Hot tubs and the 13 A plug: what it can and cannot do

Every tub on this site is sold as a portable tub you can run without an electrician. That only works because the makers design them around the limits of a normal UK plug. Once you know those limits, you understand why the bubbles sometimes switch the heater off, and why a 13 A tub heats slowly.

The sum behind the plug

A UK plug is fused at 13 A. Mains voltage in the UK is 230 V. Power is current times voltage:

13 A × 230 V = 2,990 W

So a single 13 A socket can deliver just under 3,000 W, or 3 kW, and that has to cover everything the tub runs at the same moment: heater, filter pump, bubble blower and, on some tubs, a jet pump.

What the makers publish

Six tubs in our data give a heater wattage. The rest do not, and Lay-Z-Spa, Wave and MSpa do not publish it for any model we list.

What a 13 A plug can do

• Run a 2,200 W heater with headroom. 2,990 W minus 2,200 W leaves about 790 W for the filter pump.
• Run an 1,800 W heater and a 600 W blower. On the Arebos that adds up to 1,800 + 600 = 2,400 W, inside the limit. The listing does not say whether the tub runs both at once, so check the manual.
• Heat a tub from cold. Slowly. See how long a hot tub takes to heat.

What a 13 A plug cannot do

• Run everything on the Intex Jet & Bubble Deluxe at once. 2,200 + 800 + 1,000 = 4,000 W. That is about 1,000 W over the limit, so the tub has to switch some motors off while others run.
• Heat while you blast the bubbles or jets, on most tubs. The control box stops the heater while the blower runs so the socket is not overloaded. Long sessions with the bubbles on let the water cool.
• Match a hard-shell tub. Acrylic hard tubs use 32 A wired supplies and heaters of several kilowatts. See inflatable, foam or frame.

Plug and play: what it means

"Plug and play" means the maker confirms the tub runs straight from a 13 A socket. In our data it is confirmed for eight tubs:

• MSpa Oslo, Tuscany, Tribeca, Denver and Aero Plus
• Canadian Spa Co. Grand Rapids
• Aoxun 208 cm and Nordivale Square 4-6, which both come with an RCD plug for a 13 A socket

For the other 24 tubs the listing does not confirm it either way. That does not mean they need hard wiring. It means you should read the manual before you order.

Plugging in safely

• Use an outdoor socket with RCD protection. An RCD cuts the power in a fraction of a second if current leaks to earth, for example through water. Many tubs have an RCD built into the plug or lead; a protected socket gives you a second layer.
• Do not use an extension lead. A tub draws close to 13 A for hours. Extension leads, and coiled leads in particular, heat up under that load.
• Do not use a multi-way adaptor.
• Keep the plug off the ground and away from splashes.
• Have an electrician fit an outdoor socket if you do not have one near the tub. It is a small job compared with the cost of the tub.

What this means for your electricity bill

A heater on full power uses its wattage every hour it runs. At 25p per kWh:

Your tariff differs, so swap in your own unit price. A smaller heater is not cheaper to run for the same rise in temperature: it uses less power each hour but runs for more hours. More on this in what a hot tub costs to run.

Quick answers

Can I run two hot tubs from one double socket? No. Both outlets share one circuit and one supply cable.

Does a bigger heater need a bigger plug? Above about 3,000 W, yes. That is why the portable tubs here stay at 2,200 W or less where the maker publishes a figure.

Can I put the tub on a timer plug? Ordinary plug-in timers are not rated for this load for hours on end. Use the tub's own timer or app. See our wifi hot tubs guide.

Before you choose a spot, read where to put a hot tub.