Narrowboat electrics is a complicated and complex subject due to the different systems involved. All narrow boats have a slightly different set up depending on equipment and whether shoreline power is available.

Electrical switch board on a narrowboat
Narrow boat electrics control panel

Electrics… Terminology

Here is a brief definition of some of the narrowboat electrical terms we refer to within the Electrics section:


This is a unit of electric current. It is a physical count of how many electrons are flowing down a cable. Amps cannot be lost or damaged, for example if 5 amps left a battery; 5 amps would return to the battery.


This is the ‘push’ to force the electrons to flow around the wires. It’s this push that gets used up when electricity does work, so whenever work is done the voltage gets used up or drops. Voltage drop can be an issue on canal boats and narrowboats.


This is the most common measurement used on domestic appliances and most readily available on product descriptions and packaging, for example a 2000 watts hairdryer or 750 watts microwave will describe how hot a microwave will be. It is important to understand the wattage of any appliances you wish to use on board a canal boat or narrowboat and whether your power system can support it.

Volts, amps and watts are linked by the following formula:

  • Watts = Volts x Amps


  • Watts divided by Volts = Amps

If something reduces the voltage, typically volt drop, less current will flow so less electrical power is available and appliances may not work to their full potential.

DC and AC

Electrical current from batteries and alternators always flows positive to negative by convention. In AC (alternating current) the current flow constantly reverses direction. This enables high voltages to be sent longer distances. This is the basis for domestic electricity supply.


This is a measure of resistance, therefore restricts current flow. For example a low wattage bulb will only allow a small current flow.

Amp Hour

This indicates how much electricity a battery will hold. A 110 ah (amp hour) battery is theoretically capable of supplying 110 amps for one hour.

Electrics… A Brief Explanation!

The most important things to understand about electricity are that unless you respect it, it can cause fire or even kill you.

We expect all users of The FitOutPontoon will be sensible, level headed individuals so please excuse us for pointing out the obvious.

We also appreciate that a little knowledge can be a dangerous thing and the benefit of a professional will be that it is their livelihood that is at stake if they get it wrong. We do cover some theory in this site, and where possible we will give guidance based on sound principles. For example, we explain how to correctly size wiring and to work out current loads. Aside from that, we recommend your narrowboat electrical work is entrusted to the most competent person you can find.

That may be you, so if you’re not a qualified marine electrician there are some very good basic electrical courses available that are specifically aimed at the narrow boat market. Anyone who has a passing interest in the subject could do a lot worse than enrolling on a day or two course. A good course will teach you by classroom theory as well as practical application. You will learn not only about DC circuits for the leisure system but also about DC in the engine room.

Unfortunately, many older narrowboats suffer from poor quality fiddling, where accessories have been added to wiring systems that are barely able to cope. The biggest problem with canal boat electrics are that they are for the most part hidden away behind paneling.

Your Boat Safety Examiner or Marine Surveyor will be able to advise those of you contemplating a new purchase whether or not he/she feels there is anything that could be improved for the future.

If you are having a new narrow boat built, you shouldn’t have any concerns. Just ask your canal boat builder to try and make things accessible for when something breaks in the future! Accessibility is crucial to remember if you are purchasing a sailaway narrowboat that you are fitting out yourself. Consider reproducing an electrical schematic to help you in the future, or for anyone that purchases your boat in the future.

Always ensure your or others work conforms to the Boat Safety Scheme and Recreational Craft Directive.

Electrics… Keeping A Record

When designing your narrowboat electrical circuit it is good practise to keep a set of diagrams of the cable runs, relating everything to the gauge of the wiring, fuse capacities, function etc.

In the future, it will be a lot easier to trace faults and add to the system. In fact it’s probably the only way to safely work out and plan the current carrying capacity of the individual circuits.

Make separated records and flow charts for DC and AC systems to avoid confusion. Keep these with your narrow boat records for easy access.

Understanding Electrics
