Solar power in a camper van: sizing, wiring and monitoring

Electrical independence in a van comes down to three choices: how much solar, which battery, and how well you can see what is going on.

A converted van is a small self-sufficient house: solar production, storage, water, heating. Here is how to size the electrics — and above all how to stay in control once you are on the road.

Step 1: your daily energy budget

List what draws power, in Wh per day. Realistic benchmarks:

• Compressor fridge: 400 to 600 Wh a day (the biggest single item)
• LED lighting: 30 to 60 Wh a day
• Charging phones and a laptop: 60 to 150 Wh a day
• Water pump and ventilation: 30 to 80 Wh a day
• Diesel heater (ignition plus blower): 100 to 300 Wh a day in winter

A comfortable setup typically comes to 700 to 1,200 Wh a day.

Step 2: the solar to match

A van roof does not behave like a house roof: the panels lie flat (roughly 15% less yield), there is shading, and the seasons bite. The field rule: 1 Wp of panel produces 2 to 4 Wh a day depending on the season in France.

• Summer and shoulder-season use: 300 to 400 Wp is enough
• Four-season use: 400 to 600 Wp — and accept that in December solar will not cover everything (driving and a DC-DC booster take over)

Step 3: the battery, heart of the system

LiFePO4 has won: two to three times lighter than lead for the same usable capacity, thousands of cycles, deep discharge without damage. Sizing: two to three days of autonomy without sun, which means 200 to 300 Ah at 12 V for a budget of 1,000 Wh a day. Choose a battery with a communicating BMS (Bluetooth, such as a JK-BMS): you will see the real state of each cell.

Step 4: the blind spot — monitoring

This is THE weakness of van installations: every device has ITS own app. A Victron app for the solar, another for the BMS, nothing for the water, nothing for the heater — and the nagging "how much is left?" in the middle of a drive.

The right architecture is a single dashboard that brings it all together — solar, battery, water tanks, temperatures, CO2, GPS — and that works without internet (out in the wild, the cloud does not follow). That is exactly what we built with the heliolocal Van Dashboard: a 7-inch touchscreen that reads Victron solar and the battery BMS over Bluetooth, watches fresh and grey water levels, and controls lighting and pumps — fully local, and viewable from home over a VPN.

The three mistakes we see constantly

• Oversized panel, undersized battery: the midday excess has nowhere to go; balance the two
• Undersized wiring: at 12 V the currents are high — be generous with cable cross-sections and fuse every circuit
• No monitoring at all: you discover the battery is flat exactly when you need it

Let us talk about your van

Every conversion is different: request a quote for a Van Dashboard matched to your setup (Victron, JKBMS, a compatible heater), or write to us — we are happy to answer technical questions, with or without a purchase.