A Guide to Hot Tub Electrics: Supply, Costs and Who Does What (UK and US)

Last updated: September 2026

If you plan to heat your hot tub with an electric heater, you need electricity. Sounds obvious, right? But in most cases it isn’t as simple as plugging into an outlet. You’ll need a dedicated supply, and the decisions you make early on (where the control room goes, where the cable runs, how much current you need) affect everything else.

Most of this is a job for a qualified electrician. Getting it wrong is dangerous and may even void your insurance. But you need to understand what you’re asking for, so you can plan the build and talk to your electrician on the same page. That’s what this guide is for.

Who does what

On a DIY build, you do a lot yourself, but the supply isn’t one of those things.

Job	Who
Choosing the spa pack, pumps, heater and heat pump, and adding up the load	You (then confirm with your electrician)
Planning the control room and cable route, and laying ducts before concrete	You
Mounting the pack and plugging in pumps and blower (power isolated)	You
Circuit design, cable sizing, RCD or GFCI, isolator or disconnect	Electrician
Final connection at the pack’s terminal block, testing and certificate	Electrician
Part P notification (UK), or permit and inspection (USA)	Electrician (UK), you or your electrician (USA)

The step-by-step of what’s connected where is in Hot tub wiring explained. This guide is about planning the supply.

The building blocks of a hot tub supply

A dedicated circuit

You need your own dedicated circuit for the tub. That means a breaker (and in the UK, ideally an RCBO) in your consumer unit or panel that feeds only the hot tub. If the hot tub trips, the rest of the house stays on, which is exactly how it should work.

Shock protection: RCD or GFCI

This is the bit that keeps you alive. In the UK, it’s a 30mA RCD, and Total Skills is clear that it must be at least Type A, because a basic Type AC RCD isn’t sufficient for a hot tub’s electronics. In the USA, NEC Article 680 requires GFCI protection, usually from a GFCI breaker in a spa disconnect panel. The wiring guide goes into both.

A local isolator or disconnect

During planning, think about where the isolator goes. It lets you (or anyone else) kill the power to the tub quickly in an emergency, and it’s what you switch off before working on the equipment.

• UK: a weatherproof (IP65 is typical) rotary isolator rated for the circuit, within sight of the tub but at least 2m (6ft 6in) from the water, so nobody can reach it from the tub. The IET gives the same 2m, and recommends fixed wiring rather than a socket.
• USA: a maintenance disconnect within sight of the tub, at least 5ft (1.5m) horizontally from the inside wall (NEC 680.13). Usually this is the GFCI spa panel.

Your electrician will use weatherproof glands on every entry, and a proper connection at the pack. Where the control room sits drives all of this, so read Hot tub control room position first.

Outdoor cable

Outside, the cable needs protecting from spades, mowers and anything else. In the UK that’s normally steel wire armoured (SWA) cable. In the USA, it’s usually copper conductors in conduit.

In my case, I fixed the armoured cable along the length of my garden wall. The alternative was to bury it, which means a lot of digging. I chose the wall-mounted route, in armoured cable, because I didn’t want to worry about my kids running their bikes and toy cars into it. It’s more expensive, for sure, but it’s worth it for peace of mind.

If you do bury it in the UK, Total Skills gives a minimum of 500mm (20in) in a garden, or 600mm (24in) where vehicles can drive over it, with warning tape above. In the USA, the depth depends on the wiring method, so ask your electrician or inspector. The wiring guide has the detail.

Voltage and frequency: UK vs USA

You must supply the right voltage and frequency for your heater and pumps. They’re designed for one or the other.

	UK and Europe	USA
Supply	230V single phase (often called 240V), 50Hz	120/240V split phase, 60Hz
What the hot tub uses	230V: line, neutral and earth	240V: two hot legs (L1, L2), neutral and ground
Typical DIY circuit	16A, 32A or 40A	Typically 50A (depends on the pack)
Protection	30mA Type A RCD, Part P	GFCI, NEC 680, permit

You can’t take a heater from the UK, connect it to a US supply and expect it to work, or the other way round. Don’t worry, though. All the pumps and heaters I supply are designed for the country they’ll be used in.

Frequency matters for pumps too, because it sets how fast the motor spins. A 60Hz supply runs a motor 20% faster than 50Hz. So a 50Hz pump on a 60Hz supply would spin 20% faster than it was designed to, which overloads the motor and makes it overheat. (Put the other way round, a 50Hz motor spins about 17% slower than a 60Hz one.)

USA: do I really need 240V?

Yes. To run a DIY hot tub in the USA, you need 240V at 60Hz.

