Solar panel for a campervan: the complete guide

Setting off for several days without plugging your campervan into a hook-up, keeping the fridge cold and the phones charged in the middle of nowhere: that is exactly what a solar panel on the roof makes possible. But before buying the first kit you come across, you need to understand one thing: campervan solar has nothing to do with house solar. Here we are off-grid, at 12 volts, with a battery to recharge — not a grid-connected system that sells back its surplus. This guide gives you the method to size a reliable on-the-road system.

Off-grid: a logic of its own

On a house, the panels produce 230 V, the system is connected to the electricity grid and you talk about self-consumption and grants. On a campervan, none of that applies: the panel charges a 12 V battery, and it is this battery that powers your appliances, wherever you are. No connection, no feed-in — the sole objective is autonomy.

This difference changes everything about your choice of equipment. There is no point chasing maximum power: what matters is the balance between what the panel produces during the day and what you consume over 24 hours, by way of the battery. If your goal is instead to produce for your home, you should look towards residential photovoltaics — an entirely different logic.

How much power do you need?

It all starts with your daily consumption, expressed in watt-hours (Wh). Add up what each appliance uses per day: that total is what your system will have to replace.

Estimating your daily consumption

A few realistic ballpark figures for a campervan:

• LED lighting: 5 to 15 Wh per day
• Water pump: 5 to 10 Wh per day
• Charging phones / tablet: 20 to 40 Wh per day
• 12 V compressor fridge: 200 to 400 Wh per day (the biggest item, by far)
• TV / laptop: 50 to 150 Wh per day

Light weekend use often comes to around 150 to 300 Wh/day; living year-round with a compressor fridge quickly climbs to 400-700 Wh/day.

Translating that consumption into panel watts

In Belgium and Western Europe, a well-oriented panel produces on average 3 to 4 Wh per watt-peak per day over the year (more in summer, far less in December). A 100 W panel therefore delivers, roughly, 300 to 400 Wh on a fine day, and markedly less under overcast skies.

The practical rule: aim for a panel power that covers your daily consumption even in average weather, then size the battery to last one or two days without sun.

The four components of a system

A campervan solar system always rests on the same quartet. Every link counts — a good panel held back by a poor controller is wasted energy.

The panel

It captures the sun and produces direct current. Its power (in watt-peak) determines what you can recover each day. You choose its type — rigid or flexible — according to the roof (see below).

The MPPT controller

A key piece, often underestimated. It matches the panel’s voltage to the battery’s and protects it against overcharging. Prefer an MPPT controller over a PWM model: it recovers 20 to 30% more energy, especially in cold or hazy conditions — exactly the Belgian situation.

The 12 V lithium battery

This is what stores and releases the energy. A lithium (LiFePO4) battery discharges to 80-90% without damage, lasts 2,000 to 3,000 cycles and weighs half as much as an AGM. A 100 Ah lithium offers ≈ 1,000-1,100 Wh genuinely usable, versus 500-600 Wh for an AGM of identical nominal capacity.

The inverter

Optional but handy: it turns the battery’s 12 V into 230 V so you can plug in household appliances (coffee maker, laptop charger). Size it for the most power-hungry appliance, and bear in mind that 230 V drains fast: restraint remains your best ally when running off-grid.

Rigid panel, flexible, or complete kit?

The choice of panel depends mostly on your roof and how you use it.

For most campervans with a flat, rigid roof, the rigid panel on spacers remains the best choice: the air gap beneath the panel cools it, which maintains its efficiency (a hot panel produces less). The flexible type is reserved for domed roofs, over-cab beds or converted vans where every kilo counts.

Roof installation: the key points

Installation happens in two stages: the mechanical mounting on the roof, then the wiring to the battery.

• Fixing: the rigid type is screwed or glued onto supports (spacers); the flexible one is glued directly. In both cases, good sealing mastic is essential so you don’t pierce the roof’s waterproofing.
• Watertight roof gland: the cables go down through a dedicated, sealed cable gland, never through an improvised opening.
• Cable cross-section: respect the recommended cross-section (often 4 to 6 mm²) to limit losses between the panel and the controller.
• Controller location: as close to the battery as possible, in a ventilated and accessible spot.

Careful installation makes all the difference over time: failed sealing is paid for in leaks, and undersized wiring in lost watts.

Calculating your real autonomy

Autonomy is the number of days you can hold out without sun, on the battery alone. The calculation is simple:

Autonomy (days) = usable battery energy (Wh) ÷ daily consumption (Wh).

A concrete example: a 100 Ah lithium battery delivers around 1,050 usable Wh. With a consumption of 350 Wh/day (fridge + lighting + charging), that gives ≈ 3 days of autonomy with no solar input at all. As soon as the panel produces, that counter recharges: in fine weather, 200 W of panel comfortably covers those 350 daily Wh and even recharges the battery.

The real question, then, is not “how many panel watts?” but “what balance between panel and battery?”: the panel for production on sunny days, the battery to get through grey days and nights.

The 30-second recap

Guide verified in May 2026 · updated every year