They can come in various shapes and
They can come in various shapes and sizes, but in all electric boilers, you’ll see water running through the system to be heated by a heating element – similar to the way a kettle works. Evidently the price stacks up quickly and that's before additions which aren't necessary but might be worth having, like thermostatic radiator valves (about £20 a radiator) or a wireless thermostat and controls (around £150). Gas pressure.