Recreational vehicle (RV) water heaters come in a wide variety of different configurations. The two main types of RV water heaters can be differentiated based on whether a tank is present. Traditional RV water heaters have small tanks that can hold three to ten gallons (about 11 to 37 liters) of water, though smaller and larger units are also available. These water heaters can be powered by liquid petroleum gas (LPG) or electricity, and may have pilot lights or remote starters. Tankless RV water heaters can also use either electricity or propane.
Many RV water heaters use tanks to heat and store a volume of water that is sufficient for washing dishes, showering, and other uses. The size of the tank typically corresponds to the capacity of the vehicle and how many people are likely to require hot water. Units with larger tanks are typically more expensive and can also take more propane or electricity to heat up.
RV water heater tanks are commonly made from either aluminum or steel and can be encased in expanded polystyrene, porcelain, or other insulating materials. Heater tanks that are made of steel typically include a sacrificial anode to prevent corrosion. This anode needs to be replaced somewhat regularly to avoid damage to the tank unit itself. Some manufacturers also offer secondary heating elements that can be inserted where the anode would normally be. These elements can perform the function of the anode while also heating the water more quickly.
The other main difference between RV water heaters that use tanks is the type of ignition. Many units use a pilot light that has to be lit, often from outside the vehicle, before the heater can start working. Other units use a remote ignition option so that the heater can be started up by just depressing a switch inside.
It is also possible to obtain RV water heaters in a tankless configuration. These tankless RV water heaters function in much the same way as home units, in that they use a heat exchanger to warm up water only when it is needed. This can save electricity or propane because there is no large tank of water to keep heated for long periods of time. Some new RVs come with these units already installed, though it is sometimes possible to retrofit an old motorhome or travel trailer with a tankless unit that simply slides into the same space that the old heater occupied.