If you are looking to install a shower in your bathroom then among the options open to you will be an electric shower. Choosing a mixer shower or power shower will depend on your heating system but electric showers run independently of your central heating so can be used in any household - providing it has water and electricity.
Electric showers work by instantly heating water. Cold, mains pressure water is fed into the unit an passes over a heating element inside a chamber. The power rating of this element will determine the amount of water that can be heated. As well as a model name, many electric shower manufacturers will include the power rating of the shower in the description, which will be given in kilowatts. Showers with a higher kilowatt rating will be able to heat more water in a given time, so a higher figure gives a better flow rate. Very early models had ratings less than 6kw so the spray that they produced was very fine with a low water flow rate, but over the years kilowatt ratings have steadily increased with some current models rated over 10kw.