What size inverter do I need to run a fridge off-grid?

Looking at putting a proper fridge in our shepherds hut and need to sort the inverter situation.

Currently running a modest 48V setup with Victron gear, but honestly not sure what size inverter I'd need. The fridge is a fairly standard chest freezer (planning to use it as a fridge tbh), reckons about 150W running but the startup surge will be mental.

My main concern is whether I'm looking at a 3000W pure sine wave jobbie or if something smaller would do. The hut's only got solar and a small battery bank at the moment, so I'm wary of undersizing and killing everything when the compressor kicks in.

Also wondering if there's a way to calculate this properly? Like what's the actual inrush current on domestic fridges? I've seen some people mention soft starters but that might be overkill for a shepherds hut setup.

Would prefer to stick with Victron if possible — got their stuff dialled in already. Fogstar did some smaller inverters but not sure if they're still in stock.

Anyone running similar setups? What's your experience been with startup loads on your battery banks?

Right, mate — fridges are the sneaky power vampires of off-grid living. Everyone thinks "oh it's just a fridge" and then watches their battery bank collapse like a sack of potatoes.

The real answer depends on which fridge though. A proper 12V compressor unit? Totally different beast to a standard domestic one. I learned this

Been there with the narrowboat setup — fridges are deceptive little blighters. The thing most people miss is the startup surge, not the running watts.

Your 48V Victron system's a decent foundation, but here's what caught me out: a standard compressor fridge pulls maybe 150W running, but the initial kick when the compressor fires up can demand 800-1000W for a split second. If you're undersized, your inverter'll just cut out and you'll be left with warm milk and frustration.

For a shepherds hut, I'd honestly suggest minimum 3000W pure sine wave — gives you breathing room for other loads (kettle, tools) without the fridge triggering shutdowns. If budget's tight, 2000W works if that's all you're running simultaneously, but it's wearing a tightrope.

What's your battery capacity at the moment? And are you planning any other heavy loads alongside it?

Mate, the real kicker is that modern fridges pull a nasty inrush current when the compressor kicks in — you'll need roughly double what the nameplate says just for startup. Your 48V setup is decent, but I'd be looking at a minimum 3kW inverter, 5kW if you want to run anything else simultaneously (kettle, toaster, etc.).

Check what your fridge actually draws — look for the compressor specs, not just the average consumption figure. A 12V leisure fridge will play nicer with your battery bank than trying to run a full-size mains one. I've got a Fogstar 75L in my static caravan and it barely dents my battery vs. the grief a full-size caused before. Save yourself the headache and the inverter cost.

Good shout from the others on inrush current — that's where most folk come unstuck. Here's what I've learned the hard way with my motorhome setup:

The actual running wattage is only half the story. A typical fridge compressor pulls 3-5x its rated power on startup. So if your fridge is 150W continuous, you're looking at 450-750W surge for a split second.

I'd honestly recommend a 3000W minimum inverter for peace of mind with a decent-sized fridge. Sounds overkill, but you want headroom when the compressor kicks in alongside anything else running.

More importantly though — what type of fridge are you considering? Absorption (gas), compressor, or one of those 12V DC units? That changes everything. A proper 12V compressor fridge from Fogstar or Dometic would let you skip the inverter altogether and run direct from your 48V bank. Dead efficient.

What's your battery capacity looking like?

Got a fridge in my tiny house setup, so bit of real-world here — the inrush spike is mental. Compressor kicks in and you're looking at 3-4x the running draw for a few seconds.

With your 48V Victron system, I'd go minimum 3kW inverter to be safe. Running a standard fridge (around 150-200W continuous) sounds easy until that compressor fires up — then you're spiking to 600-800W+.

Worth noting: fridge duty cycle means it's not constantly drawing power anyway. Mine runs maybe 8-10 hours a day depending on ambient. Pair it with a decent battery buffer (your 48V helps here) and you're golden.

If cash is tight, a 2.5kW Victron Multiplus gets away with it, but you'll be nail-biting every time the compressor starts. 3kW gives proper headroom and you can run other bits without stress.

Right, the inrush spike is the killer — everyone focuses on running watts and forgets about the startup surge. Compressor'll pull 3-4x its steady-state draw for a split second.

I'd say minimum 3kW inverter for a standard fridge, realistically 4-5kW if you've got other stuff running. Your 48V Victron setup can handle it — pair it with a proper Victron inverter/charger and you're golden. The MPPT'll manage your charge nicely too.

Biggest thing though — check your battery capacity. A fridge cycles constantly, even in cold conditions. You'll want decent battery reserve or you'll be running your gen constantly just to top up. I learned that the hard way.

What's your current battery bank looking like? That'll make or break whether this actually works long-term.

The inrush thing is absolutely crucial — you lot have nailed it. I've got a Fogstar fridge in my narrowboat and learned this the hard way. The compressor pulls a massive surge when it kicks in, easily 3-4x the running wattage.

Running watts might be 150-200W, but you're looking at 600W+ inrush. Most folk size for running watts and wonder why their Victron inverter keeps shutting down.

For a 48V setup, I'd honestly go 3000W minimum if you're running other stuff simultaneously (lights, kettle, etc.). The headroom prevents nuisance shutdowns and protects your battery bank from voltage sag.

What's your actual battery capacity? That matters too — a small battery bank will sag under inrush even with a beefy inverter, which confuses the protection circuit. Size the inverter oversized, not undersized.

