How Much Solar Do I Need for a Campervan? A Practical Sizing Guide

The most common question we get from van owners is also the simplest sounding: how much solar do I actually need? The honest answer is that it depends on what you run — but working it out takes ten minutes with a piece of paper. Here is the method we use when customers ask us to size their systems.

Step 1: Add up your daily usage

List everything electrical in the van and estimate how many hours a day you use it. Multiply each item's wattage by its hours to get watt-hours (Wh). Typical figures for a weekend camper:

LED lighting (10W, 4 hours) = 40Wh. Phone and tablet charging = 30Wh. Compressor fridge (45W, running about a third of the time) = 350Wh. Water pump and odds and ends = 30Wh. Diesel heater fan on cold nights = 50Wh. That is roughly 500Wh per day — a realistic baseline for a van with a fridge. Without a fridge, most people land nearer 150Wh.

Step 2: Factor in UK sun

A solar panel only delivers its rated wattage in perfect conditions. In the UK, a rule of thumb that works well in practice: expect about 4 effective sun hours a day in summer, 2.5 in spring and autumn, and 1 or less in December. A 100W panel therefore gives you roughly 400Wh a day in July but perhaps 100Wh in winter.

To cover 500Wh a day from spring to autumn, you want around 150–200W of solar. For summer-only weekends with no fridge, 80–100W is plenty. For full-time living with a fridge, laptop and inverter, plan for 250–350W plus a healthy battery bank.

Step 3: Match the kit to your van

For battery maintenance and light use, a 20W kit with crocodile clips keeps a leisure or starter battery topped up between trips for under £70.

For weekend campers, an 80W or 100W lightweight folding kit with MPPT controller needs no permanent installation — unfold it at camp, point it at the sun, pack it away when you leave. The 120W folding kit adds headroom for a compressor fridge in summer.

For permanent roof installations, our 180W and 210W semi-flexible kits with self-adhesive backing bond directly to the roof — no drilling, almost no added height, and enough output for off-grid living three seasons of the year.

Don't skimp on the controller

An MPPT controller harvests up to 30% more than a basic PWM unit, and the gap is biggest exactly when you need it — overcast days and low winter sun. If you are building your own system rather than buying a kit, something like the Victron SmartSolar MPPT 75/10 pairs with panels up to 145W and shows live output on your phone via Bluetooth. Add a battery monitor shunt and you will always know exactly how much power you have left — the single best upgrade for avoiding flat-battery surprises.

Quick reference

Battery maintenance only: 20W. Weekend trips, no fridge: 80–100W. Weekends with a fridge: 120–160W. Extended trips, three seasons: 180–250W. Full-time living: 250W+, ideally with a lithium battery bank.

Every van is different — roof space, battery chemistry and how you camp all change the answer. Send us your appliance list and we will size the system for you, free, before you spend a penny. Or browse the full range of ready-to-install solar kits.