Hot tubs tend to come in two main electrical supply options: 13 and 32 amp.
But which should you go for?
In this short guide, we’ll walk you through the difference between the two kinds of home spas, how much the installation and running costs vary, and which is right for you.
What’s the difference between 13 amp and 32 amp hot tubs?
There are number of crucial differences between 32 amp hot tubs and their 13 amp equivalents, including:
The power supply
Of course, the main difference between the two kinds of home spa is the power supply they run on.
13 amp models – known as ‘plug-and-play hot tubs’ – run on a standard three-pronged plug socket, whereas 32 amp hot tubs require a 32 amp electrical supply.
This means a fully qualified and certified electrician will need to install an electrical supply and run an armoured cable to your 32 amp hot tub in order to meet building regulations, which will raise the installation cost by a few hundred pounds.
The biggest functional difference between 13 amp hot tubs and their 32 amp equivalents is that a 13 amp hot tub doesn’t have enough power to run its heater and jets at the same time.
Opt for a plug-and-play hot tub and the heater will automatically cut out when you turn its water jets on full power.
Because spas lose around 60% of their heat through the surface of the water, they can cool down quite quickly without the help of their heater – especially in winter.
Of course, insulation helps a lot here – so if you decide a 13 amp model is the right option for you, be sure to go for a model from a high-end brand that’s fully insulated with top-quality foam.
13 amp hot tubs are also typically restricted to 2kw heaters, while 32 amp models can have 3kw heaters that heat the water much faster. So, you have to wait quite a bit longer – up to seven or eight hours in the depths of winter when the ambient temperature is in the single digits – to use a 13 amp hot tub after refilling it compared to a 32 amp model.
The circulation pump
Some 13 amp hot tubs don’t have a separate 24-hour circulation pump, which means the main water pump will be activated at low speed whenever the temperature of the water needs raising to meet your set temperature (usually 37-39°C)
Whereas the 24-hour circulation pumps that maintain the temperature of 32 amp hot tubs are almost silent, the main water pumps of a 13 amp hot tubs can be a fir bit louder, especially if water is being circulated into the hot tub via massage jets that have moving parts in them. And it will kick in at random times throughout the day and night unless you stump for a model that allows you to control what time of day the pump activates.
If your hot tub is near your house or your neighbour’s, this ambient noise can be a real nuisance – especially if your home spa sits on decking, as extra vibration can be created by the decking structure itself.
When the heater of a 13 amp home spa without a separate circulation pump is activated, the main pump also has to be on (at low speed) in order to push the water through the jets from the heater.
So if relaxing in silence for longer periods of time without the jets running is important to you, a 13 amp spa without a separate circulation pump is possibly not the ideal choice.
The number of pumps
A 13 amp hot tub is limited to either a single two-speed jet pump or a lone jet pump alongside a circulation pump.
The extra amps mean 32 amp models tend to have at least two jet pumps, meaning they can supply all the jets with more power for a more intense massage.
That’s not to say that 13 amp hot tubs don’t provide you with a pleasant hydrotherapy massage, as you can divert the power to a single seat for a more powerful massage and open the air valves to increase the intensity.
However, opt for a 32 amp model and everyone will be able to enjoy a full-power massage at once.
The number of jets
Because it has more power going into more pumps, a 32 amp hot tub can have more jets than a plug-and-play equivalent.
Because 32 amp hot tubs have more pumps and jets and a more complex control panel, they tend to be more expensive than their 13 amp equivalents.
The installation cost
A 32 amp hot tub needs to run through a 32 amp supply with an isolator switch. So, if you don’t already have one of these in your garden you’ll need to have one installed to use a higher-voltage home spa.
A 13 amp spa can run through a standard waterproof RCD-protected three-pronged outdoor socket, shaving a few hundred pounds off the upfront cost of the hot tub.
It will cost around £150-£450 to have a socket installed for a 13 amp spa and up to £750 to have a 32 amp feed installed, meaning it typically costs £300-600 more to install a 32 amp hot tub compared to a 13 amp equivalent.
Of course, a 32 amp model also has better performance. Plus, if you keep your hot tub for a decade, that installation cost breaks down to £30-60 a year – and the feed is already there if you opt for another 32 amp spa as well.
No matter which kind of hot tub you opt for, make sure its electrical outlet is at least two metres away from the hot tub at its closest point.
Also ensure that you connect your hot tub to the power supply with armoured (steel braided SY) cable, making sure trailing cables aren’t causing a trip hazard.
And don’t be tempted to plug in a 13 amp hot tub via standard extension cables running to indoor sockets, as cables that aren’t protected by steel wire armour and RCDs can be extremely dangerous – especially when water is present.
The running costs
Counterintuitively, the difference in hot tub running costs between 13 and 32 amp models is actually negligible.
32 amp hot tubs cost more to run, but 13 amp models need to work harder to make up for the heat that’s lost when the jets are on and get the water up to temperature after its been changed.
How well insulated your spa is, whether you’ve built hot tub housing, and how often you use your spa will all have a bigger impact on your electricity bills than what voltage your tub tub runs on.
However, the maintenance cost of a 13 amp hot tub is likely to be cheaper over time, simply because there are fewer electronics to potentially go wrong.
Finally, it’s slightly easier to relocate a plug-and-play spa, as there are no permanently fixed electrics to worry about. You can simply unplug the spa, drain it, and move it to your new home without having to get a qualified electrician to safely disconnect the electrics.
Are 13 amp hot tubs any good?
So, do we recommend 13 amp spas here at WhatSpa?
There’s no doubt that a 13 amp hot tub from a leading brand is a big step up from an inflatable hot tub or a cheap grey import. It will not only give you a better massage than an inflatable hot tub, but also cost less to run, as it will be much better insulated.
Because they have fewer components and don’t require you to install a specialist power feed, the installation of your hot tub will cost a few hundred pounds less than a higher amperage equivalent.
But the jets won’t give as powerful a massage as a 32 amp model, especially when more than one person is in the spa at a time.
So, if you want a premium experience for you and your guests whenever you slip into your hot tub, then a 32 amp model is the right way to go.
However, a 13 amp hot tub from a reputable brand is a great choice for someone looking for a quality hot tub on a budget and is mainly planning on using their spa for solo soaks.
Whether a 13 amp or a 32 amp hot tub is the right option for you, be sure to buy yours from a WhatSpa? approved dealership to make sure you’re getting a quality spa that’s installed by certified engineers.
And be sure to pick up your free copy of WhatSpa? magazine for help picking the right hot tub for you – not matter what voltage you opt for.
I am the Editor-in-Chief at WhatSpa? Media Group and my job is to keep you informed about the very latest hot tubs on the UK market... the best job in the world! When I'm not being deluged with press releases and hot tub brochures I enjoy keeping fit and participating in endurance events including triathlons and distance running.