Narrowboat inverter keeps tripping on the washing machine – 12v or 24v system worth upgrading?

Been through exactly this with a static setup but the principle is the same — washing machines are notorious for their startup surge. The motor inrush can hit 3-5x the running wattage for a split second, and most budget inverters simply can't handle it even if they're "rated" for the load.

12v vs 24v is worth thinking about carefully here:

• At 12v you're pulling massive current for any serious load — cable losses and connector resistance become a real problem on a boat where runs can be long
• 24v halves your current for the same wattage, which means less voltage sag under surge conditions — this alone can stop the tripping
• 48v is obviously overkill for a narrowboat unless you're running a serious solar array

What inverter are you currently running and what's its peak/surge rating? That's the first question. A cheap 2000w unit with 4000w surge is very different from a Victron MultiPlus which handles surge far more gracefully and has proper soft-start support built in.

Also worth considering — some washing machines (Bosch compact units are popular on boats) have a lower startup surge than others. Might be worth looking at the machine itself, not just the inverter.

What's your battery bank situation? If you've got significant internal resistance (older lead-acid, poorly balanced cells), voltage sag under surge will make the problem worse regardless of system voltage.

Anyone else running appliances successfully on 12v narrowboat setups? Curious what inverter brands have worked well in the marine environment specifically.

@BatteryDaz good point on the inrush — worth adding that the inverter's continuous wattage rating is almost meaningless for this application. What matters is the surge/peak rating, and even then some cheaper units can't sustain it long enough for the motor to spin up properly.

For what it's worth, I had similar grief powering tools in my garden office. Switching to a 24v system made a noticeable difference — shorter cable runs, lower current, and the Victron Multiplus I ended up with handles surge loads far more confidently than my old 12v unit did.

On a narrowboat I'd honestly lean toward 24v if you're rewiring anyway. Has the OP checked whether their current inverter even has a published surge rating, or just a continuous one? Some budget units are vague about that spec deliberately.

@Bomber makes a fair point but I'd push back slightly — continuous rating does matter once you're past the surge.

The real issue on a 12v system is the cable run. A 2000w inverter at 12v is pulling ~170A at peak. Volt drop over even a short run is brutal, and that's often what's causing the trip rather than the inverter itself hitting its limit.

Going to 24v halves those currents immediately. Made a massive difference on my cabin setup — same Victron MultiPlus, same loads, far less grief.

If the boat's already wired 12v throughout, a full system swap is painful. But if you're only running the inverter at 12v and the rest is 12v DC loads, a 24v inverter with a DC-DC converter for the 12v stuff is worth considering.

@BatteryDaz this is exactly what pushed me toward upgrading my shepherd's hut system to 24v — and honestly it was one of those decisions where I wish I'd just done it from day one rather than faff about with undersized kit first.

On a boat specifically though, has anyone actually run the numbers on what gauge cable you'd need to carry that surge current at 12v vs 24v? Because halving the current at 24v isn't just a theoretical win — it's the difference between cable runs that are practical on a narrowboat and ones that require you to gut half the interior to fit properly.

Also genuinely curious — is anyone running a Victron Multiplus on their boat for this exact reason? The soft-start assist feature seems like it'd be a game changer for washing machine surge without needing to upsize everything dramatically.

@StormyWelder same story with my garden office setup — went 24v and the difference on surge loads was night and day.

One thing nobody's mentioned yet: cable losses. On 12v you're pushing double the current for the same wattage, so your cables and connections are working much harder. On a narrowboat where runs can be long and space is tight, that heat buildup is a real concern.

Also worth looking at your inverter brand. Some cheaper units have quite pessimistic surge ratings. My Victron handles washing machine inrush without blinking — the surge tolerance on their spec sheets tends to be honest rather than marketing fluff.

If upgrading the whole system feels too much right now, a softstart device on the washing machine inlet buys you time and is dead cheap comparatively.