I’ve been asked a few times why water efficient shower heads, or flow regulation devices, aren’t suitable for electric showers. There are two main reasons.
Firstly, electric showers have to heat water from the cold supply up to a comfortable shower temperature (about 40 degrees centigrade), which takes a lot of energy. Even at a rating of 7.5-10 kilowatts this means that electric showers can only handle a relatively low flow of water through them, from 3-9 litres per minute, with an average flow of 6 litres per minute, according to a survey by Waterwise. Since most water efficient shower heads and flow regulators are set to a flow rate of 7.5-8 litres per minute there are no savings to be made by fitting these to an electric shower.
Secondly, there have been concerns about possible damage to showers due to any flow restriction devices.
So, electric showers already fall into the “water efficient” range, which is great for residents to know. However, at 7.5-10 kilowatts electric showers use electricity faster than any other electrical item in the home. One unit of electricity (one kilowatt hour) will power a 40 watt lightbulb for 24 hours. It would only power a 10 kW electric shower for 6 minutes. So, even with an electric shower, saving water through shorter showers will also save money.