How to Fit an Electric Shower: Regulations, Costs and What You Can DIY
Electric showers are the most common shower type in the UK, fitting roughly 60% of new shower installations. They take cold water directly from the mains supply and heat it on demand — no boiler, no stored hot water, no waiting. Installing one involves both plumbing and electrical work, each with specific regulatory requirements that affect what a DIYer can legally do.
The Regulatory Framework
Plumbing: Connecting to the cold mains supply is notifiable plumbing work under the Water Supply (Water Fittings) Regulations 1999. A DIYer should notify their water company — the notification is free and ensures compliance. In practice, this work is straightforward and frequently done by homeowners.
Electrical: An electric shower requires a dedicated circuit from the consumer unit — it cannot share a circuit with any other appliance. Installing a new circuit from the consumer unit is classified as consumer unit work under Part P of Building Regulations, which must be carried out by a registered electrician. This is not negotiable. A competent DIYer can install the shower unit itself (mount it, connect the plumbing, and connect the wiring at the shower end), but the circuit from the consumer unit requires a Part P-registered electrician.
Choosing the Right Electric Shower
Electric showers are rated by power: 7.5kW, 8.5kW, 9.5kW, 10.5kW. Higher wattage provides a better flow rate in cold weather when the incoming water is cold. For most UK homes with normal mains pressure (at least 1 bar dynamic pressure), a 9.5kW or 10.5kW unit gives a comfortable shower experience.
Check your mains water pressure before specifying — low-pressure properties (common in hilly areas or at the top of tall buildings) may need a pressure-boosting pump in addition to the shower unit. Brands: Triton, Mira, Aqualisa — all produce good quality units at £100–300 for the shower unit alone.
What Cable Size Does an Electric Shower Need?
This is specified by the shower's current draw and run length:
- 7.5kW shower: 32A circuit, 6mm² cable, 32A MCB
- 8.5–10.5kW shower: 40A circuit, 10mm² cable, 40A MCB
The cable runs from the consumer unit to a ceiling-mounted double-pole isolator switch outside the bathroom, then to the shower unit. The isolator must be outside the reach of a person standing in the shower (zone 2 or beyond).
The Plumbing Connection
Electric showers connect to the cold mains supply via a 15mm branch pipe. The connection point is usually the nearest 15mm cold water pipe — often under the bathroom basin or from a pipe running to the toilet cistern. Install an inline isolation valve on the branch to allow the shower to be isolated without turning off the entire water supply.
Run 15mm copper or flexible plastic pipe from the isolation valve to the shower unit's water inlet (typically at the back of the unit, or at the base). The shower unit contains its own flow regulator — no additional pressure regulation is usually needed at the connection point.
Installing the Shower Unit
- Mark and drill fixings into the tile/wall surface — use a tile drill bit for glazed tiles to prevent cracking.
- Feed the water pipe and electrical cable through the designated entry points in the shower unit (usually at the back or base — check the manufacturer's diagram).
- Mount the shower unit to the wall.
- Connect the water supply at the inlet valve — use PTFE tape on the thread and hand-tighten plus a quarter turn with a spanner.
- Connect the electrical cable at the terminals inside the unit — follow the manufacturer's wiring diagram exactly. This is the section the electrician will make at the consumer unit end and the isolator, but the connection inside the unit itself can be made by a competent person.
Testing and Commissioning
Before switching on, turn on the water supply and check for any leaks at the connection. Open the shower control to flush any debris from the supply pipe before the unit is powered. The electrician who commissioned the circuit should carry out an insulation resistance test and continuity test before issuing the Part P certificate.
Costs
- Shower unit (9.5kW): £120–250
- Shower tray, enclosure (if new installation): £150–500
- Electrician for dedicated circuit: £300–500
- Plumbing materials: £30–60
- Total installed cost (no enclosure): £500–800 DIY+electrician; £800–1,400 fully professional
