System design check — am I making a mistake?

Been piecing together a 5kW system for my static caravan and want to sanity-check before I commit the funds. Currently spec'd out:

• 16x 330W panels (Renogy, mixed orientation for winter generation)
• 10kWh LiFePO4 battery bank (considering Fogstar modules)
• 8kW Victron Multiplus II inverter/charger
• MPPT controller (leaning Victron 250/100)

The question that's nagging me: am I oversizing the inverter relative to my actual loads? My caravan's peak draw is probably 4-5kW (kettle + microwave), and realistically I'm not running both simultaneously. The Multiplus II at 8kW feels excessive, but I've read the efficiency curves flatten out significantly below rated capacity.

Also second-guessing the battery size. 10kWh sounds reasonable for a week of poor weather, but I'm wondering if I should drop to 8kWh and reinvest in another 2-3 panels instead. Would that actually improve my autonomy, or am I just spreading pounds too thin?

One more thing: I've got limited roof space (roughly 20m² usable), so those 16 panels are quite tight. Should I focus on maximising panel count or battery capacity for UK winter reliability?

Appreciate any reality checks from people running similar setups. Particularly interested if anyone's gone the "smaller battery, more panels" route and whether it's worked out practically.

Mixed orientation sounds like you're hedging your bets, but 16x 330W in a caravan setup is decent – just make sure your roof can handle the wind loading without turning into a sail. What's your battery capacity looking like? Because 5kW peak generation means sod all if you've only got 10kWh storage and you're burning through it by teatime. Also, are those panels actually going to see sunlight year-round, or is your caravan parked behind a wood where you get three hours of winter sun? I've got similar wattage on my shepherds hut and December is basically a theoretical exercise unless I'm supplementing with generator. Renogy panels are solid though, no complaints there.

Mixed orientation is a solid move for winter – you'll catch morning and afternoon sun better than a single south-facing array. 5.28kW nominal is plenty for a static caravan, assuming your battery bank can handle the charge rate.

What's your inverter spec and battery capacity? That's where most people stumble. I've got a similar setup on my cabin and found a Victron MultiPlus handles the mixed input better than cheaper units – the MPPT controllers just work harder but cope fine.

One thing: make sure your wiring runs can handle the current from 16 panels. Easy to under-spec that bit. What batteries are you going with? LiFePO₄ or lead?

Mixed orientation definitely makes sense for a static setup – you're not tilting panels seasonally like we boat folk do, so spread works better.

What's your battery capacity though? That's where most caravan builds fall short. 5kW peak sounds good on paper, but if you've only got 10-15kWh storage, you'll be throttling the inverter half the time waiting for sun or running the backup gen constantly.

Also worth checking: what's your winter usage looking like? Caravan demand tends to spike (heating, hot water) exactly when panels underperform. I'd rather see you spec'd for 70-80% winter self-sufficiency than chase that optimistic summer rating.

What battery setup are you considering? LiFePO₄ or lead-acid?

Mixed orientation is sound logic, but I'd challenge the panel count slightly. 16x330W gives you 5.28kW nominal, which is decent, but in a static caravan you're constrained by roof space and mounting. Have you actually measured your available roof area? I've seen folk spec optimistically then realise they can't physically fit the panels without shading issues.

More critical question: what's your battery capacity and inverter spec? A 5kW array needs proper buffering—I'd expect at least 10-15kWh usable storage for a caravan, otherwise you're just dumping excess generation in summer. And if you're using a standard hybrid inverter, make sure it's rated for split-phase or single-phase properly.

What battery chemistry are you leaning toward? That'll shape your charge controller requirements too.

The mixed orientation is sensible for static caravan use – you'll genuinely see better winter output than purist south-facing. That said, @Titch's point about oversizing is worth considering from a different angle.

5.28kW nominal sounds good on paper, but what's your charge controller rated for? If you're running a single MPPT (say, 150V Victron), you could hit voltage limits on a clear winter day with that many panels in series. You might need two controllers, which adds cost and complexity.

Also – what battery capacity are you planning? 16 panels generating well is only half the equation. If you've got undersized storage, you'll be curtailing generation on good days, which defeats the purpose of the mixed orientation investment.

What's your battery spec looking like?

Mixed orientation works, but the real question is what battery capacity you're planning. That 5.28kW array will hammer a undersized bank in summer and leave you struggling in winter — classic boom-bust scenario.

For a static caravan you've got options the boat folk don't. If you're grid-connected or have backup gen, you can size the battery for daily cycles rather than multi-day autonomy. Cuts costs significantly.

What's your expected daily usage and how many days autonomy are you targeting? That'll dictate whether you need a chunky lithium setup or can get away with a smaller system that tops up regularly.

Also worth checking — roof loading limits on the caravan. 16 panels is decent weight to verify.

What's your battery capacity looking like? That's where this gets real. I've got a similar setup feeding a shepherd's hut (south-facing panels mainly, but I regret not mixing angles more for winter), and the limiting factor was always the battery, not the array.

5.28kW sounds decent on paper, but static caravans pull constant ancillary loads – fridges, heating circuits, that sort of thing. If your battery's undersized, you'll either be grid-tied (defeats the purpose) or cycling the panels hard in marginal light trying to keep up.

How many days of autonomy are you designing for? Winter generation in the UK is genuinely grim. Mixed orientation helps, sure, but at 5kW you're still fighting uphill December through February unless you've got serious kWh storage behind it.

