There are two versions: traditional ones that are plumbed like a radiator with water heated from a central boiler, and electric ones where an electrical resistance heats water or oil contained in the unit.
The finish can be in chrome plating, polished steel, or lacquer.
In these cases, the dryer is heated by hot water in wintertime, and by electricity in the summer.
A towel dryer, with high output, can also serve as a radiator in a small bathroom.
There are towel warmers of different sizes, from (50 by 70 centimetres (20 in × 28 in)) to those two metres (6 ft 7 in) in height.