The inrush spike is genuinely the issue here, not the running load. Fridges pull 3-5x their running wattage when the compressor kicks in — so a 150W fridge needs a 5kW+ inverter to handle the surge without browning out your system.

I've got a 48V Victron setup in my static caravan and learned this the hard way. Went with a 5kW Victron MultiPlus because I wanted headroom for other loads. Could've skimped on a 3kW, but you'd be cutting it fine if anything else draws power simultaneously.

Worth checking your fridge's actual inrush spec from the manual if you can get it — some modern efficient models are better behaved than older ones. Also consider whether you're running other kit at the same time (kettle, shower, etc.). If it's just the fridge, you could go smaller, but reality is messier than the spec sheet suggests.

What's your current battery capacity? That affects how hard the inverter has to work too.

You've hit on the real issue — I've been there with my narrowboat setup. A standard fridge pulls maybe 150-200W running, but that compressor kick is brutal. You're looking at 800-1000W inrush depending on the model.

So here's what I'd actually spec: if your 48V system can handle it, grab a 3000W pure sine inverter minimum. Sounds overkill for a fridge, but you'll want headroom for other loads anyway (kettle, tools, etc.), and that surge protection matters more than the continuous rating.

The real trick is soft-start devices — Victron do a couple options that'll help tame the inrush. Worth the investment if you're on a tight battery budget.

@GazAllen — what's your battery capacity like? That'll actually be the limiting factor. A 3kW inverter is only useful if your batteries can actually support that spike without tanking the voltage. If you're running modest capacity, you might need to be more selective about which fridge model you choose — some RV units have gentler compressors than traditional

The inrush thing is real — I learned this the hard way with my motorhome setup. Had a 2kW inverter that should've been plenty for a 150W fridge, but it kept tripping the Victron breaker every time the compressor kicked in.

What sorted it: went to a 3kW pure sine inverter. Overkill on paper, but you need that headroom for the startup surge. If you're already running 48V Victron gear, a Victron MultiPlus 48/3000 would slot straight in and play nicely with your existing system.

One thing worth considering though — what else are you running simultaneously? If it's just the fridge in the shepherd's hut, even a 3kW might be oversized. But if you're running lights, a kettle, tools etc., you'll want the capacity anyway.

Also check your battery bank can actually supply that inrush current. A weak battery will cause more grief than an undersized inverter. What are you working with on the DC side?

Right, the inrush is definitely the killer here. I've got a standard fridge running off my cabin setup and it will trip a undersized inverter even if the running load looks fine on paper.

What sorted it for me was going 3kW minimum — sounds overkill for a 150W fridge but you need that headroom for the compressor startup. The Victron MultiPlus range is brilliant for this because it handles the surge better than cheaper units.

One thing worth checking: if your fridge is old or a cheap model, inrush can spike even higher. Newer A+++ fridges are gentler on the system. Also matters whether you're running anything else simultaneously — kettle goes on at the same time, you're asking for trouble.

What voltage are you working with? And is it a new fridge or something already kicking about?

The inrush spike is genuinely brutal — I've watched a 3kW Victron nearly catch fire trying to start a cheap fridge from Currys. The compressor draws 4-5x running current when it kicks in, sometimes spiking to 600-800W for those first couple of seconds.

What @SmartSolar_Master and the others haven't mentioned: soft starters make a real difference. I retrofitted one to my van conversion fridge and it absolutely transformed things. Cost about £40 and brought that inrush down from 700W to around 250W. Not perfect, but manageable.

For a shepherds hut with a modest 48V setup, I'd honestly suggest going 5kW minimum if you've got the budget and battery capacity — gives you headroom for other loads kicking in simultaneously. But if that's overkill, a decent soft starter on a 3kW inverter will get you most of the way there.

Which fridge are you actually looking at? Some of the newer ones (especially compressor models designed for off-grid) are much kinder on startup current than bog-

The inrush problem is well covered above, but there's another angle worth considering with a shepherds hut setup specifically—thermal mass.

Rather than oversizing the inverter (which gets expensive and inefficient), look at what you're actually running. A modern A++ fridge draws maybe 100-150W continuous, but that startup spike can hit 800W+ for several seconds. You need an inverter rated for sustained load plus at least 3x the running wattage for inrush headroom. So realistically, a 3kW Victron Multiplus would be the minimum I'd spec.

But here's the thing—in a shepherds hut, you've got decent passive cooling potential. Consider positioning the fridge away from south-facing walls and ensure decent ventilation around the back. In winter especially, you could actually dial down the thermostat and let the ambient temperature do half the work. I've found this cuts runtime by 30-40%, which takes real pressure off your inverter.

If your battery bank is modest, a DC fridge (like the Fogstar or Waeco units) might be worth exploring

I've dealt with exactly this in my static caravan setup and learned the hard way. The inrush spike is genuinely nasty — a standard fridge can pull 5-7x its running wattage when the compressor kicks in, which is why @GrumpyBuilder and @DriftWizard are bang on about that.

What I'd add though: have you considered a smaller, purpose-built 12V or 24V fridge instead? Something like a Fogstar or similar compressor model draws maybe 40-50A running but the inrush is far more manageable. I switched from trying to run a standard fridge and it's been miles better for battery stability.

If you're set on a conventional fridge, you're realistically looking at a 5kW+ Victron to handle the spike safely without tripping. That's a lot of battery capacity to support though.

What's your current battery bank size? That might be the limiting factor anyway — even if the inverter handles the inrush, the voltage sag under load will trash a smaller system. Worth doing the maths on total Ah before spending on a