Running costs updated 1 October 2026. Every electricity figure on this page is costed at the Ofgem price cap average electricity unit rate of 26.32p per kWh, which applies from 1 October to 31 December 2026. Your own tariff may be higher or lower, so check your latest bill before relying on these numbers.
What goes under an inflatable hot tub matters more than most buyers expect. A filled 4-6 person tub weighs around a tonne once people are in it. Get the base wrong and you risk a punctured floor, a lopsided tub that strains its seams, or heat leaking into the cold ground all winter.
Always follow your manual. This guide gives general UK guidance, drawn from manufacturers' instructions and standard water-care practice. It is not a substitute for your hot tub's own manual or for a qualified electrician. Where the two disagree, your manufacturer's instructions win.
The short answer
Put it on a flat, level, solid surface: a paved patio or concrete pad is ideal. Then add an insulated ground mat or interlocking foam tiles on top to protect the floor and cut heat loss. Avoid bare grass, gravel and most garden decking unless it has been checked for the load.
How heavy is a filled hot tub?
| Size | Typical water volume | Rough total weight with bathers |
|---|---|---|
| 2-4 person | About 600-800 litres | About 0.8-1 tonne |
| 4-6 person | About 800-1,000 litres | About 1-1.3 tonnes |
| 5-7 person | About 1,000-1,200 litres | About 1.2-1.5 tonnes |
One litre of water weighs 1kg. These are rough figures. Check your model's stated water capacity.
Surfaces compared
| Surface | Verdict | Why |
|---|---|---|
| Paved patio or concrete pad | Best | Strong, level and easy to sweep clean. Add a mat for insulation |
| Purpose-built hot tub base or level paving slabs on compacted sub-base | Very good | A good DIY option if you have no patio |
| Garden decking | Only if checked | A tonne-plus spread over about two square metres is far more than typical decking is built for |
| Artificial grass on a level base | Acceptable | Fine only if the ground beneath is firm and level |
| Bare lawn | Avoid | Uneven, soft when wet, kills the grass and lets cold and damp in |
| Gravel or stones | Avoid | Sharp edges can puncture the floor |
| Indoors or in a garage | Possible | Needs a floor drain or a plan for splashes, plus good ventilation for humidity |
What to put on top: mats and tiles
- Insulated ground mat: sold by most hot tub brands. It protects the floor and adds a layer of insulation.
- Interlocking foam tiles: cheap, thick and easy to cut to size. Many owners put these under the brand mat for extra insulation.
- Avoid: old carpet (it holds water and rots) and anything with sharp fixings.
Insulation underneath matters more than people think. Heat escapes downwards into cold ground, especially from October to March. That shows up on the electricity bill. See how much a hot tub costs to run.
Before you choose the spot
- Power: you need an outdoor socket protected by an RCD, close enough to reach without an extension lead. Most manufacturers forbid extension leads. If you need a new outdoor socket, use a qualified electrician.
- Drainage: you will empty it every one to three months, so think about where 800-plus litres will go.
- Shelter and privacy: a fence or wall cuts wind chill and heat loss.
- Trees: leaves and sap mean more cleaning.
Next step: how to set up an inflatable hot tub.
The BestPicks UK hot tub guides
Choosing one
- Hot tub buying guide
- Are inflatable hot tubs worth it?
- Lay-Z-Spa vs CleverSpa
- Inflatable vs hard-shell hot tub
- How long an inflatable hot tub lasts
Setting up
Running and looking after it
- How much a hot tub costs to run
- Hot tub chemicals for beginners
- How often to change hot tub water
- Should you empty a hot tub over winter?
- Using a hot tub in freezing weather
Compare models in our best hot tubs UK guide, or work out your bill with the hot tub running cost calculator.
Frequently asked questions
Can I put an inflatable hot tub on grass?
It is not recommended. Grass is rarely level, goes soft when wet, and lets heat and damp in. If you must, level the ground and lay a firm base and an insulated mat first.
Can I put a hot tub on decking?
Only if the decking has been checked for the load. A filled 4-6 person tub with bathers can weigh well over a tonne, which is far beyond what typical garden decking is designed for.
Do I need a mat under an inflatable hot tub?
Yes, it is strongly recommended even on a patio. It protects the floor from abrasion and reduces heat loss into the ground.
Can I put an inflatable hot tub on gravel?
Avoid it. Gravel shifts and its sharp edges can puncture the floor. Lay slabs or a concrete pad instead.
