How Many Solar Panels Do You Need for a Campervan?

"Just put 200W on the roof" is the advice everyone gives — and it's wrong as often as it's right. The number of solar panels your campervan needs depends on three things you can actually measure: how much energy you use, how much sun you get, and how big your battery is. This guide turns those into a single formula, then a sizing table you can read off in seconds.

1. Start from your daily consumption

Solar is sized to refill what you take out, so you have to know your daily draw first. For each appliance, multiply its power in watts by the hours you use it per day to get watt-hours (Wh), then add them up. If you have not done this yet, our companion guide on calculating campervan battery autonomy walks through it step by step.

A typical two-person van lands around 800 Wh/day: a compressor fridge, LED lights, a roof fan, a water pump and charging a couple of phones and a laptop. Heavy users with an induction hob, a coffee machine or Starlink can easily double that.

2. Know your peak-sun-hours

A 100W panel almost never makes 100W. What matters is peak-sun-hours (PSH) — the number of hours per day equivalent to full 1000 W/m² sun. It bundles latitude, season and weather into one number.

3. The solar sizing formula

To find the panel wattage that replaces your daily draw, divide consumption by your peak-sun-hours, then divide by ~0.75 to account for real-world losses (MPPT conversion, heat, panel angle and partial shade).

Worked example with our 800 Wh/day van, sizing for a conservative 4 sun-hours:

The same van in Southern Europe summer (5.5 sun-hours) only needs 800 ÷ 5.5 ÷ 0.75 ≈ 194 Wp — so 200W is genuinely enough there, then. That gap is exactly why a single "right answer" doesn't exist.

4. Sizing table by use case

If you'd rather not run the maths, read your row off this table. It assumes lithium storage and ~4 conservative sun-hours.

When in doubt, round up a panel size. Extra solar is cheap insurance against cloudy weeks, and a DC-DC alternator charger covers the rest while you drive.

5. Match panels to your battery

Panels and battery are a pair: too little battery and you waste midday sun you can't store; too little solar and you never refill. A widely used balance is roughly 100Ah of lithium per 200W of solar.

So 300W pairs naturally with ~150–200Ah, and 400W with ~200Ah. Lead-acid (AGM/GEL) only lets you use ~50% of its capacity, so you need roughly double the nameplate Ah to store the same usable energy.

6. Rigid vs flexible panels

For most vans, rigid panels win on cost-per-watt and longevity. A folding portable panel is a smart add-on: park the van in shade and put the panel in the sun.

Common mistakes

• Sizing for summer only. Winter peak-sun-hours can be a third of summer's — size for your worst travel month.
• Ignoring panel losses. Always apply the ~0.75 factor; nameplate watts are lab numbers.
• Too much solar, too little battery. You can't store what you can't hold — keep the ~100Ah / 200W balance.
• Forgetting shade. One shaded cell can cripple a whole rigid panel; an MPPT controller and good placement matter.
• Counting on the alternator alone. A DC-DC charger helps while driving, but solar is what keeps you stationary off-grid.