What Size Solar Panel Kit Do You Need for a Campervan or Motorhome?

If you're planning a campervan or motorhome solar setup, the most common question is simple: how many watts do you actually need? The honest answer depends on what you're running and how much sun you'll realistically get, but there's a straightforward way to work it out.

Step 1: Add up your daily power use

List every 12V appliance you run and how many hours a day you use it, then convert to watt-hours (Wh) per day:

• Compressor fridge: roughly 40-60Wh per hour of active cooling, often 400-700Wh/day depending on ambient temperature
• LED lighting: 5-10W per light, a few hours a day is usually under 100Wh/day
• Water pump: short bursts, typically under 50Wh/day
• Phone/laptop charging: 20-100Wh/day depending on devices
• 12V-to-230V inverter loads (if fitted) can add significantly more — check the wattage of whatever you plug in

Add these up for a rough daily total. A modest van setup (fridge, lights, charging) often lands somewhere between 500Wh and 1,200Wh per day.

Step 2: Work out how much solar that needs

A solar panel's rated wattage is its output in perfect, direct sunlight. In real UK/European conditions — with cloud, panel angle, and roof shading factored in — a panel realistically produces somewhere in the range of 2.5-4 usable "sun hours" worth of its rated output per day outside peak summer.

As a working rule: divide your daily Wh need by 3 to get a sensible panel wattage target. So 900Wh/day of use suggests aiming for roughly 300W of solar. This is a starting point, not a guarantee — cloudy days and short winter daylight will always undercut it, which is why most systems are sized with a buffer rather than to the exact minimum.

Step 3: Match the panel to the battery

Solar panels charge a battery bank, they don't power appliances directly. If your battery is too small, excess solar output on a sunny day is wasted; if it's too large relative to your panel, it may rarely reach full charge. As a rough guide, a 100Ah 12V lithium battery pairs comfortably with 100-200W of solar for typical daily-use cycling, while larger setups (200Ah+, higher daily loads) suit 300W and up, often split across two panels for better shading tolerance.

Rigid vs flexible vs folding panels

For van and motorhome roofs, rigid framed panels are the most efficient per watt and the longest-lasting, but need proper mounting brackets and add roof height. Semi-flexible panels sit almost flush and suit curved or low-profile roofs, though they typically run slightly warmer (and therefore marginally less efficient) without an air gap underneath. Folding/portable kits are worth considering if you want to chase the sun by positioning the panel away from the vehicle, or if you don't want a permanent roof fixture at all.

A few practical starting points

• Weekend use, minimal appliances: 100-150W kit with a small controller
• Regular touring, fridge + lighting + charging: 200-300W
• Full-time living, higher loads, inverter use: 300-400W+, often across two panels

Frequently asked questions

Will solar alone keep my leisure battery topped up in winter?

Not reliably on its own — short daylight hours and low sun angle in UK winter can cut solar output significantly. Most full-time van dwellers pair solar with a mains hook-up or DC-DC charger from the vehicle alternator as a backup for winter months.

Do I need an MPPT or a PWM controller?

MPPT controllers are more efficient, particularly when panel voltage is higher than battery voltage, and are the better choice for most modern setups. PWM controllers cost less and are perfectly adequate for smaller, well-matched systems. See our separate guide on MPPT vs PWM controllers for the full comparison.

Can I oversize the panel beyond what my controller can handle?

No — check your controller's maximum input current and voltage rating before adding panels, especially if wiring panels in series. Exceeding it can damage the controller.

Still not sure what you need? Get in touch with Solarika and tell us what you're powering — we'll help you size the right kit.