How Electric Showers Work
An electric shower is the universal solution to a hot shower. It heats cold mains water inside the unit, so it doesn’t depend on your boiler, your hot-water tank, or whatever else is using hot water in the house at the same time. That makes it the simplest type to fit in any home with mains cold water and an electrical supply, and the one that keeps working when the boiler doesn’t.
Cold water enters the shower unit straight from your mains. Inside the unit, a heating element heats the water on demand as it flows past, the same principle as an electric kettle but with the water moving constantly. The temperature is controlled by how fast the water flows: slower flow gets hotter, faster flow gets cooler. That’s why an electric shower’s flow rate is always more modest than a powerful mixer — it can only heat the water as fast as the element can keep up.
There’s no boiler involvement at any stage. The shower needs cold mains water, a dedicated electrical connection, and that’s it. If your house has both, an electric shower works.
What kW means
The kW rating is the most important number on an electric shower. It tells you how much electrical power the heating element draws, and that decides how much hot-water flow you get. Rough rule of thumb:
- 7.5 to 8.5 kW: entry-level. Adequate hot flow in summer, weaker in winter when the incoming mains is colder. Best for an occasional-use bathroom or where mains pressure does the heavy lifting.
- 9.5 kW: the popular middle ground. Decent flow year-round in most UK homes and the most common pick.
- 10.5 to 11 kW: strong flow for a daily-use family shower and the better choice if your incoming mains gets properly cold in winter. Needs the wiring to match — higher kW needs heavier cable.
Higher kW means a stronger heated flow, not a hotter shower. The element can heat more water in the same time, so you don’t have to slow the flow as much to get a comfortable temperature. In a cold-winter or daily-family-use scenario, that gap matters.
When to choose electric
Three situations where an electric shower is usually the right answer:
- In a second bathroom or en-suite. The shower runs independently of the boiler, so two people can shower at the same time without one of them going cold. Often the smartest pick for an en-suite or a converted loft bathroom.
- On a gravity-fed water system with weak hot-water pressure. An electric shower doesn’t use your hot water at all, so it works around the pressure problem rather than needing a pump to fix it.
- As an immediate replacement. If you’re swapping an existing electric shower, it’s usually a like-for-like swap onto the existing pipework and electrical supply (subject to the new unit matching the supply spec). Fast install, minimal disruption.
Trusted brands
Mira and Triton dominate the UK electric shower market for good reason. Mira make ranges including the Sport, Advance and Decor — well-engineered units with strong cold-water performance, often the first pick for serviceability and longevity. Triton’s T80 and T90 ranges are the long-running mainstream alternative, with broad model choice across kW ratings. Aqualisa round out the top three, with strong digital and remote-control variants. We stock all three brands plus Bristan and Gainsborough, so most popular models are covered.
Supply and installation
Electric showers have two install requirements beyond the cold-mains feed. First, a dedicated electrical circuit from the consumer unit, sized for the unit’s kW rating: a 10.5 kW shower needs heavier cable than a 7.5 kW one, and the circuit needs an appropriate RCD-protected breaker. Second, a pull-cord isolator switch in the bathroom (or just outside it) so the shower can be switched off safely.
This isn’t a DIY job. Both the electrical work and the water connection need a qualified tradesperson — a Part P registered electrician for the wiring and a plumber for the supply, often working together. A like-for-like replacement is usually quicker because the existing supplies are already in place; a first install needs the wiring run from scratch. Either way, factor that into your shower budget.
Electric shower FAQs
Will an electric shower work with my water system?
Yes, as long as you have a cold mains supply. Electric showers heat the cold water themselves, so they don’t need hot water from your boiler or cylinder. That makes them compatible with combi, unvented mains, gravity-fed and any low-pressure system.
What kW electric shower do I need?
9.5 kW is the popular middle ground for everyday use. Choose 10.5 to 11 kW if you want a stronger flow or your mains runs properly cold in winter. Stick with 7.5 to 8.5 kW only for occasional-use bathrooms or where your wiring won’t support a higher unit.
Can I fit an electric shower myself?
No. The electrical work needs a Part P registered electrician and the water connection needs a plumber. The wiring is heavy (typically 10mm² cable) and the circuit needs its own breaker, so this isn’t a job to take on without the qualifications.
How long does an electric shower last?
Most units last seven to ten years. The heating element scales up and eventually fails, especially in hard-water areas. Many parts are replaceable, but at that age it’s often easier and not much more expensive to fit a new unit.
Why is the flow on my electric shower weak?
Electric showers always have a more modest flow than a powerful mixer because the element can only heat water as fast as the rating allows. In winter, the incoming mains is colder so the flow has to be slowed further to hit the same temperature. A higher kW unit gives you more flow headroom.
Filter the grid above by kW, brand and finish to find the electric shower that suits your bathroom, or read electric vs mixer vs thermostatic showers if you’re still weighing up the type.
We’ve been helping people fit out bathrooms since 1999, with a 4.8/5 rating from over 60,000 Trustpilot reviews, free UK delivery, a price match promise and 365-day returns, so you can buy with confidence.
Big brands, small prices.