Boat Heating Installation: the Electrical Side
A diesel heater turns a cold boat into somewhere you want to be in spring and autumn, but it is also one of the hungriest electrical loads aboard when it starts. For boat heating, we look after the electrics of Webasto and Eberspacher installations: the supply, fusing, controller and the battery capacity behind it.
Heater faults that look like fuel or combustion problems are often electrical. A glow plug draws heavy current on start-up, and a supply that sags under that load can cause failed starts, error codes and shutdowns.
We are based at Shoreham Airport and work aboard at the berth between Brighton and Southampton.
What the electrical installation covers
The heater needs a dedicated, correctly sized supply from the battery with protection close to the source, so start-up current does not starve other circuits. The controller or thermostat is positioned where you can reach it and where it reads a sensible cabin temperature. Fuel lines, exhaust and through-hull work need the heater maker's procedures and are agreed separately in the scope.
- Dedicated supply cable sized for start-up current
- Fuse or breaker close to the battery
- Controller, timer or thermostat wiring
- Checks on battery capacity and charging
Battery capacity and heating
Running a heater overnight takes a steady draw from the batteries, and the start and stop cycles add more. On a tired lead-acid bank that can mean waking up to a cold boat and a heater that refuses to restart. We look at your bank and charging before adding heating, and where a lithium upgrade makes sense we will explain why.
Lithium battery upgrades · Battery monitor installation
What is the best boat heating system?
For most boats without a generator, diesel-fired warm air heating is the usual choice because it uses fuel already aboard and modest battery power. Electric heating only makes sense when you are on shore power, where it must be sized to the shore supply. Hot water systems suit larger boats. We advise on the electrical implications of each so the choice fits the boat.
Before work starts
Tell us the boat, the heater and where the batteries are. We check the supply route and give you a written quote. If you have an existing heater that is misbehaving, we can test the electrical side first.
Heater controllers and timers
Modern heater controllers let you set a timer so the cabin is warm when you arrive, and some can be operated from a phone. Their wiring is low current but sensitive to poor connections, and an intermittent controller cable is a common cause of error codes. We route it away from heavy cables, secure it properly and check the connection at the heater before handing over.
If the boat has an older heater that has been unreliable for a while, it is often worth testing the electrical supply under start-up load before deciding the unit itself needs replacing.
Frequently asked questions
Do you install Webasto and Eberspacher heaters?
We carry out the electrical side of these installations: supply, protection, controller and battery checks. Fuel and exhaust work is agreed separately.
Why does my boat diesel heater fail to start?
Low voltage during the glow plug start is a common cause. Undersized cable, poor connections or a weak battery can all be to blame.
Can I run electric heating on my boat?
Only sensibly on shore power, and sized to what the shore supply can deliver.
How much does boat heating installation cost?
It depends on the heater and the cable route. We assess first and quote in writing.
Want a warm boat this season?
Send the boat details, where it is kept and what you have in mind, and we will come back with the next step and a written quote.