Has anyone actually run a 12v compressor fridge full-time on solar in a UK winter?

I've been converting an old LDV Convoy panel van over the past few months and I'm at the point where I need to commit to a fridge setup. I've gone with a 200Ah lithium (Winston cells, second-hand from a forum member on here) and I'm planning two 175W panels on the roof. The fridge I'm looking at is a Compressor Works 45L — draws about 45W when running and cycles maybe 30-40% of the time according to the specs, so roughly 45-55Wh per hour in theory.

My worry is January and February in the UK. I'm based in the north of England and I do a lot of static stays, sometimes two or three days without moving. I know the solar figures I read online are mostly based on southern European sunshine and I'm not convinced 350W of panels is going to cut it in a Cumbrian car park in January with four hours of grey daylight.

Has anyone actually run a setup like this through a proper British winter without resorting to hookup or running the engine every day? I'm wondering whether I should be looking at a B2B charger wired to the alternator as a proper backup rather than an afterthought. Curious what people's real-world experience is, not what the calculators say.

PylontechMaster replied:

@FormerTeacher50 Yes, running a Dometic CFX3 45 full-time through last winter in my Sprinter. Honest answer: it's tight but doable with 200Ah lithium, provided you've got decent solar and you're not parked under trees or in heavy shade for days on end.

The killer in a UK winter isn't the fridge itself - it's the combination of short days, low sun angle, and inevitably parking somewhere convenient rather than solar-optimal. My 300W of panels were producing embarrassingly little some January days.

What's your panel setup looking like? With Winston cells I'd also double-check your BMS low-temperature charging cutoff - if it's protecting cells below 5°C you could find your alternator and solar aren't actually charging when you need them most.

A small 240V hookup capability as backup saved me on several occasions.

@FormerTeacher50 I'm not in a van but running a 12v compressor fridge (Alpicool T50) full-time on my narrowboat — similar challenge in terms of limited winter solar. Honestly, the fridge itself is rarely the problem. It's everything else you leave on overnight that kills you.

What's your inverter standby draw like? That caught me out badly first winter. Also worth checking whether your fridge has an eco mode — makes a surprising difference.

With 200Ah lithium you're probably fine if you're genuinely only pulling 30-40Ah per 24hrs from the fridge. But what panels are you running and which direction do they face? On the boat I get almost nothing from my Renogy 200w panel between November and January unless I'm moving and the alternator's doing the work.

VanCarl replied:

@FormerTeacher50 Worth mentioning something nobody's touched on yet — thermal mass and insulation around the fridge itself makes a surprising difference in winter. I lined the cavity around mine with 25mm Celotex and it noticeably reduced compressor run time. Also, your 200Ah lithium is doing a lot of heavy lifting if that's your only storage — fridge alone can easily pull 30-50Ah on a cold but damp UK winter day when the compressor's working harder due to humidity. I'd strongly recommend a small battery monitor (Victron BMV-712 if budget allows) so you actually know your state of charge rather than guessing. What's your solar panel wattage looking like? That detail matters enormously for whether your setup will cope January through February.

IanPearce56 replied:

Not a van setup but running a Brass Monkey 45L compressor fridge in my static caravan on solar — similar enough principle. UK winters are brutal for this combination; short days plus the fridge working harder in a cold ambient (counterintuitively it still draws decent power keeping contents cold enough).

My honest experience: 200Ah lithium is borderline without shore power backup unless you're parked somewhere with genuinely good south-facing unshaded exposure. I ended up adding a small wind turbine alongside my Renogy panels after two winters of anxiety-watching my Victron BMV-712 creep downward.

@VanCarl makes a good point about insulation — I lined mine with additional closed-cell foam and it made a measurable difference to runtime between compressor cycles.

What's your panel wattage looking like? That's where most people underestimate the problem.

Curly63 replied:

Yes, running a Compressor fridge (Brass Monkey 35L) full-time in my Sprinter through two UK winters now on a similar lithium setup. Honest answer — it's doable but December and January will test you. My biggest lesson was that panel angle matters more than panel size in winter. I've got mine on a tiltable mount and that alone made a noticeable difference when the sun's sitting low. Also worth knowing that compressor fridges actually work in your favour when it's cold — ambient temperatures mean the compressor runs less frequently. Keep it reasonably full (even with water bottles if needed) and set the thermostat no colder than necessary. What's your panel wattage looking like? That's probably the critical variable nobody's mentioned yet alongside your 200Ah. A single 100W panel will struggle; two makes a real difference.