool: largest simultaneous AC load in, inverter size, DC current and battery cable fuse out.
What Size MPPT Charge Controller for Van Solar?
Calculate the MPPT amperage for your array: amps = watts ÷ volts × 1.25, rounded up. A 400 W array at 12V needs a 50 A controller.
What Size Inverter for a Camper Van or RV?
Size a camper inverter: continuous watts = largest simultaneous AC load × 1.25, plus surge headroom for motors. 1,000 W of load needs a 1,500 W inverter.
What Wire Gauge for the Battery-to-Inverter Cable?
Size the battery-to-inverter cable with ABYC 105°C ampacity and a 3% voltage-drop limit. A 1,000 W inverter at 5 ft needs 4 AWG and a 125 A fuse.
Which standard these numbers come from
Cable sizing on this site follows ABYC E-11 105 °C ampacity, which is the correct reference for 12/24V DC vehicle and marine wiring — not the household NEC table, which gives different and generally thinner results. Voltage drop is checked on the round-trip length at a 3% limit, and the thicker of the two answers wins. Fuses are sized to protect the cable, and every positive run is fused at its source.
Sizing the bank these components feed is covered under batteries, and the reasoning behind each formula is on the about page.