You’ll see pumps and heaters online rated at 110–120V, 60Hz. Honestly, trying to take a shortcut here won’t work. Spa packs and pumps that run on 120V just aren’t powerful enough. A standard 15A circuit at 120V gives you about 1.8kW in total, for everything. Shop-bought “plug and play” tubs manage by not running the heater and pumps at the same time, as Bullfrog Spas explains. A block or concrete tub holds far too much water for that. At 240V, the ACC pack I use runs a 5.5kW heater.

You’ll still hear the US standard called “110V”, but it’s usually quoted as 120V, and the split supply as 120/240V.

Don’t worry, you almost certainly have 240V already

Most American homes have a split-phase supply: two 120V legs coming in. Measured between the two legs, you get 240V. That’s how your dryer and range get their power.

Image credit: www.signatureinspectionshawaii.com

For your hot tub, the electrician takes a feed from L1 and L2 (240V) plus a neutral and ground, which is the 4-wire supply most spa packs need. The circled outlet in the diagram above shows the idea. So the chances are you already have the 240V supply you need, and your electrician just has to wire it up correctly for your hot tub.

Why 240V?

It comes down to current versus power. Power is voltage times current. To get the same power at 120V, you need double the current, which means much thicker cable and bigger breakers. Across a whole system of pumps, blower and heater, that becomes impractical, which is why hot tub equipment is designed to run at 230–240V.

How to work out the current you need

I used to add up the current of each component (pump, blower and the spa pack on full heat), which came to 57A, and recommend a 60–65A supply. That double counts. The pumps and blower plug into the spa pack, so the pack’s rating already includes them. Here’s how I’d do it now.

1. Start with the spa pack’s rating. It’s on the label, the tech sheet or the wiring diagram in the lid. For example, Balboa’s BP601 tech sheet gives a 16A service (20A maximum breaker) or a 32A service (40A maximum breaker). The ACC SmartTouch 1000 I use in the USA is rated 240V, 41A.
2. Check what you’re plugging into it. Make sure the pack can run your equipment at the same time. As a guide, heater current is its wattage divided by the voltage: a 3kW heater draws about 13A at 230V, and a 5.5kW heater about 23A at 240V. Waterway’s 3HP Executive pump draws 10A on high speed at 230V, and the 4HP draws 12A. Blowers vary with size and voltage: the ones Hot Tub Outpost lists range from about 2.4A to 10A. Always use the figure on your own equipment’s label.
3. Set the pack to match the supply. On a smaller supply, the pack switches the heater off while the jets run on high. On a Balboa pack that’s done with the DIP switches. The wiring guide explains how.
4. Add anything with its own feed on the same circuit. This is where things like a separate heat pump come in. Many heat pumps want their own circuit, so check the manual. There’s more in my guide to air source heat pumps for hot tubs.
5. Let your electrician size the breaker and cable for that load, the length of the run, how it’s installed and voltage drop.

A worked example (UK)

A Balboa BP pack with a 3kW heater, a 3HP two-speed jet pump, a circulation pump and a blower. On a 32A supply, the pack can usually run the heater with the jets on high (check the tech sheet for your setup). On a 16A supply, it would have to drop the heater while the jets run. Either way, the circuit is sized from the pack’s service rating, 16A or 32A, not by adding every component together. Total Skills says a 32A supply suits most standard hot tubs up to about 7kW, with 40A for larger units with multiple pumps or bigger heaters.

A worked example (USA)

The ACC SmartTouch 1000 is rated 41A at 240V, and ACC specifies #6 AWG copper conductors. That’s typically wired as a 50A GFCI-protected circuit, which is exactly what most spa panels are set up for. Your electrician confirms it against the nameplate and your local code.

What about cable size?

As a guide, a 32A UK circuit is often 6mm², going up to 10mm² for 40A or a long run. A US 50A spa circuit is usually #6 AWG copper. But cable size depends on the current, the run length, how it’s installed and voltage drop, so it’s your electrician’s calculation, not a rule of thumb. The wiring guide goes into it.

What does it cost?

Prices vary a lot with the length of the run and the state of your existing installation, so treat these as ballpark figures and get quotes.

• UK: Total Skills puts a typical hot tub installation at £400–800, including the circuit, isolator, cable, testing and certification. A long run, a lot of digging or a consumer unit upgrade will push that up.
• USA: HomeGuide gives $800–1,600 for a dedicated circuit, underground conduit and wiring up to 100ft, $100–250 for a permit, and $1,400–2,800 if your electrical panel needs upgrading.

You can save some money by doing the labouring yourself, such as digging the trench and laying the duct before the electrician arrives. Agree it with them first. Then there’s running costs. My tips on bringing those down are in How I saved 66% on my hot tub electricity cost.

