Starting at £2,500 to buy and install, a boat heater will keep the interior of your boat hale and hearty, allowing you to extend the sailing season and take advantage of fine winter weather. It is also a must for anyone eyeing northern cruising grounds.
The humble boat heater has come on considerably when the old coal-fired bulkhead stoves of the last century. The top selling brands are based on a remote diesel burner that heats fresh air via a heat exchanger and uses a powerful fan to circulate that hot air around the boat through insulated ducting.
This system has the advantage of running off the same tank as your main engine, using a fuel which is generally not considered dangerous to handle because it does not ignite easily. The combustion unit can also be positioned somewhere conveniently out of the way – it doesn’t have to be below.
There is another option in the form of propane/butane heaters. They also blow hot air around the boat, but run from the boat’s cooking gas supply. Some can also be usefully hooked up to 230V power to run off the shore supply when you’re in a marina.
Finally, there is a range of more traditional stove-type heaters for mounting against the boat’s bulkhead. These run on diesel, paraffin and even kerosene, but the combustion takes place in the space to be heated, with dangerous gases vented via a chimney.
Eberspächer Airtronic Air Heater
Recommended for boats from 13ft up to 62ft, the Airtronic is available in four sizes, with the 2.2kW Airtronic D2 suitable for boats 13-32ft, the 4kW Airtronic D4 Plus for 26-99ft, the 5kW D5 for 39-49ft and the 8kW D8LC for 49-62ft.
The Airtronic blows warmed air into each cabin of the boat through a flexible duct system and is controlled by a thermostat in the saloon plus, in each cabin, vents (now available in white) that can be opened or closed to let more or less hot air through.
A smaller heater will burn about one gallon of diesel every 20 hours. All sizes need a 12V or 24V electricity supply. The number of cabins and heads on the boat dictates the number of outlets. Exhaust is usually via the transom, above the waterline, meaning the heater can be run while the boat is heeling.
Prices start at £1,826, rising to £5,500. Installation by Eberspächer is from £522 to £1,225.
Webasto Air Top
The German manufacturer makes three blown-air models that range from 2kW to 5.5kW in heat output.
The unit initially draws around 20A to heat a glow plug, which ignites the diesel (there is no compression, as in a car engine), but once it is warmed up consumption drops dramatically. It is, in fact, the fan that pushes the heated air around the ducting that consumes the most power. For the 2kW unit, this amounts to a total draw of between 1A and 2.5A at 12V, depending on how hard the unit is running. For the larger units (which work on both 12V and 24V), current draw can run up to 95W.
Webasto says its products don’t need annual servicing. The burner unit may need occasional cleaning, but frequency is determined more by the cleanness of the fuel used than by how regularly the heater is turned on.
Controls are simple to use, with the option of standard heating, fast heating, eco mode (low power consumption) and ventilation only. The more complicated control unit allows programmes to be set and enables a remote control that works up to 1,000m from the boat.
Price from £1,508 for the 2kW unit.
This manufacturer builds diesel and paraffin heaters of the blown-air variety, ranging from 2kW of output to 4kW, said to be enough to heat a 50ft boat. Being Finnish, Wallas should be up to dealing with cold northern conditions.
It makes great play of the units’ quietness and relative low power consumption. Thanks to what Wallas calls a ‘laminar’ burn, the mix of fuel and air is very precisely controlled for cleaner combustion and no noise.
It requires the same high start-up current as the Webasto and the Eberspächer, but the ongoing power demand is lower than the others because the fan uses less electricity.
It has an elegant controller that can either be flush- or bezel-mounted. The default mode uses thermostatic control, with a fast heat-up followed by a steady blow that keeps the temperature level. There is a manual override, a dryer mode with faster fan speed and a ventilation-only mode.
You can buy a remote-control gadget (£375.82) that plugs into the control unit and allows you to operate it from your smartphone via the mobile network.
There are also kerosene/paraffin versions available, but these are aimed at the inland market, where the main engine doesn’t use diesel.
Price from £1,720 for the 22DT kit.
UK distributor: kurandamarine.co.uk
As the name suggests, these heaters run on LPG – propane or butane. They are larger than the diesel-powered units and cheaper, but otherwise share many of the same characteristics and rely on circulating hot air around the boat.
Propex heaters come in two models – one rated at 2kW and the other 2.8kW. There is a ‘dual fuel’ option for the smaller heater, which allows it to be run off mains electricity as well as gas. At 230V, the heater draws a reasonable 9A of power to reach its full 2kW output.
The drawback to this unit is that it gets through gas far more quickly than you’d consume diesel. The standard 907 Campingaz bottle found on many boats would give just 19 hours’ burn time on the small heater and only 12 hours on the 2.8kW model. This might be acceptable for occasional use or where your boat has a larger gas bottle.
An important difference from diesel heaters is that the only exhaust is carbon dioxide and water vapour, which Propex claims makes it odour-free and more environmentally friendly. And because gas ignites easily, there is no need for glow plugs with a high start-up current. The only power needed is for the fan, which draws a fixed 1.4A in the small heater or 1.9A in the bigger one.
As with the Webasto, the microprocessor keeps the fan speed stable no matter what the battery voltage, and with the balanced fan and ball-race bearings, this is a quiet operator.
Price from £570.
Dometic Origo 5100
The very simplest type of heater resembles a Cobb barbecue. It runs on refillable 750ml cartridges of pure alcohol, and can generate 1.5-2.0kW.
“Enough to extend the season by a couple of weekends,” says Stuart Jones of Dometic.
Free-standing and unventilated, it will produce heat but also water vapour and carbon dioxide. It is sold in many chandleries.
This is understandably the cheapest of the options at £176.
This range of small, compact diesel heaters comes from the same stable as the Canadian Dickinson, right. Simpler and cheaper, they do much the same job with models from 3kW (the Sig 100 – pictured, above) to 4.7kW maximum output.
Prices start at £728.40 for the Sig 100, with extra for flue assembly according to the complexity of the installation.
UK distributor: kurandamarine.co.uk
Canadian heater maker Dickinson offers four diesel stove models, all rated up to 4.7kW. Like the Refleks, they need careful mounting on either floor or bulkhead, with a flue and air intake assembly. An optional flue fan draws 0.17A. The model pictured (Antarctic – £938) has a large flat top with a fiddle for cooking and heating, and all are compatible with separate water heaters. Dickinson also makes a solid fuel heater for smaller boats.
Prices start at £818.40 for the stove – flue assembly extra.
UK distributor: kuranda marine.co.uk
A staple in the classic yacht world, Refleks is the Danish specialist in free-standing diesel heaters, which radiate heat directly in the cabin. Their units range in power from 1.6kW to 5.8kW and will take the chill off very quickly. They need careful positioning to keep them adequately ventilated, plus a fresh air intake and a chimney to vent exhaust, making installation more complicated. Will not run for long periods heeled.
Prices start at c£970.