How to buy the best hot tub: hard shell, inflatable or wood-fired - Grand Designs Magazine

How to buy the best hot tub: hard shell, inflatable or wood-fired

Unwinding in a hot tub is a dream that many of us have, and with our advice you can find the perfect model regardless of budget or garden size.

By Mary Richards |

Whether you want a hot tub for relaxing in, or one for keeping the kids entertained (or both), getting the right model for you and your garden can seem complicated and difficult. Talking to the experts, we’ve got the lowdown on what you need to do before you make the plunge.

Ryan Maskell, of Mask Plumbing Solutions, says, “There are three main types of hot tub: inflatable, acrylic [hard] shell, and wood-fired models. Each type caters to different preferences and budgets, offering varying features and durability. For example, inflatable ones stand out for their affordability and portability. However, they usually lack the durability of acrylic shell and wood-fired models, which offer better insulation, but require more maintenance in the long run.”


Hard shell tubs

Your first choice is to pick the kind of hot tub that you want, which comes down to price, looks and flexibility. Hardshell tubs are designed for permanent installation and have solid walls. They’re more durable than inflatable types, can have insulation in their walls to help keep heat in and reduce running costs, and many are suitable for all-year-round use. Their designs also opens them to more choice, with a wider range of seating options, lights and jets.

Acrylic hot tubs are solid, electrically powered models containing moulded seats or loungers and plenty of water jets, available from companies such as Platinum Spas and Jacuzzi. This kind of tub is suitable for permanent installation and will cost between £5,000 and £25,000 depending on its size, functionality and quality.

For a different solid option, wooden hot tubs are some of the best looking, available from companies such as Ceda and Riviera. These can be either simple solid wooden tubs – often made from sweet smelling cedar wood – or wood-clad acrylic or fibreglass tubs. This kind of tub has a slightly higher starting price, and will cost you between £7,000 and £15,000, depending on the style and features.

Inflatable hot tubs

Inflatable hot tubs, such as those made by Lay-Z-Spa, are a relatively cheap way to enjoy the hot-tub experience. They inflate using their own pump, which also acts as the heater that pump shot air around, and can be plugged into a standard outdoor power socket. More expensive models have slimmer side walls. They can be bought for as little as £200, so are a cheaper entry point. As they deflate, this kind of tub can be taken down and stored during winter, letting you reclaim some garden space when you don’t need or want the hot tub.

Technically, inflatable hot tubs are transportable and can be moved around, although you still need to follow the installation rules (below) and install them on a solid, flat base.

This type of hot tub tends to be round and has a padded bottom that you can sit on. Inflatables are less durable than tubs with solid walls, not as well insulated, and many models aren’t suitable for year-round use. You also get less choice when it comes to lights, jets, and seating.

Wood-fired hot tubs

Wood-fired hot tubs cost roughly between £2,500 and £7,500 and have a small firebox attached where wood is burned to heat the water. Usually these have a tall chimney to take away the smoke. They are ideal for off-grid locations where there is no mains power. This kind of tub won’t have a temperature control on it, and water heat depends on how hot the stove gets. Unless you have electricity nearby, you won’t have jets, either. However, these tubs tend to be cheaper to run.

Where can I install a hot tub?

Regardless of the type yo choice, all hot tubs need to be placed on a flat, stable, hard surface – concrete, paving or even hard-packed gravel are fine. Decking might be OK – it depends how strong it is and how heavy your hot tub will be when full. But you can’t put a hot tub directly on to grass.

Ryan Maskell says, “Tubs should be placed on a stable, level base, with strong foundations. You’ll also need access to water and drainage. Make sure the model’s power needs are being met, without creating a potential safety hazard. If in doubt, always consult the manufacturer’s instructions and guidelines.”

Most hot tubs, bar the basic inflatable models, will need to be installed by a qualified electrician. They don’t need to be plumbed into mains water though, you just use a hose to fill them up. Give some thought to how you are going to get the hot tub into its final position when it is delivered.

It takes several hours for the water in a hot tub to heat up to the right temperature. It’s a good idea to position your tub in some kind of shelter, such as a gazebo. This will provide some privacy, and protect bathers and the water from wind chill.

What size hot tub should you get?

Gareth Ward, from Platinum Spas, says that, when choosing a hot tub, “A good starting point is to look at sizes and how many people can fit in them. Smaller tubs can start with three people, however, the larger tubs can fit eight. It depends on what you want it for: whether it’s for social events, or for personal self-care and relaxation.”

The more people the tub will take, the more room it will take up, so plan carefully to make sure that you don’t buy a tub too big for your garden. It’s worth looking at the dimensions of your ideal hot tub and then marking out the area in your garden, so that you can visualise how much space you’ll have to devote.

