What gauge cable do I need for a 2000W inverter?

Been looking at upgrading my narrowboat setup and finally ready to pull the trigger on a proper 2000W inverter. Currently running a smaller 1000W unit and it's constantly throttling when I try to run the kettle + charging devices simultaneously.

Planning to install a Victron or similar quality unit, but I'm getting different answers on cable gauge from various sources. Some folks reckon 10mm² is overkill, others say you need it for anything over 1500W.

My specific situation:

• 24V lithium battery bank (LiFePO₄)
• Battery to inverter distance is about 2 metres with a slight bend
• Plan to install proper automotive-style connectors with tinned terminals
• Will be in an enclosed locker so ventilation isn't a major concern

Does anyone have experience with this setup on a boat? I want to avoid voltage drop issues and keep things safe — not keen on melted cables or a fire risk whilst we're moored up somewhere remote.

Should I go with 10mm² or would 6mm² suffice? Also, any recommendations on fusing? I've read contradictory guidance on whether to use a 200A or 300A ANL fuse, or if I should go with something different altogether.

Cheers for any input — this is all new territory for me and I'd rather get it right first time than bodge it and regret it later.

You'll want 6mm² minimum, ideally 10mm² if you've got the runs longer than a couple of metres. I learned this the hard way on my boat — undersized cable and you're looking at voltage drop that'll have your inverter cutting out or the cable getting warm.

What's your battery bank voltage? That matters quite a bit. I'm running 48V with a Victron MultiPlus 2000VA and went with 10mm² from battery to inverter (about 2 metres) and haven't had a single throttle issue since switching from my old 6mm² setup.

Also check what amperage your specific unit draws at full load — some 2000W inverters are more efficient than others. Are you thinking pure sine wave? Definitely worth it on a boat if you're powering sensitive electronics.

What battery capacity are you working with? Bit of context there might help refine the advice.

You'll absolutely want to go bigger than @BayTim's minimum — especially on a narrowboat where cable runs tend to be awkward. I've got a 2000W Victron on my array setup and learned the hard way that undersizing cable creates heat losses you can't afford.

What matters is your battery voltage and distance. At 12V, you're looking at serious current draw — over 160A at full load. I'd push for 10mm² as standard, 16mm² if your battery bank is more than 3-4 metres away from where the inverter sits.

The cost difference between 10 and 16mm² is minimal compared to voltage drop headaches. Undersized cable also stresses the inverter's input stage and kills efficiency right when you need it most.

What's your battery setup and how far's the run from batteries to inverter location?

The cable gauge really depends on your battery voltage and run length. What are you working with — 12V, 24V, 48V?

I've got a 3000W Victron on my motorhome running off 48V LiFePO4, and I used 16mm² for a 2-metre run from battery to inverter. Overkill perhaps, but voltage drop was negligible and it runs cool. On a narrowboat you're likely looking at tighter spaces though.

At 2000W on 12V you're drawing massive current — easily 160A+. Even short runs will drop voltage badly with undersized cable, which kills efficiency and stresses the inverter. On a boat where everything's squeezed in, heat dissipation's harder too.

Go with what @LiFePO4Nerd's saying — measure your actual run, then go one size up from the calculator recommendations. Cheap insurance against voltage sag when you're trying to run kettle + microwave simultaneously.

Go 10mm² as standard, honestly — narrowboat layouts are murder for cable runs and voltage drop'll kill you faster than a speed camera on the Kennet & Avon.

What voltage are you running? That's the real game-changer here. 12V on a 2kW inverter is basically asking for a sauna in your battery locker, whereas 48V keeps the amps sensible and cable costs reasonable.

I'm running a Victron 3kW on 48V with 16mm² and it's still warm to the touch during summer loads. Skip the penny-pinching on copper — you'll regret it when your motorhome's smelling of melted insulation and you're stuck without leccy.

What's your battery bank spec?

Mate, voltage drop is the real killer here. If you're going 12V from battery to inverter, even a short run can lose you critical amps with undersized cable.

What's your battery bank voltage and how far are we talking from battery to inverter? That'll determine whether you need 10mm² or go even bigger.

I've got a 2000W Victron on my setup at 24V with about 1.5m of cable, and I'm using 16mm² — probably overkill but the peace of mind's worth it. The difference in cost between 10mm² and 16mm² is negligible compared to voltage drop headaches or a fried inverter.

On a narrowboat the cable routing's always a nightmare too. Better to overspec slightly than find yourself having to pull everything out again.

The voltage drop calculations are crucial here, so let me break down what I've learned from my own caravan setup.

If you're running 12V (which I'd guess you are on a narrowboat), the current draw at full load will be around 166A. That's absolutely massive for cable sizing. @BodgeItAndScarper's right to ask about your battery voltage — 24V halves that current to 83A, which makes a real difference.

For a 12V system with any reasonable cable run (say 2-3 metres), you're looking at 16mm² minimum, ideally 25mm². Even then, you'll be pushing 3% voltage drop if you're unlucky. I ran the numbers on my Victron 3000W setup in the static caravan using 25mm² and still get about 0.3V drop — acceptable but noticeable under heavy load.

The real solution though? Go 24V if your narrowboat layout allows it. Halves your cable requirements, reduces heat loss, and your batteries will thank you for the lower current stress. I've seen too many forum posts

The cable gauge debate always comes down to your actual run length, which most folks don't measure properly. I ran 16mm² on my narrowboat because the battery bank sits 8 metres from the inverter location—sounds mad but a 2kW inverter pulls 160+ amps at 12V during startup, and voltage drop compounds quickly over that distance.

