What is the difference between an electric, mixer and power shower?

The three names describe where the heat and the pressure come from, not the shape of the thing on the wall. Getting that straight is what decides which one you can actually fit.

Step by step

1. Identify your hot water system first.A combi boiler with no tanks, a hot cylinder in a cupboard with a cold tank in the loft, or an unvented cylinder with no loft tank. Every shower decision follows from this.
2. Understand the electric shower.It takes cold mains only and heats it as it passes over an element. It works on any system, gives hot water even when the boiler is off, but is limited to roughly 8 to 10 litres a minute at best.
3. Understand the mixer shower.It blends existing hot and cold. It gives whatever flow and temperature the house already provides, so it is excellent on a good combi or unvented cylinder and disappointing on weak gravity.
4. Understand the power shower.A mixer with a twin-impeller pump built in. It only works where both hot and cold arrive at low gravity pressure from a tank. It is not permitted on mains-pressure supplies.
5. Rule out the combinations that cannot work.You cannot pump a combi or an unvented cylinder. You cannot fit a power shower with no cold storage tank. An electric shower on a hot supply will destroy itself.
6. Weigh running cost honestly.An electric shower heats only what you use, which suits infrequent use. A mixer from a gas-heated cylinder or combi is usually cheaper per shower where the boiler is running anyway.
7. Consider what happens when the boiler fails.An electric shower is the only one that still works. In a household with one bathroom, that is a real argument for keeping one.
8. Check the flow rate before choosing.Time how long a bucket of known volume takes to fill from the bath tap. Below about 8 litres a minute, a mixer shower will disappoint regardless of the model.

Tips

• Ask 'where does the pressure come from?' before 'which model?'. It eliminates most of the catalogue immediately.
• A digital shower is a mixer with electronic controls, not a fourth category — the same system rules apply.
• Fitting or replacing an electric shower is notifiable electrical work; budget for an electrician.

Common mistakes

• Fitting a pump to a combi boiler supply — Combis and unvented cylinders are already at mains pressure. Pumping them is not permitted, can damage the boiler, and risks drawing water back into the mains.
• Choosing a shower before checking the flow rate — A high-end mixer on a weak gravity system performs worse than a cheap electric shower. The system, not the valve, sets the ceiling.

Alternatives

• Digital or smart mixer: A mixer with an electronic control panel and a remote processor box. Convenient and precise, but it is still a mixer and still limited by the system feeding it.
• Shower pump on a gravity system: A separate pump fitted near the cylinder that boosts a normal mixer. Effectively converts a weak gravity mixer into a power shower without replacing the valve.
• Whole-house pump or accumulator: Boosts everything rather than just the shower. More expensive, but it fixes weak taps and slow filling at the same time.

Questions people ask