What size solar panels for my off-grid cabin?

Been through this exact scenario with my own van conversion—the roof weight anxiety is real, but there's a practical middle ground most folks miss.

Instead of cramming panels onto a questionable roof, consider a split setup: 2-3kW of fixed panels on a ground mount or shed, paired with 1-2kW on the van roof itself. Spreads the load, gives you flexibility if you need to relocate, and honestly performs better since you can angle the ground array seasonally.

For a 24ft static, you're looking at needing roughly 4-6kWh daily in winter if you want reliable autonomy. That's achievable with modest rooftop capacity plus external mounting. I run a Victron MPPT controller with mix of Renogy and some older Fogstar panels—the controller doesn't care where they're mounted, just that the strings are properly configured.

@TID_Electric's spot on about the 240-280kg figure. Don't guess—actually measure your caravan's specification sheet or ring the manufacturer. Some statics have reinforced sections, others are basically glorified tin boxes.

What's your battery bank looking like currently?

Go lightweight and split it across the roof—I've got 400W of thin-film panels on my motorhome and they weigh about half what monocrystalline would, plus they handle partial shade better when you're parked under trees (which you will be, trust me).

Skip the roof entirely if you're static though. Ground mount or a simple frame you can angle seasonally—costs less, keeps your roof warranty intact, and you won't spend three years wondering if that creaking sound means imminent disaster. Pair it with a decent MPPT like a Victron SmartSolar and you'll be sorted regardless of how cloudy it gets.

What's your battery capacity looking like? That matters more than panel size anyway—no point having 2kW of panels if you've only got 5kWh storage.

Got a shepherd's hut so slightly different setup, but the roof weight thing is legit worth taking seriously. Static caravan roofs aren't designed like house roofs.

What I did was go for quality over quantity — three 400W Victron panels rather than loads of cheap ones. Spread the load better and you're not punching holes everywhere. My hut's got a proper timber frame so I could handle it, but on a caravan you're looking at aluminium extrusions mostly.

@RetiredNurse49's got the right idea with thin-film if your roof's dodgy. They're genuinely lighter and perform okay in cloudy UK weather (actually better than mono in low light). Downside is they're less efficient, so you'll need more space.

Real talk though — get a structural survey done first. Sounds daft but it's the difference between a safe install and an expensive mistake. Most caravan repairs places can tell you what your roof will take. Then size your battery setup around what you can actually fit, not the other way round.

What's your daily usage looking like? That'll narrow things down properly.

Right, I'll throw in the cautionary tale nobody wants to hear. Had a mate with a static who thought "what's the worst that could happen?" Turns out, a lot—particularly when December rain decided his roof's structural integrity was negotiable.

The thing is, @BayTim, your setup's actually got a massive advantage over us boat dwellers. You're

Depends entirely on your actual consumption, mate. What's your daily usage looking like? Are you running heating, cooking electric, or just lights and a laptop?

For a static you've got the luxury of roof space that motorhome folks don't, so weight distribution is less of a headache than @RetiredNurse49 suggests—though still worth calculating. I'd lean toward standard mono panels (330-400W each) rather than thin-film; better efficiency per square metre and they handle UK winter better.

Rule of thumb: aim for 1.5–2x your average daily consumption in peak winter conditions. So if you're using 10kWh/day, you'd want 15–20kWh of generation capacity accounting for poor sunlight and angle loss.

Also factor in your battery bank size. No point having 2kW of panels if your battery only accepts 500W charge rate. What battery setup are you considering? That'll determine whether you need a Victron MPPT or multiple controllers.

Static caravans can handle serious weight—check your chassis specs and distribute panels across both sides if you can. Balances the load

Before you settle on a size, have you calculated your winter vs summer needs? Statics are notorious for heat loss, so if you're planning year-round off-grid living, you might need considerably more panels than summer calculations suggest. What's your battery capacity looking like? That'll really dictate your minimum panel wattage.

You're spot on that statics are thermal sieves. I'd push back on guessing—measure your actual draw for a fortnight first. Caravan leisure batteries vary wildly in capacity too. Once you've got those numbers, work backwards: daily consumption → battery bank size → solar array (accounting for British winter irradiance, which is grim). What's your battery setup currently?

Spot on what @Titch says—measure first, guessing'll cost you. I went same route with my shepherd's hut, thought I knew what I needed. Winter draw was nearly double my summer estimate. Once you've got proper figures, aim for 40-50% excess capacity. Victron MPPT controller will maximise whatever you throw at it. What's your battery bank looking like?

Mate, everyone's right about measuring first. What I'd add—check your panel placement on the caravan roof. Shadows from roof vents and aerials killed my charging in winter. Might be worth tilting a separate array on the ground instead. Victron MPPT controller will squeeze every watt out of whatever you install.

@BayTim Good call starting here. Once you've got your consumption figures sorted (as @Titch and @BatteryTim rightly said), factor in your location's winter sun angle—that'll really dictate panel count. Also worth checking if your caravan roof can handle the weight. What's your rough monthly kWh target looking like?

Have you considered seasonal variation? I'm in a motorhome and winter consumption versus summer is massive for me. Panel output drops significantly November-February even down south. Work out your worst-case month figures rather than averaging annual usage. What's your battery capacity looking like? That'll inform whether you can get away with smaller panels if you've got decent storage to buffer poor weather days.

Worth checking if you can mount panels at an angle rather than flat on the roof - makes a massive difference for winter generation in the UK. I've got mine on adjustable brackets on the boat and it's honestly a game-changer. Victron mppt controller too if budget allows, handles wonky angles better than cheaper units.

@BayTim the angle thing @BoatLouise mentions is critical for winter. I'd aim for 45-50° if possible on a caravan. Rule of thumb: size for winter worst-case, not summer. What's your battery capacity? That'll dictate panel size more than roof space usually does. Once you know how many kWh you need daily in December, we can work backwards.