Style of seating

Gareth continues, “Then there are hot tubs with normal seating or with loungers – a lounger is an area within a hot tub where people can lie with their feet up and head back, which is arguably the most comfortable way to enjoy the hot-tub experience.

Extra features

“As well as this, hot tubs include different features, from different hydrotherapy jets and massage settings, to lighting and LED effects, built-in speakers and more. I would recommend going into showrooms to test out hot tubs, as there are so many different specifications and types. It’s worth trying a range to find out which suits you and your needs the best.” Some hot tubs can be controlled remotely via an app, which means you can start them heating up, so that they’re ready for when you go outside.


The temperature in a hot tub (typically 36-38°C) isn’t high enough to kill bacteria that thrive in warm water. Some of these, such as legionella and E coli are potentially very hazardous to health. But they can be kept in check with a rigorous water-sanitising and tub-cleaning routine. This means there’s a lot of work involved in owning a hot tub. And it’s vital you do this work to keep the water in your hot tub hygienic and safe.

You’ll need to clean the tub and its filter regularly. And you should test the water every day to check the pH level of the water and level of sanitising chemical. The sanitising chemical – chloride or bromide depending on your tub – needs to be added to the water every day. And the tub should be drained and cleaned with pipe-cleaning solution every month or so. You might find it easier to get a submersible pump to help with this.

You will also need to ‘shock’ the water every so often. This means adding a small amount of oxidising agent to the water to kill bacteria, break down chloramines and remove organic compounds. You will need to do this more or less frequently depending on how many people use your tub and whether they shower before getting in. It’s really important you follow the specific maintenance routine recommended by your hot-tub manufacturer.

If you’re not going to use your hot tub during the winter, you need to winterise it by draining all the water out and cleaning it thoroughly.

Health hazards

As well as the hazards from bacteria, which should be dealt with by a good tub-hygiene routine, there are other health problems that can be associated with hot tubs. Pregnant women shouldn’t use them, and anyone with breathing difficulties or high blood pressure is advised to proceed with caution.

It’s recommended that children under eight don’t go in hot tubs. Older children should be tall enough that their head is out of the water when they stand up, and they need to be supervised at all times. Children shouldn’t stay in the water for extended periods.


Although the wood-fired hot tubs look super cool and are great for an off-grid location, burning wood does, of course, generate carbon dioxide and particulates. Neither of which are very environmentally friendly. Choose kiln-dried logs (from sustainably managed woodland) for the cleanest burn.

Electric tubs are cleaner at the point of use, though, ultimately, electricity is only as clean as the power source used to generate it.

Several companies now sell air-source heat-pump compatible hot tubs, and heat pumps designed to be fitted to existing hot tubs. There is a significant upfront cost involved, but a heat pump will work much more efficiently than a standard electric hot-tub heater, reducing energy use and the tub’s carbon footprint. Savings could run to £500 a year, but it’s important to take advice to find a well-insulated tub that has pipework that is compatible with a heat pump.

In terms of fabrication, wood, from sustainably managed forest, is a renewable resource, while acrylic is made from petroleum, a non-renewable fossil fuel. In its favour, the process used to make things like hot tubs from acrylic is relatively efficient, and the resulting products are durable. Acrylic can be recycled, but, at the moment, it is hard to find places that accept individual items for recycling. Some companies are looking at ways to reuse their hot tubs. Jacuzzi, for example, sells reconditioned hot-tubs.

One of the most important things to look for is how insulated a hot tub is, because this will play a big part in its energy efficiency. Some manufacturers, such as Penguin Spas, give their tubs an R rating that indicates how well-insulated they are. The higher the R number the more insulated they are, which means you need less energy to maintain a constant temperature.

Renson Camargue Louvered Canopy by Garden House Design in Sussex

Energy use

There are lots of ways you can reduce your energy you use:

  • choose a well insulated tub, which will help maintain water temperature for longer
  • consider going for a heat-pump-powered tub
  • use a well insulated, well fitting cover to keep the heat in. An insulating blanket that sits on the surface of the water will help too
  • turn the temperature down a couple of degrees. You shouldn’t have your hot tub any hotter than 40ºC for health reasons and 35ºC is the recommended temp if you’ll have children in it
  • if you use your hot tub regularly, leave it on rather than turning it off, as this will likely use less energy than turning it off then having to reheat the water from scratch when you want to use it again. Just turn the temp down a little to, say, 30ºC, then turn it up again before you want to get in
  • wind-chill will have a significant cooling effect on the hot water, so site your tub in a shelter or at least beside a fence, out of the wind
  • turning the jets on to circulate the water will help the tub heat up quicker

Running cost

Running costs for your spa will depend on many factors including its size, how well insulated it is etc. WhatSpa has calculated that the annual costs of running a hot tub, including electricity, chemicals, servicing and so on is £800 – £1,075 a year.