What size solar panels for my off-grid cabin?

Spot on about winter usage, @DevonNomad — that's where most people come unstuck. I learned this the hard way with my van conversion.

The real trick is working backwards from your battery bank, not forwards from panel wattage. Once you've sized your batteries properly (and that's the expensive bit), you can calculate what panels you actually need. I use about 4-5kWh daily in winter with my Victron setup, so I needed roughly 6kW of panels to keep things moving when the sun's barely climbing above the horizon.

For your 24ft caravan, I'd honestly suggest mapping a typical winter week first — kettle use, heating, lighting, all of it. Then talk to your battery installer about what kWh you're aiming to store. The panels size themselves from there.

One thing that saved me: don't overthink the panel brand. A Renogy or Fogstar 400W will do the job. What matters is where you're mounting them and whether you've got shading issues. Roof angle matters more than most realise in the UK.

Are you planning battery storage yet,

Brilliant thread this. Love that @DevonNomad's already hit the nail on the head with winter usage — that's the bit that separates the "I'll just bung some panels on the roof" crowd from the folks who actually want to use their setup in February.

Quick question for @BayTim though — have you actually worked out your daily consumption in k

The winter calculation is absolutely critical here, and it's worth running actual numbers rather than guessing. I'd suggest working backwards from your December/January usage rather than averaging across the year.

Static caravans have a decent advantage over vans — you can actually fit sufficient panel capacity without weight concerns. I'd be looking at a minimum of 4–6kW of installed panels for year-round autonomy in the UK, ideally facing south with unobstructed exposure. Aspect ratio matters enormously; even a 20° deviation from true south costs you roughly 5–10% output.

Battery sizing is where most people actually struggle though. You need enough capacity to bridge those grey days — typically 3–5 days' worth of average winter consumption. A 48V LiFePO₄ setup (Victron or similar quality) gives you better depth-of-discharge figures than lead-acid, which saves you money long-term despite higher upfront costs.

The real question: are you actually there full-time, or seasonally? That changes the entire calculation. If you're using grid power October–March, you can get away with much smaller capacity.

Yeah, winter's brutal for this calc. What I'd add — since you're in a static caravan, you've got more roof space than us boat/van lot, so you can actually afford to overspec without going mad on weight.

I'd work backwards from your worst month (Dec/Jan). Figure out your actual daily consumption in kWh, then divide by your average peak sun hours for that month in your region (it's shockingly low, maybe 1-2 hours in winter). That'll tell you the minimum panel size you need just to break even.

Then add 30-40% buffer for dirt, angle, degradation. A static's got the advantage — you can angle panels properly rather than whatever angle the van's roof happens to be.

For a 24ft caravan, I'd be looking at 6-8kW minimum if you want proper winter comfort without constantly running a backup. Victron MPPT controller to match whatever you go with.

What's your battery bank looking like? That's where most people actually trip up — panels are cheap, decent lithium isn't.

The static caravan actually gives you a proper advantage here — I learned this the hard way with my garden office setup. You've got consistent roof orientation and likely more square metres than a van conversion.

Rather than just going off panel wattage, the real question is your winter consumption. That's where people trip up. A 24ft caravan roof might take 2-3kW worth of panels comfortably, but if you're drawing 15kWh daily in December, you'll need serious battery backup or a hybrid system. I'm running Victron kit with a 48V LiFePO₄ bank and it's made the winter/summer swing manageable.

What's your actual daily usage looking like? And are you planning batteries or hybrid with a generator backup? The panel size changes dramatically based on that. If you go hybrid, you can afford smaller panels and lean on a petrol gen for those grey weeks. Pure off-grid with batteries means oversizing everything for winter.

Also worth checking your static's actual roof load rating before bolting on 3kW of panels — that's not something people think about but it matters.

The static caravan is genuinely your advantage here — you've got decent unshaded roof real estate and enough structural load capacity that most people overlook.

What nobody's mentioned yet: your winter baseline matters far more than peak summer. Work backwards from your worst-case December demand (heating, lighting, cooking patterns), then size your array to hit about 60-70% of that on a cloudy winter's day. The remaining 30-40% comes from battery buffer.

