How long before my hot tub warms up
Xavier LabelleThis depends on the temperature of the water from the time you start heating your hot tub and how hot you are expecting the temperature to reach. It will also depend on how powerful your heating element is for the hot tub.
Typically you can expect about 1-2 degrees an hour. Leave the cover on the tub when heating it up. If you leave the cover off, a lot of heat can escape. If the temperature isn’t rising at all, see our guide to fixing a hot tub that isn’t heating.
For example a 1000 litre Hot Tub with a 1.5kW heater, with summer temperature mains water should take about 24 hours. Bigger spas, different heaters and winter mains water will all have longer or shorter heating times.
The quick answer by model
The figures below are a theoretical best case. They show the energy needed to lift each tub from 10°C mains water to 38°C, a rise of 28°C, divided by the heater rating. They ignore heat lost through the cover and cabinet, so real heat-up times are longer. Treat them as a floor, and use the 1 to 2 degrees an hour rule above for planning.
| Model | Water | Heater | Supply | Energy for a 28°C rise | Best-case heat-up |
|---|---|---|---|---|---|
| Yukon | 350 L | 2 kW | 13 amp | 11.4 kWh | about 6 hours |
| Manitoba | 550 L | 2 kW | 13 amp | 17.9 kWh | about 9 hours |
| Calgary and Montreal | 700 L | 2 kW | 13 amp | 22.8 kWh | about 11.5 hours |
| Winnipeg | 905 L | 3 kW | 32 amp | 29.5 kWh | about 10 hours |
| Toronto | 1,000 L | 3 kW | 32 amp | 32.6 kWh | about 11 hours |
| Niagara | 1,465 L | 3 kW | 32 amp | 47.7 kWh | about 16 hours |
Two things stand out. A small tub on a 2 kW heater can warm up as fast as a big tub on a 3 kW heater, because there is less water to heat. And the jump from a 2 kW plug-in model to a 3 kW hard-wired one matters less than the volume of water you are heating.
How the season changes things
Mains water in the UK is noticeably colder in winter than in late summer, and a cold, windy night pulls heat out of the cabinet and cover while the heater is working. In practice that means:
- Late spring to early autumn: the fill water is warmer, so the rise to bathing temperature is smaller. A first heat-up overnight is common for smaller tubs.
- Winter: the starting temperature is lower and heat loss is higher. Allow at least an extra day for a large tub, and plan a refill for a mild spell where you can. New to hot tubs this winter? Our autumn and winter buying guide covers the first fill and heat-up.
- Day to day: once the tub is up to temperature it only has to replace what it loses, so reheating after a soak is quick compared with the first fill.
One owner of an Okanagan reported a 24°C rise in about 7.5 hours, costing roughly £2.40. That is a single customer's experience on a 700 litre, 2 kW tub, not a guaranteed figure, but it shows what a well-covered tub can do in good conditions.
What slows heating down
- The cover is off or not sealing. Most heat escapes from the water surface. A cover that is waterlogged, split or not strapped down loses much more. Our guide to how a good cover cuts energy costs explains why.
- A dirty filter. The heater needs a good flow of water through it. A clogged cartridge reduces flow and can stop the heater switching on. See how often to clean your filter.
- Running the jets with the cover open. Jets and air controls mix air into the water, which cools it quickly. Keep them off while you wait for the tub to heat.
- Wind across the tub. An exposed spot loses heat faster. A fence, hedge or shelter on the windward side helps.
- Not enough power at the socket. A plug-in model needs the full 13 amps available at the socket. A shared circuit, an extension lead or another heavy appliance on the same supply can cause problems.
- Low water level. Fill to about 25 mm above the waterline. Too little water and the system can struggle to circulate properly.
How to speed up the first heat-up
- Fill through the filter housing to reduce trapped air, then check for leaks before you start heating.
- Put the cover on straight away and fasten the straps.
- Set the target temperature on the topside panel and leave the tub alone. Opening the cover to check every hour lets heat out.
- Fit the cover in a sheltered spot or add a temporary windbreak if it is a cold, blustery day.
- Balance the water as it warms. If the water is still below 20°C, dissolve chlorine granules in a bucket of water before adding them.
13 amp and 32 amp heaters compared
Our plug-in models, such as the Yukon, Montreal, Calgary, Manitoba and Okanagan, use a 2 kW heater and run from a 13 amp outdoor socket. The larger hard-wired models, including the Winnipeg, Toronto, Victoria and Niagara, use a 3 kW Balboa heater on a dedicated 230V, 32 amp supply with its own RCD, fitted by an electrician.
A 3 kW heater puts in half as much heat again each hour as a 2 kW one, but those tubs also hold more water. That is why the best-case times in the table end up fairly close. Where the bigger heater does help is recovery: after a long soak with the cover open, a 32 amp tub tends to climb back to temperature with less waiting. If you plan to use the tub most evenings with several people, that is worth weighing up. Our 13 amp plug and play range suits most couples and small families who soak a few times a week.
Planning the first fill: a worked example
Say you take delivery of a 700 litre Calgary on a Wednesday and want to use it on Saturday afternoon. A sensible timeline looks like this:
| When | What to do |
|---|---|
| Wednesday evening | Check the base is level, connect to the 13 amp socket, fill through the filter housing to about 25 mm above the waterline |
| Wednesday night | Check for leaks, set the temperature, fit and strap the cover |
| Thursday | Leave it alone. Test and start balancing alkalinity and pH once the water is warming |
| Friday | Water should be close to temperature. Add sanitiser and bring chlorine to 1.0 to 1.5 ppm |
| Saturday | Test again, then enjoy the first soak |
That leaves plenty of slack for a cold week or a windy garden. The same plan works for larger tubs if you add an extra day.
What heat-up costs
To estimate the cost of the first heat-up, take the energy figure from the table and multiply by your unit rate. At an illustrative 25p per kWh:
| Tub size | Energy for a 28°C rise | Approximate cost at 25p/kWh |
|---|---|---|
| 350 L | 11.4 kWh | about £2.85 |
| 700 L | 22.8 kWh | about £5.70 |
| 1,000 L | 32.6 kWh | about £8.15 |
| 1,465 L | 47.7 kWh | about £11.90 |
Real costs will be higher because of heat lost along the way. Your unit rate is on your bill, and Ofgem's price cap page shows the current typical rates. After the first fill, the day-to-day cost is about keeping the water warm, which depends far more on the cover and how often the lid is open.
Warm-up FAQs
Should I turn the tub off between uses to save money?
Usually not. Reheating from cold takes many hours and a lot of energy, so most owners keep the tub at temperature or lower it by a few degrees if they are away for a short while.
Why does my tub heat more slowly than the table shows?
The table ignores heat loss. Cover condition, wind, a dirty filter and cold weather all add time.
Can I use the jets while it heats up?
You can, but it slows things down if the cover is open. Keep the cover on until the water reaches the temperature you want.
What temperature should I set?
Our tubs can be set between 26°C and 40°C. Most people soak at around 37°C to 38°C.
The temperature is not rising at all. What should I check?
Check the filter, the water level and the display for error codes, then work through our not-heating guide. If you are still stuck, call us on 01293 824094.
For further information call Canadian Spa on +44 (0)1293 824094
Choosing a hot tub?
Compare our hot tubs and swim spas, or visit our showroom near Gatwick.