Hot tub electrics are essential. If you plan to heat your hot tub with an electric heater, you will need electricity. Sounds obvious, right? However, in most instances, it isn’t as simple as just plugging into an outlet. You’ll need a dedicated electrical supply for your hot tub. But what does that look like? In this article, I’ll break down the electrical requirements for your hot tub and explain what you need to know.
Dedicated Breaker for your Hot Tub
When planning your hot tub’s electrics, it’s important to consider the electrical requirements. In most cases, this is a task that requires a professional. Attempting it yourself can be dangerous and may even void your insurance. That said, it’s important to understand what you need to ask your electrician to do.
Firstly, it’s highly recommended that you have your own dedicated breaker. This means that your fuse board should have a specific fuse solely for your hot tub. If the hot tub trips the fuse and turns off, the rest of your house will remain unaffected—which is exactly how it should work.
The size of the breaker or fuse depends on the electrical components inside your hot tub—and we’ll cover that later in this article.
Dedicated Outdoor Rotary Switch
During the planning stage of your hot tub installation, you should consider where to place the outdoor rotary switch. This switch is crucial, as it allows you to quickly shut off power to your hot tub in case of an emergency—making it a key component of hot tub electrical safety.
It functions as a simple rotary on/off switch but must be installed more than 2 metres (6 ft) away from the hot tub to prevent users from touching it while in the water.
The electrician should install a suitable weatherproof block connector at the end of the cable from the isolator. The hot tub’s power supply can then be directly hardwired into the weatherproof block connector inside the hot tub. To prevent water ingress, waterproof gland packs must be used on all electrical connections (including two at the isolation switch). Ensure that all earth cables are clearly marked with green/yellow insulating tape or an earth sleeve.
The required size or current rating (in Amps) of the switch will depend on the electrical components inside your hot tub.
Outdoor Cable for Hot Tub Electrics
When installing a cable from your fuse board to your rotary switch and then to your control panel, you need to ensure that you are using the correct gauge and type of cable.
To deliver the correct amount of current without overheating the cables, you should use a minimum of 10mm² cable, as this is rated for up to 65 amps.
The “10mm²” measurement refers to the cross-sectional area of the individual live or neutral wires, not the combined area of all conductors. This distinction is crucial—if you install wires that are too thin and draw too much current, they can overheat and, in extreme cases, even melt! This is why a qualified electrician is essential. You should request cables rated for at least 65A.
Armoured Cable
If you are running cables outside, for safety reasons, they must be armoured. This protective layer prevents accidental damage, such as a garden spade cutting through the cable and causing an electric shock.
In my case, I chose to attach my armoured cable along the length of my garden wall. (The alternative is to bury it, but it must be at least 2 feet deep—which requires a lot of digging.) I opted for the wall-mounted approach and selected 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 the investment for peace of mind.
What Voltage and Frequency Do I need?
Regarding voltage and frequency, you must ensure that you are supplying the correct amount of electricity (current) at the appropriate voltage and frequency that your heater and pumps are designed for.
For example, in the UK, the voltage standard is 240V at 50Hz, while in the USA, the standard outlet provides 110V at 60Hz.
What I am emphasising here is that you cannot take a heater from the UK, plug it into a USA supply, and expect it to work. But don’t worry— all the pumps and heaters that we supply are specifically designed for the country in which they will be used!
Also, when it comes to pumps, the frequency determines the rotation rate, which is directly linked to power. A component operating at 50Hz spins 20% slower than one running at 60Hz. So, a 50Hz pump running on a 60Hz supply would rotate 20% faster than its intended design, leading to overheating. This is why pumps must be designed for the correct frequency.
I’m in the USA and being told I need a 240V Supply – is that correct?
Yes, this is correct. To run a Hot Tub in the USA you are going to need 240V @ 60Hz.
You may see if you Google around pumps and heaters that are rated at 110-120V, 60Hz. To be honest, trying to take a short cut here and not making the right adjustments in your electricity supply is not going to work. Spa Packs (heaters) and pumps that will run on 110-120V are just not powerful enough. At 120V, you will only get something like 1.4KW of power to heat your Hot Tub which is not enough. Switch that over to 240V and it will now provide you with 5.5KW of power which is more more useful to heating your Hot Tub.
Don’t Worry, the chances are you already have 240V into your home!
- What this means for your Hot Tub supply is that you can take a feed from your main consumer unit/meter from 120V L1 (line/hot 1) and 120V L2 (line / hot 2) which supplies a total of 240V @ 60Hz which is what you need. Some domestic appliances do this already like cookers and washing machines that need more power. The red circle above shows hot this outlet for our Hot Tub would be wired to get 240V.
- Your electrical contractor will be able to tell you more about this. In summary, the chances are you already have the 240V supply that you need into your home and your electrical contractor just has to wire this up correcty for your Hot Tub.
Why Do I need 240V?
How do I calculate the amount of Current that I need?
- Your blower might draw 5A on full speed (we add that to the 20A + 5A)
- Your Spa Pack on full heat might draw 32A (we add this to the 20A+5A+32A)
- Anything else that you have connected to that supply will all draw current. Lights, TVs, Stereos, you need to add these onto this number.
Check List for your Hot Tub Electrical Supply
- 240 V Supply @ 60Hz
- 60-65A Fuse / Breaker
- 60-65A Rotary Switch / Isolator
- 10mm core Armoured Cable (capable of delivering 65A of current)
Final Thought
Please, please, please get an experienced electrical contractor to handle this work for you. If you get it wrong, with the high levels of current involved in a Hot Tub setup, the consequences could be extremely costly — and I don’t just mean financially.
Happy Tubbin’!
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.
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