An electric shower is among the most powerful appliances in the home, heating cold mains water instantly with an element of eight, nine or even ten kilowatts. That huge draw, used daily and often by several people, makes it worth understanding, though its short run keeps the per-shower cost lower than the frightening wattage suggests.
High power, short burst
The number on an electric shower is its power, not its cost. Ten kilowatts is enormous, far more than an oven, but a shower lasts minutes rather than hours, so the energy per shower is the power multiplied by that short time. A brisk shower costs a manageable amount; a long, daily one for each member of a household adds up to a real line on the electricity bill. The cost calculator, fed your shower's kilowatts and a typical duration, shows the figure for your own routine.
How it compares
An electric shower heats only the water you use, on demand, which is efficient in that nothing is heated and then left to go cold. But it heats with expensive electricity rather than cheaper gas, so a similar shower from a gas-heated mixer can cost less per minute even though both use hot water. Against a bath, a reasonable electric shower still uses far less, so the old advice to shower rather than bathe holds, provided the shower stays short.
Keeping the cost down
The lever is time, since the power is fixed. Shorter showers cost proportionally less, so a timer, or simply not lingering, is the main saving. Many electric showers have a lower power or eco setting for summer, when the incoming water is warmer and less heating is needed, so use it. Lowering the temperature setting a touch reduces the draw as well.
Showerhead caution
Unlike a mixer shower, an electric shower is not a good candidate for a low-flow head, since it controls its own flow and restricting it can cause problems. The saving here comes almost entirely from spending less time under it. Keep showers brisk and use the eco setting when you can, and a high-wattage shower need not mean a frightening bill.