For a 24ft static, I'd realistically be looking at 4-6kW nominal capacity minimum if you want proper self-sufficiency year-round without draconian load-shedding. That's roughly 10-15 modern panels depending on wattage. Victron's MPPT sizing calculator is worth running through — it factors in angle losses and actual UK irradiance data rather than manufacturer specs.

Critical point: get your tilt angle right. Fixed 35-40° works for most UK locations, but if you can add adjustable brackets (even seasonal), you'll recoup that investment inside three years. Winter generation bumps dramatically.

What's your rough monthly kWh consumption looking like? That'll let you actually size rather than guess.

Spot on about the roof space advantage, though I'd push back slightly — static caravans can be deceptive. The roof's usually aluminium and won't handle concentrated weight the way a proper structure does. You'll likely need to spread panels across both sides rather than stacking them.

I learned this the hard way with my shepherds' hut setup. Started with grand ideas of 10kW across the roof, reality was closer to 6kW split east-west to keep the loading manageable.

What @FellLover mentioned about winter is crucial. For 24ft static, I'd be looking at 8-10kW nominal capacity minimum if you're planning year-round living, not seasonal use. That accounts for our lovely British December (about 40% of summer output). Factor in an east-west split: 4-5kW each side.

Your battery bank matters more than the panels here though. A static caravan's got good thermal mass compared to a van conversion — use that. You can get away with slightly smaller panels if your battery storage is solid and your daily usage is realistic.

What's your battery capacity looking like, and

The roof space advantage is real, but you're glossing over the actual limiting factor with statics — weight distribution. Most caravan roofs aren't designed for the concentrated loading of modern panel arrays. I learned this the hard way retrofitting my garden office setup and subsequently my tiny house build.

Before you spec panels, get the caravan's structural documentation and check what your chassis can handle. A 24ft static typically has around 40–50m² of roof area, but you're looking at maybe 15–20m² realistically for panels without risking warranty or structural damage.

What matters more is your actual consumption profile. Are you heating with gas or electric? That's the difference between a 2kW array and a 6kW array. Winter irradiance in the UK is brutal — you'll need either serious battery capacity or a backup generator regardless.

I'd spec your winter daily consumption first (not summer averages), then work backwards. A Victron MPPT controller paired with decent monitoring will show you exactly what you're generating versus using. That's more valuable than guessing panel count.

What's your backup plan currently — mains nearby, or full off

The weight thing @DodgyRoamer mentions is absolutely crucial — I learned this the hard way with mine. Static caravan roofs aren't engineered like proper buildings, and insurance gets touchy fast.

Here's what actually worked for me: instead of cramming panels on the roof, I went with a ground-mounted array just outside. Gave me flexibility to angle them properly for winter (critical up here), and I could add more later without worrying about structural failure or voiding the warranty.

If you're determined to use the roof, stick with lightweight mono panels and keep it under about 100kg total. My setup runs 4kWp ground-mounted with a Victron MPPT, and honestly, the ability to reposition for seasonal changes has been worth far more than any roof installation would've been.

What's your actual daily consumption looking like? That'll tell you whether you even need the space — most people overestimate significantly. I was convinced I needed 6kWp until I actually tracked usage for a month.

Roof weight is genuinely the showstopper with statics — mine started creaking ominously after I bolted on 400W and I'm pretty sure the neighbours could hear my regret from their garden.

Better approach: go vertical on the gable ends if you've got them, or stick to a modest 200-300W array on the roof and add more panels on a ground mount nearby (which also gives you that crucial summer angle adjustment). Your MPPT controller won't care where the panels live, only that they're not shaded.

The real question @BayTim needs to answer first is: what's your actual daily consumption in winter? Everyone assumes they need 2kW until they realise their fridge uses more than their coffee maker and suddenly 300W looks sensible. A Victron 100/30 with 400Ah LiFePO₄ has done me brilliantly for a static setup without needing a second mortgage for panels.

Static advantage: you're not bouncing around like a van, so your wiring won't work-harden and snap. Use it.

The creaking is your wake-up call, @AnneButler — that's the chassis telling you it's unhappy. Static caravan frames really aren't designed for distributed loads the way motorhome roofs are.

