appliances
Electric shower installation
Swapping an electric shower for one of the same rating costs £200 to £450. Going up in rating is a different job, because a 10.5kW unit draws more than twice what a 4.8kW immersion heater does, and the cable and the protective device behind the wall were sized for whatever was there before.
What this covers
What it costs. A like for like replacement is £200 to £450 including a mid range unit. Full cost breakdown.
What the job covers
- Replacing an electric shower like for like
- Upgrading cable and protection for a higher kilowatt unit
- Fitting a pull cord isolator to the correct rating
- First fitting a shower where no supply exists
- Checking bonding and RCD protection in the bathroom
What is involved
A like for like swap is short. The circuit is isolated, the old unit comes off, the new one goes on the same cable and the same water feed, and the installation is tested. Most of the fiddle is plumbing rather than electrical: getting the inlet to line up so the tiles do not have to come off. What turns the job is a change of rating, because cable size, the protective device and sometimes the pull cord isolator all follow the kilowatt figure, and a 10.5kW shower on a cable sized for 8.5kW is a fire risk rather than a compromise.
A shower is a bathroom circuit, which brings its own rules. Residual current protection is required. The pull cord isolator has to be out of reach of somebody in the bath or the shower, which is why it is on the ceiling. Any supplementary bonding between pipework and the earth depends on whether the rest of the installation already satisfies the conditions for leaving it out, which is one of the things an electrician checks rather than assumes.
Performance disappoints for reasons that have nothing to do with the shower. An electric shower heats water as it passes, so its output in litres a minute falls as the incoming water gets colder, and the same unit that was fine in August feels weak in February. Rating decides how much heat it can add, and nothing else does. If the incoming cold main is poor, a more powerful shower will be hotter and no faster, and that is the fact worth knowing before spending money on the upgrade.
Choosing someone for the job
Ask what rating the existing cable and protective device will support before choosing a unit, not after. Ask whether the price includes a new pull cord isolator. Ask whether making good is included if the cable has to be upgraded and the wall opened. Get the existing shower's kilowatt figure off its front panel before phoning anybody.
Common questions
Can I fit a more powerful shower?
Only if the cable and the protective device support it. Going from 8.5kW to 10.5kW often means a larger cable back to the consumer unit, which is the difference between a two hour job and a half day with a chase in the wall.
Why is my shower weaker in winter?
Because it heats water on the way through. Colder incoming water means less flow at the same temperature. It is the normal behaviour of every electric shower and a bigger unit is the only thing that changes it.