Permits, notification and inspection

• England and Wales: the Planning Portal says you typically won’t need planning permission for a garden hot tub (unless you’re in a listed building or conservation area), but the electrics must meet Building Regulations and be installed by a registered competent person. A new hot tub circuit is notifiable under Part P. A registered electrician (NICEIC, NAPIT and so on) self-certifies it and gives you an Electrical Installation Certificate. Keep it safe, as you’ll want it if you sell the house. Scotland and Northern Ireland have their own building rules, so check locally.
• USA: most cities and counties need a permit and inspection for a hot tub circuit, following NEC Article 680 as adopted locally. The inspector will look at the GFCI, the disconnect position and bonding. See Do I need a permit for my hot tub? and What is ground bonding?

When to plan the electrics

Earlier than you think. The supply is connected at the end, but it’s planned at the start:

• Before you dig: decide where the control room goes and how the cable gets there. Get a quote, and check your consumer unit or panel has capacity.
• Before you pour concrete: lay a duct or sleeve under slabs and paths. My groundwork guide covers this.
• While building the control room: leave space and a sensible route for the cable, the isolator and the pack. See Hot tub control room design considerations.
• At the end: the electrician connects, tests and certifies, then you configure the pack.

Your checklist for the electrician

Here’s what to ask your electrical contractor for.

UK

• A dedicated 230V circuit from the consumer unit, rated to the spa pack’s service (usually 32A, sometimes 16A or 40A)
• A 30mA Type A RCD, ideally as a dedicated RCBO
• SWA cable sized for the load, run length and voltage drop
• An IP65 rotary isolator rated for the circuit, within sight of the tub and at least 2m from the water
• A check of the earthing arrangement for outdoor use
• Part P notification and an Electrical Installation Certificate

USA

• A dedicated 240V, 60Hz, 4-wire supply (L1, L2, neutral, ground)
• A breaker sized for the pack’s nameplate (for example, 50A for a 41A ACC pack)
• Copper conductors sized for the load and run (for example, #6 AWG for 50A)
• A GFCI spa disconnect within sight of the tub and at least 5ft from it
• Bonding to NEC Article 680
• A permit and inspection

Common mistakes

• Adding every component’s current on top of the pack’s rating, and ending up with a far bigger (and more expensive) supply than you need.
• Going the other way: a supply too small for your equipment, with the DIP switches set as if it were bigger.
• Trying to run a DIY tub on 120V in the USA.
• Using a Type AC RCD in the UK, or sharing an RCD with house circuits.
• Putting the isolator where it can be reached from the tub, or out of sight of it.
• Forgetting the heat pump when you plan the supply.
• Pouring the patio before the duct is in.

If your tub keeps tripping once it’s running, work through my breaker tripping troubleshooting guide.

Planning your own build?

The electrics are far easier when the control room is planned properly. The Ultimate Hot Tub Control Room Guide covers the layout, and my DIY hot tub plans include the plumbing layout and a full parts list. If your build is custom, I can draw it up as architectural CAD with a 3D plumbing design to hand to your builder, electrician or permit office. Spa packs, pumps and heaters for each country are available from parts4tubs.co.uk in the UK and parts4tubs.com in the USA.

FAQs

What size electrical supply does a hot tub need?

Size it from the spa pack’s rating. In the UK that’s usually a 32A circuit (16A or 40A for some setups). In the USA it’s a 240V circuit, typically 50A for the packs I use. Your electrician confirms it.

Can I plug a DIY hot tub into a normal socket?

No. Some small inflatable tubs run from a 13A socket, but a DIY tub needs a dedicated, hard-wired circuit with RCD or GFCI protection and a local isolator.

Do I need an electrician to install a hot tub?

For the supply, yes. In England and Wales it’s notifiable under Part P and should be done by a registered electrician. In the USA it usually needs a permit and inspection.

How much does it cost to wire a hot tub?

Roughly £400–800 in the UK, and $800–1,600 in the USA for a run of up to about 100ft, plus a permit. Long runs and panel upgrades cost more.

Can a hot tub run on 120V in the USA?

Some small plug-and-play tubs do, but not a DIY block or concrete tub. A 120V 15A circuit gives only about 1.8kW in total. Use 240V.

How far must the isolator be from a hot tub?

In the UK, at least 2m from the water and within sight of it. In the USA, the disconnect must be at least 5ft (1.5m) horizontally from the inside wall of the tub, within sight of it.

Please, please, please get an experienced electrician to do this work. With the currents involved in a hot tub, the consequences of getting it wrong could be extremely costly, and I don’t just mean financially. Got a question about planning your own supply? Drop it in the comments below. I read them all.

Cheers,
Andi

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Hi, Andi here. I own Buildahottub.com and also write all of the articles and info pages on the site. Some years back now, I built my own hot tub but struggled to find the information I needed. So, once my tub was complete, I started this website to help others in their own pursuit of hot tub and plunge pools DIY building information.

Fast forward to 2025, I've helped over 1400+ DIY customers just like you all over the world build hot tubs and pools. Have a good look around the site, there are lots of resources here. Please do get in touch if I can help you. - Cheers, Andi