Also – what's your inverter spec? Make sure it can actually handle that array without derating. A Victron or Fronius unit will give you better visibility into what's actually happening, which matters more than it sounds once you're living off it.

The battery question is absolutely crucial here. I learned this the hard way with my own emergency backup setup – spec'd the panels first, then realised the batteries were the real bottleneck.

Your 5.28kW array will generate brilliant midday peaks, but a static caravan typically has a more predictable load pattern than off-grid homes. What matters is: how many hours of autonomy do you actually need? Winter days are short, and your mixed orientation only helps so much in December.

I'd suggest working backwards from your worst-case scenario. If you're running heating, cooker, and basic lighting in January with minimal daylight hours, you need serious storage to bridge those gaps – we're talking 10-15kWh minimum for comfortable winter use, more if you want genuine resilience.

The Victron BMV units are brilliant for understanding your actual consumption patterns before you buy the batteries. Might sound like extra expense, but it's genuinely the difference between a system that works and one that frustrates you all winter.

What's your current battery spec looking like? That'll tell us if you're properly matched or heading for a bottleneck.

Mate, everyone's dancing around it but they're right — you've got a cracking array there but without knowing your battery size it's like asking if a fire hose is enough without mentioning the bucket.

5.28kW of panels is brilliant for winter generation with that mixed orientation, but come summer you'll be throttling the inverter constantly if your battery bank can't absorb the midday peaks. I learned this the hard way with my motorhome — oversized panels + undersized batteries = expensive charge controller watching the sky.

What's your actual kWh spec? And equally important: what's your daily consumption looking like? A static caravan's got different demands than my van (I can live like a caveman; folk in caravans want proper living).

Once you drop those numbers we can actually tell if you're golden or if you need to rebalance. Victron kit can handle whatever you throw at it, but the maths needs to work first.

The panel spec looks solid for a static setup, but I'd push back on the mixed orientation thing slightly — unless you're genuinely getting shaded differently across seasons, you might be spreading your generation too thin. Worth calculating your actual winter vs summer yield for your postcode.

What I'm really curious about though: are you planning to run this year-round or just seasonal? That changes everything for battery sizing. I've got a motorhome with a Victron system and the difference between "winter caravan weekends" and "full-time off-grid" is night and day in terms of how you spec the battery bank.

Also — is that 5kW the inverter size or your daily usage target? Because @MarshLover and the others have nailed it: those panels are only half the puzzle. If you're undersized on batteries, you'll either be running a generator constantly or dumping generation in summer.

What's your expected daily consumption looking like? That'll tell you whether you need 10kWh, 20kWh, or something else entirely.

Mixed orientation's a pain to wire up and you'll get less overall efficiency than a single tilt optimised for winter. Static caravan means you're not moving it about, yeah? Just bite the bullet and angle everything south at your latitude.

The real question though is what battery capacity you're running. 5kW of panels without enough storage is like having a Ferrari with a milk float's fuel tank. On a static setup you've got the space for proper lithium or a chunky LiFePO₄ bank. Don't cheap out here.

Also worth considering: are you tied to grid or fully off-grid? Makes a massive difference to your design. If you're still grid-connected, a smaller battery with a good hybrid inverter (Victron Multiplus or similar) gives you way more flexibility than over-speccing battery for independence you might not need.

What's your typical winter consumption looking like? That's what'll actually dictate whether 5kW of panels is overkill or undersized.

The mixed orientation thing — yeah, I've been there. Done it on my old static setup and honestly it's more hassle than it's worth. You end up with uneven panel strings, potential mismatch losses, and when one string's in shade the whole thing suffers.

What worked better for me was accepting that winter generation will never match summer, then sizing the battery and inverter to handle that reality rather than chasing panels to do it all. A single south-facing array at around 35° gives you decent year-round performance without the wiring nightmare.

5kW sounds right for your needs, but @EdHamilton you've not mentioned the battery size yet — that's the real limiter on a static caravan. Are you looking at lithium or lead-acid? If it's a smaller system (say, 10-15kWh) then you might find that winter generation bottleneck bites harder than you expect, regardless of panel layout.

Worth running some actual winter day figures through a simulator before you commit. The weather data for your location makes a real difference.

Depends what you mean by "mixed orientation" really. If you're talking east/west split, yeah, that's what I've got on my motorhome and it's genuinely useful — smooths out generation through the day rather than getting hammered at noon then nothing. Wiring's not that messy if you plan it properly with a decent combiner box.

But if you mean random angles all over the place, @GrumpySparky's right — waste of time.

Main thing I'd ask: what's your battery capacity and usage pattern? 5kW of panels is decent, but if you're drawing power at night you'll still need decent storage. Winter generation's tricky in the UK no matter what you do. I found my Victron MPPT actually helps squeeze more out in poor conditions than optimising angle ever did.

What battery setup are you looking at?

Worth asking what you mean by "mixed orientation" first — the lads above have got different interpretations running.

If it's east/west split, you're trading peak output for flatter generation across the day. That works for caravans where you're actually using power throughout daylight rather than just midday. I've got something similar on my shepherds hut and it suits the load profile.

However, if you're mixing tilt angles and orientations on the same strings, that's where efficiency really takes a hit. You'll get mismatch losses and the panels will be fighting each other in terms of voltage.

5kW nominal is ambitious for a static caravan — what's your battery capacity and what loads are we talking about? The panels are only half the equation. A properly sized MPPT controller (Victron or equivalent) will help squeeze the most out of whatever orientation you settle on, but it can't magic around fundamental mismatch.

What's your winter generation target actually based on?