What @FormerCop and @AngliaOffGrid are spot on about: even "short" runs on a boat are deceptive. You're routing through lockers, under floorboards, around the engine bay. That's rarely the straight line you think it is.

My actual recommendation: measure your cable run wall-to-wall, then calculate voltage drop using this formula: (2 × length × current) ÷ (conductivity × cross-sectional area). Aim for under 3% drop. On a narrowboat pulling 160A at 12V, you'll likely need 10mm² minimum for runs over 3 metres, or 16mm² if you've got the space.

Also worth mentioning—use proper marine-grade tinned copper cable

Cheers for the detailed replies, @FormerMechanic14 and @Boycie. Just to add from my own boat experience — I went through this exact dilemma last year and ended up measuring my actual cable run three times because I kept getting different numbers the first go.

The thing I'd emphasise is whether you're running 12V or 24V makes a massive difference. I switched to 24V specifically to avoid the cable gauge nightmare on a 2000W load. If you're staying at 12V, you're probably looking at 35-50mm² depending on your run length, which gets pricey and unwieldy in tight boat spaces.

Also worth considering: are you running from a single battery or a bank? My setup uses a Victron MultiPlus 2000 on 24V from a parallel-connected battery setup, and it honestly made the cable routing cleaner.

What's your current battery configuration and how long is the actual run from batteries to inverter? That'll help narrow down whether upgrading cable is even the bottleneck versus your battery's discharge rate.

The voltage drop is the real killer here. I've got a 2000W Victron on my setup and learned this the hard way — went with undersized cable initially and the inverter was cutting out under load.

Quick rule of thumb: measure your actual cable run from battery to inverter. If it's under 1m, 16mm² might work, but honestly I'd go 25mm² to be safe. Anything over 1.5m and you're really looking at 35mm² to keep voltage drop under 3%.

Also consider your battery voltage. If you're 12V like me, the current draw is massive — around 167A at full load. That's where proper cable sizing makes the difference between smooth operation and the inverter constantly throttling like your current setup.

One more thing — make sure your DC breaker or DC switch is rated for that cable size. I see too many people sort the cables then use a tiny breaker. Defeats the purpose entirely.

What's your battery voltage and how far are we talking from battery to inverter?

Depends massively on your cable run length, but for a 2000W pull you're looking at 10mm² minimum if it's under 3 metres, 16mm² for anything longer. I made the mistake of undersizing on my boat initially — the voltage drop was noticeable and the inverter kept dipping out.

The thing most people miss is that 2000W at 12V is a lot of current — roughly 166A peak. Your battery cable needs to handle that comfortably without heating up. Victron's own sizing guide is worth a look if you're going their route.

Also worth noting: if you're on a boat like me, factor in the cable routing through tight spaces. Thinner gauge cables are tempting but you'll regret it when you're trying to squeeze 16mm² through existing conduit.

What's your actual battery-to-inverter distance?

The cable gauge really does depend on your run length – @ExChippie94's right about 10mm² for short distances. On my narrowboat I've got about 4 metres from battery to inverter and I'm running 16mm² because the voltage drop was becoming a proper issue at 2000W continuous draw.

What voltage are you working with? If it's 12V you'll need thicker cable than 24V for the same run. Use an online voltage drop calculator – aim for no more than 3% drop ideally, though 5% is often the practical compromise on boats where space is tight.

Also worth checking your battery's actual capacity to handle the surge current. A 2000W inverter pulling from a smaller battery bank can cause serious voltage sag, which then feeds back as inverter throttling regardless of cable size.

What's your current battery setup and approximate cable run? That'll make it easier to give you a definitive answer rather than guessing.

10mm² is your starting point but honestly, go 16mm² if you've got the budget — voltage drop at 2000W is brutal and every millivolt counts when you're trying to run the kettle and microwave simultaneously.

Cable run length matters most though. If you're measuring from battery to inverter in metres, calculate the voltage drop properly using an online calculator (there's a decent one on the Victron site). Anything over 2-3% and you'll watch your Victron throttle itself like a sulky teenager.

I've seen too many people on narrowboats and motorhomes cheap out on cable gauge, then wonder why their 2000W inverter only delivers 1500W. The battery terminals are usually the next weak point — make sure they're proper quality lugs, not the bargain bin ones from Halfords.

What's your actual battery-to-inverter distance? That'll tell us if you need to go heavier gauge or if you're overthinking it.

Mate, if you're running 2000W through anything longer than a sneeze, 10mm² will have your voltage sagging like a shepherd's hut roof in January. I went 16mm² on my cabin setup and the difference was genuinely noticeable — lights stayed bright, inverter less grumpy. The cable costs pennies compared to the Victron you'll be strapping to your batteries, so why cheap out? Also check your battery connectors whilst you're at it; seen too many people upgrade the cable then wonder why performance is still dodgy because the lugs are fit for a 1000W unit. What's your actual run length anyway?

Honestly, what's your actual cable run? That's the key bit everyone's dancing around.

I've got a 2000W Victron on my boat and learned the hard way — 10mm² works fine if you're talking under a meter, but anything longer and you're fighting voltage drop. I'm running 16mm² from my battery bank to the inverter (about 2.5m) and it made a proper difference to performance.

The real issue is the cost difference between 10mm² and 16mm² is minimal compared to losing efficiency. At 2000W you're pulling serious current, so voltage sag adds up quick.

What's your battery setup? If you're running 24V instead of 12V that changes the math a bit — lower current means smaller cable works better. Worth double-checking before you buy.