Power and electricity on a sailing yacht: what a remote worker needs to know

Short answer: yes, you can keep a laptop, a phone and a second screen charged all week, and no, you will not be the reason the batteries run flat. But a boat is not a building, and the ten minutes it takes to understand where its electricity comes from will save you the one genuinely avoidable frustration of the week — discovering at 22:00 that the sockets are dead.

A boat is a battery, not a building

Every boat has two separate battery systems: a small start battery whose only job is turning the engine over, and a much larger house bank that runs everything else. Guests only ever interact with the house bank. On a typical cruising catamaran that is 400–600 Ah at 12 V — call it 5–7 kWh nominal. How much of that you can actually use depends on the chemistry: traditional lead-acid banks are damaged if drawn below about half, while lithium banks can be run much closer to empty, which is why newer boats feel far more relaxed about power.

For comparison, a UK household uses roughly 8 kWh a day. A boat runs eight people on less than that, which tells you most of what you need to know: nothing here is unlimited, but nothing here is scarce either, provided the big loads are managed.

Where the power actually comes from

Notice how well that lines up with the working day. The boat sits at anchor all morning running on solar while you work, then motors or sails in the afternoon, which recharges the bank — so by evening you are back near full. The rhythm is not an accident.

What everything on board actually draws

This is the table that resets people's expectations, because almost everyone assumes their laptop is a significant load. It is not.

Add it up: eight remote workers together draw roughly what the fridge does. The loads that actually decide whether a boat has power are the fridge, the satellite dish, and the watermaker if one is fitted — none of which are yours to manage. Which is the point of showing you the numbers: so you stop rationing your laptop and start asking the one useful question, which is when the inverter runs.

Why the inverter goes off at night

The 230 V sockets on a boat are usually fed by an inverter, which converts 12 V battery power up to mains voltage. Inverters draw a little power simply by being switched on, and they make it very easy for someone to plug in something enormous without thinking. So the normal convention is that the inverter runs during the day and is switched off overnight, protecting the bank for the fridge and the instruments.

That convention is not a rule imposed on you, and it is not fixed. If you genuinely need mains power at 23:00 for a call with another timezone, say so in the morning and the captain will plan for it — by leaving the inverter on, by taking a marina berth that night, or by running the engine for a while. It is a planning question, not a technical one, and the only wrong move is discovering the problem at 22:55.

The twenty per cent you throw away without noticing

Here is the one piece of genuine efficiency advice. Your laptop charger takes mains voltage and converts it back down to low-voltage DC. On a boat, that means the chain runs 12 V battery → inverter → 230 V → charger → roughly 20 V DC. Each conversion costs energy, and the round trip typically throws away something like a fifth of what you drew.

A USB-C Power Delivery charger that plugs straight into a 12 V socket skips the whole detour. It is a small, cheap item, it works when the inverter is off, and it is the single most useful thing in a remote worker's bag after a wired headset. Bring a long cable too — the 12 V sockets are never where the saloon table is.

What this means for your working day

• Charge during the morning block and the afternoon passage, when solar and the alternator are both contributing.
• Treat a marina night as the time to run anything heavy — big uploads, device charging, the things you have been putting off.
• Keep a 20,000 mAh power bank charged as your buffer. It covers a full working day and removes the question entirely.
• Screen brightness is your largest personal variable. Working in the shaded saloon rather than in glare on deck saves real battery, on your laptop and on the boat.
• If your laptop only charges from a 230 V brick, you are dependent on the inverter schedule. Check before you fly, not after.

Three questions to ask on the first morning

1. Where are the 12 V sockets, and where are the 230 V ones?
2. When does the inverter run, and when is it switched off?
3. Is there anything you would rather I did not plug in?

Thirty seconds of conversation, and the entire subject is closed for the week.

What not to bring

• Anything with a heating element. Kettles, hair dryers, travel irons and portable heaters draw enormous current and are the classic way to trip a boat's system.
• A desktop machine or a workstation-class laptop that only charges from a high-wattage mains brick.
• Multi-socket extension blocks with surge protection — some interact badly with inverter output. A simple one is fine if you ask first.
• Anything you would be upset to lose to a voltage spike. Boat electrical systems are robust but they are not a data centre.