Ask this question in any van forum and you’ll get ten confident answers that all contradict each other. One person swears a single panel changed their life, another insists you need the roof covered to survive a weekend, and somewhere in the middle sits the truth, which is that they’re all right for their own situation and none of them are answering yours. The amount of solar you need isn’t a fixed number you can borrow from a stranger. It depends entirely on how you travel, what you run, and when you go.
That’s frustrating if you were hoping for a single figure to buy and be done with, but it’s also good news, because it means you can work out your own answer with a bit of straightforward thinking rather than guessing or overspending. The goal here isn’t to hand you a number, it’s to show you how to find yours, so you fit a system that suits the way you actually use your van instead of the way someone on the internet uses theirs.
Start With What You Use, Not What You Buy
The mistake nearly everyone makes is starting with the panel. They ask how many watts they should buy before they’ve worked out what they’re trying to power, which is backwards. The right starting point is your daily consumption, meaning an honest tally of the electrical things you use in a normal day and roughly how much they draw. Your lights, the water pump, phone and laptop charging, and above all the fridge if you run one, all add up to a daily figure that represents what you need to put back in.
The fridge is usually the big one, since it runs on and off around the clock and quietly accounts for a large share of many vans’ consumption, so it’s worth paying particular attention to. Once you’ve added everything up, you have a rough daily energy figure, and that number is the foundation of the entire decision. Everything that follows, panel size, battery size, all of it, exists to service that figure. Skip this step and you’re just buying a size that sounds reassuring, which is how people end up with either far too little or money spent on capacity they never touch.
How Much Power a Panel Actually Gives You
The next thing to understand is that a panel’s rated wattage is not what you get out of it in real life, and this trips up a lot of first-time buyers. That number is measured under ideal laboratory conditions, and the British climate is not an ideal laboratory. What a panel actually generates over a day depends on how many hours of decent light it gets, the angle of the sun, cloud cover, and the season, and those variables swing enormously here.
The seasonal difference is the part people most underestimate. A panel that comfortably keeps you topped up through long, bright summer days will produce a fraction of that on a short, grey December afternoon, sometimes only a quarter or less of its summer output. This matters because it means your solar needs are really defined by when you travel. If you’re a fair-weather, summer-months camper, the sums are gentle and forgiving. If you intend to be out in winter, you need to plan around those short dark days rather than the flattering summer figures, which usually means considerably more capacity to achieve the same result.
Matching Panels to How You Travel
This is where your honest travel style turns into an actual system size. A weekend camper who heads out mostly in the warmer months, runs lights and charges a few devices, and doesn’t rely heavily on a power-hungry fridge needs surprisingly little, and a modest setup will keep them going comfortably. Someone spending longer stretches off-grid, running a fridge continuously and working from the van, sits in a different bracket entirely and needs meaningfully more generation to stay ahead of their consumption. And the full-time or winter traveller is in a different world again, planning around the worst-case dark days rather than the easy ones.
The sensible approach is to choose a campervan solar panel setup scaled to your genuine pattern of use rather than to an aspirational one or a worst-case fantasy. Be realistic about how you actually travel, not how you imagine you might one day, because the light user who buys for a full-time winter scenario wastes money, while the heavy user who buys for gentle summer weekends ends up flat and frustrated. Match the system to the real you, allowing a bit of headroom for the days that are cloudier or busier than average, and you’ll land close to right. The three broad camps, occasional summer use, regular longer trips, and serious off-grid or winter living, each call for genuinely different amounts, so knowing which one you’re in is most of the answer.
The Rest of the System Matters Too
It’s tempting to treat this as purely a panel question, but solar only works as part of a system, and panels are just the generating half of it. What you generate has to go somewhere, and that somewhere is your leisure battery, so battery capacity matters just as much as panel wattage. There’s little point fitting generous panels if you haven’t the storage to hold a day’s worth of power, since anything you generate beyond what the battery can take is simply lost. Equally, a big battery with too little panel to fill it will sit half-empty and leave you short.
Between the two sits the charge controller, which manages the power flowing from panels to battery safely and efficiently, and a decent one genuinely improves how much of your generation you actually keep. The takeaway is that these three parts have to be balanced against each other, sized to work as a whole rather than bought in isolation. Throwing money at panels while skimping on battery, or the reverse, gives you a lopsided system that underperforms what you paid for. When you plan, plan the whole thing together, because the balance between them is what determines whether the setup actually delivers day after day.
Working Out Your Own Number
So the way to answer the question is to build it up from your own facts rather than reach for a figure. Add up your realistic daily consumption, be honest about which season and travel style you’re planning for, and size your generation and storage together to comfortably meet that demand on a typical day, with a margin for the poorer ones. It’s a bit of arithmetic rather than a dark art, and doing it yourself gives you a system that fits instead of a guess that might not.
One closing piece of advice worth taking is to fit slightly more than your bare minimum if budget and roof space allow, and to leave room to expand later. Power needs have a habit of creeping up as you add a gadget here and spend longer off-grid there, and a little headroom now saves an awkward upgrade down the line. The people who are happiest with their solar are rarely the ones who bought the biggest system or the cheapest, but the ones who took an hour to work out what they actually needed and built sensibly around that. Do that, and you’ll travel with the quiet confidence of knowing your lights will still be on tomorrow, wherever you’ve chosen to wake up.