In technical terms the difference between 12Volt and 240Volt units is the incoming voltage to the unit. However, this is irrelevant to most, so how does this difference affect the choice of a heated towel rail.
Placement in the bathroom
Due to the low voltage, a 12Volt heated towel rail can be placed anywhere in the bathroom including in the shower area (i.e. opposite wall of an open ended shower) providing the transformer and any timers/switches are placed in the correct location according to the IP rating. However, a 240Volt heated towel rail can only go in certain zones of the bathroom which is determined by the IP rating of the towel rail. The majority of the Thermorail range of 240Volt heated towel rails have an IP55 protection rating which means that the rail will need to be located at least 600mm from a water source/spout. Be sure to always double check with you electrician that the heated towel rail you have selected is suitable for the position in the bathroom you have selected.
Wiring of the heated towel rail
12Volt heated towel rails can only be hardwired whereas most of the 240Volt range of towel rails have the option of being either hardwired or plugged into a power point. With a 12Volt rail the electrician will need to wire this into a transformer (supplied with all Thermorail 12Volt models) whereas a 240Volt rail is just wired directly to a 240Volt mains power supply. With the transformer for the 12Volt rails, this will need to be located outside of Zone 2 of the bathroom and within 2m of the rail with adequate access and ventilation.
Many people mistake low voltage (12Volt) with low wattage and therefore think that a 12Volt heated towel rail will not get as warm as a 240Volt towel rail however this is not the case. The wattage of the heated towel rail is what determines that heat output so a 12Volt and a 240Volt towel rail of the same size and wattages will put out an equal amount of heat.
Contrary to what many people think the voltage of the towel rail does not affect the running cost of the heated towel rail. The running costs are determined by the current draw or wattage of the heated towel rail so a 240V rail and a 12volt rail of the same wattage will consume the same amount of power and therefore costing the same amount to run. This being said all dry element towel rails are very economical to run and a rail of 600×800 size in either voltage will cost approximately 2cents per hour to run.
In conclusion, it is recommended wherever possible to use a 240Volt model fitted outside of Zone 1 in the bathroom and in cases where you need the towel rail to be in Zone 1 then choose a 12Volt model.