outdoor
Hot tub and spa electrical supply
A dedicated hot tub supply costs £350 to £800 where the run is short. Book it before the tub arrives, not after: a tub delivered on a Friday with nowhere to plug in sits covered on the patio until somebody can dig a trench.
What this covers
What it costs. A dedicated supply is £350 to £800 on a short run. Full cost breakdown.
What the job covers
- Running a dedicated RCD protected supply to a tub
- Fitting an external rotary isolator within reach
- Sizing cable for a 13 amp or a 32 amp tub
- Burying armoured cable across a garden
- Certifying the circuit before the tub is filled
What is involved
Two ratings cover almost all domestic tubs and they are different jobs. A 13 amp plug-in tub runs from a suitable outdoor socket on an RCD protected circuit and heats slowly, because it cannot run the heater and the pumps together. A hard wired tub, usually 32 amp, gets its own circuit from the consumer unit in armoured cable, and that is what a tub that heats while the jets run needs. The supplier's manual states which, and it is the first thing an electrician will ask for.
A rotary isolator goes on a post or a wall within sight of the tub and at a distance from it set by the zones around water, so that somebody can kill the supply without reaching over the water to do it. Everything outdoors is RCD protected, the armoured cable is buried at depth with warning tape, and the whole circuit is tested and certified before the tub is filled rather than after, because testing a circuit with a full tub sitting on it is nobody's idea of a good afternoon.
The load is the conversation worth having early. A 32 amp tub on a house with a 60 or 80 amp main fuse, an electric shower and an EV charger is an arithmetic problem, not a preference. Sometimes the answer is load management, sometimes it is a supply upgrade through the network operator with its own timescale, and occasionally it is a smaller tub. All three are better discovered before the tub is ordered.
Choosing someone for the job
Get the manual to the electrician before you order, because the rating decides the whole job. Ask what the main fuse is and whether the total load works. Ask where the isolator goes and check you can reach it without leaning over the tub. Ask whether the trench and reinstatement are in the price.
Common questions
Can I just plug it into an outside socket?
Only a 13 amp tub, and only on a suitable RCD protected outdoor circuit. It will heat slowly because it cannot run the heater and the jets together. Anything larger is hard wired.
How close can the isolator be?
Outside the zones around the water, within sight of the tub, and reachable without leaning over it. That is the whole point of it: somebody should be able to cut the supply without approaching the thing that needs cutting off.