Electric showers

Last updated: October 9, 2008.

Are you a shower person or a bath person? Do you like to feel pulsing jets of water blasting your dirty skin clean? Or do you prefer to laze luxuriously in the tub until the water turns cold? If you wash for less than five minutes and your shower has a modern, low-flow head, you'll save over 50 gallons of water and a huge amount of energy compared to taking a full bath. Saving hot water with a shower helps to cut your energy bills and it's a simple thing you can do to fight global warming. Sounds good? Let's take a closer look at how showers work!

Photo: A simple Mira electric shower. There are two controls for adjusting the temperature. The upper dial sets the temperature broadly as high, medium, or low. Once you've set the temperature roughly, the lower dial lets you fine tune to get the water exactly as hot as you want it.

How do mixer showers work?

The simplest showers are called mixer showers and, as their name suggests, they work by mixing hot and cold water from separate pipes to make warm water whose temperature is somewhere in between. The most basic form of mixer shower is a Y-shaped rubber pipe that you fit over the hot and water faucets on a bath-tub. By adjusting the faucets, you create a single stream of water at exactly the temperature you want.

The trouble with mixer showers like this is that the temperature is hard to control. If someone switches on a cold faucet or flushes a toilet elsewhere in your home, the cold water supply is suddenly reduced. That means there's proportionally more hot water coming through your shower and, if the water's too hot, you could be scalded. The opposite will happen if someone switches on a hot faucet—you'll suddenly find the shower turning freezing cold!

Mixer showers that are plumbed into the wall overcome this problem by using built-in thermostats and safety cut-outs. They constantly adjust the temperature of the mixed water to ensure you're not boiled like a lobster or frozen rigid by water that's alternately too hot or too cold. Most mixer showers also have safety cut-outs that prevent you from turning the water up to dangerously high levels, which is good news if they're being used by elderly people or young children.

But there's still a basic problem with mixer showers: they typically run off hot water from a tank. Once the tank is empty, there's no more hot water and you have to wait for the tank to fill up before you can shower again.

How does an electric shower work?

Electric showers overcome this problem by heating cold water with electricity. They never run out of hot water, so they're a great solution if you have lots of people in your house who like to shower one after another.

Electric showers work in much the same way as other electric appliances that get hot, including electric toasters and hair dryers. They send an electric current through a piece of metal called a heating element. This has a high resistance, so it gets really hot when electricity moves through it. Cold water flows past the element, picking up heat and heading out through the nozzle where you're standing.

You probably know that water and electricity are usually a very dangerous combination, but electric showers are perfectly safe if they're properly fitted. That's because a heating element is a completely sealed unit. The electric current flows through the element, but not in such a way that it can give you a shock. No electricity comes into contact with the water that touches you.

You can adjust the temperature of an electric shower by turning a dial, which is usually marked with a scale running from blue (for cold) to red (for hot). This controls a thermostat that cycles the heating element on (to make the water hotter) and off (to cool the water down) so it always remains at exactly the temperature you set.

How do power showers work?

For an electric shower to work effectively, you need a cold water supply with reasonably high water pressure to begin with, because the shower heating unit will reduce the pressure of the water as it flows through. If you don't have enough water pressure for an ordinary electric shower, the solution is to fit a power shower. It takes in and heats cold water just like an ordinary electric shower, but it also uses an electric pump to increase the water pressure so it leaves the nozzle with greater force and higher speed. If saving water and energy is important, bear in mind that power showers use 3-5 times more than ordinary showers. That means a lengthy power shower can easily cost you as much as a generous bath-tub full of hot water!

Do showers save energy compared to baths?

Photo: You can adjust the water flow rate on this Mira shower by turning the shower head. The water flows out through one of three different sets of nozzles to give a gentle spray, a medium shower, or a high-pressure water massage.

Which costs more, a shower or a bath? Generally, showers use less energy because they use less water, but it all depends on your shower and your bath. If you have a modern electric shower with a low-flow head and you use it for only three or four minutes, it'll be very efficient and should save you money compared to taking a bath. If you have a power shower and you stand under it for 15 minutes, don't expect to save much—you may even find it costs you more! If you have a shower over your bath-tub, the simple way to test whether you're saving anything is to take a shower with the plug in place. If you use less water, you're saving energy and money; the less hot water you use, the more you save. (Of course, the calculation changes somewhat if your shower is using hotter water than your bath.)

If you have a separate bath-tub and shower cubicle, comparing costs is more tricky. If you know your math, you could read your electricity (or gas) meters before and after taking a bath and shower and calculate the cost using the difference in the readings. Or you could use an electrical energy monitor, though that won't help you if either your bath or shower is powered by gas or oil!