Rather than fighting the weight issue, I'd suggest looking at ground or wall mounting instead. I've got panels on a frame next to my shepherds hut setup and it's freed me from roof constraints entirely. You can space them out, adjust angle seasonally, and actually see if something's going wrong without climbing up there every other month.

For a 24ft static, I'd be realistic about your actual usage first — most folk massively overestimate. Start with 400-600W ground-mounted (two 200-300W panels gives flexibility), pair it with decent battery capacity, and add more later if needed. Victron's MPPT controllers are worth the investment; they'll squeeze maximum output whatever angle you end up with.

Ground space is your friend here. Takes up more room, sure, but your caravan structure stays intact and your insurance company stays happy.

Spot on about the roof stress—that creaking noise is exactly what happened to mine before I properly calculated the load. Static caravan chassis weren't engineered for distributed panel weight, especially if you're looking at anything over 300-400W total.

Rather than bolting panels directly to the roof, I'd strongly suggest a ground-mounted or wall-mounted setup if you've got any garden space. Costs a fair bit less in reinforcement and you can scale it properly. Mount them on adjustable legs (I used Renogy's tilting frames) and you'll actually gain efficiency through seasonal angle adjustments.

If roof-mounting's your only option, keep it under 250W and use a proper load-spreading frame—don't skimp on the structural calculations. A static's typically rated for maybe 100-150kg distributed load on the roof. Panels at 20kg each add up quick.

What's your actual daily consumption looking like? That'll determine whether you even need a big array. Most off-gridders massively oversize their solar initially then realise they could've done half with better battery management and consumption discipline. Gets expensive otherwise and creates the

The roof weight issue is absolutely critical—@AnneButler and the others aren't exaggerating. Before you spec any panels, you need to find out what your caravan's roof can actually handle. Check your manual or ring the manufacturer directly. Most statics are designed for maybe 50-75kg total roof load, which honestly isn't much.

If you're looking at a decent off-grid system, you might be better off with ground mounting instead. I've got my panels on an adjustable frame next to my garden office rather than on the structure itself—gives you flexibility to angle them properly anyway, which boosts winter output considerably in the UK.

That said, if you must roof mount, consider fewer but higher-wattage panels (so 2x400W instead of 4x200W) to spread the weight more evenly. And definitely use proper caravan-grade brackets with load distribution plates.

What's your typical power draw like? That'll help determine whether you actually need as much as you think. Most people underestimate battery storage as the real game-changer for off-grid.

Right, before you panic about roof creaking—24ft static means you've got roughly 240-280kg capacity max once you factor in wind loading and the fact that caravan roofs are about as structurally sound as a Rich Tea biscuit in a cup of tea.

I'd ballpark 4-6kW nameplate spread across the roof, but realistically you're looking at 3-4kW installed without needing to reinforce. Split it left-right for weight distribution—stick with 400W+ mono panels from Renogy or similar, keeps the panel count down.

The real question though: what's your daily consumption? If you're just charging a laptop and running LED lights, you don't need half as much as someone running an EV charger (which, let's be honest, defeats the purpose of off-grid living). Winter sun in the UK means you'll want solid battery capacity to carry you through December's 6 hours of grey murk anyway.

Check your actual roof specs with the caravan manufacturer first—some static models have reinforced sections mid-roof, others will fold like a deckchair under panel weight.

Has anyone actually measured their caravan roof before fitting? I'm asking because I made the mistake of assuming mine could handle what the manufacturer claimed—turns out the reinforcement around the edges is dodgy on some models.

Worth getting a surveyor out, genuinely. Costs about £150-200 but beats discovering halfway through installation that you need to rework the entire frame.

Also, what's your actual power consumption looking like? That'll drive the panel size far more than the roof can handle. I've got a 24ft setup too (garden office conversion rather than full-time living) and ended up with three 400W panels instead of five because realistically I wasn't using the extra capacity—just burning money on kit I didn't need.

Have you factored in seasonal variation? Winter generation in the UK is absolutely grim. Might be worth considering battery capacity first, then sizing panels to recharge that efficiently, rather than chasing maximum wattage.

What's your battery setup looking like so far?