How long does a hot tub take to heat up? From a cold fill in Ireland, an acrylic hot tub usually takes 12–24 hours, an inflatable 24–48 hours and a wood-fired tub 2–4 hours. After that, a good hot tub stays hot all the time, so you can use it whenever you like.
Hot tub heat-up times
| Hot tub | Heat rate | Cold fill to 38°C |
|---|---|---|
| Acrylic, 3 kW heater | 3–4°C per hour | 12–18 hours |
| Acrylic, 2 kW heater (13A) | 2–3°C per hour | 16–24 hours |
| Inflatable | 1–2°C per hour | 24–48 hours |
| Wood-fired | 8–12°C per hour | 2–4 hours |
Why it takes so long
A hot tub holds 800–1,500 litres of water, and mains water in Ireland is often only 8–12°C. Heating that much water by around 28°C takes a lot of energy, and the heater is limited by your electrical supply. That’s why a 32A tub heats faster than a plug-in one.
How to heat a hot tub faster
- Keep the insulated cover on and clipped down.
- Fill on a mild day and keep the tub out of the wind.
- Run the jets or pump on circulation so heat spreads evenly.
- Check the filter is clean so water flows freely.
Should you leave a hot tub on?
Yes. Once it is hot, keeping it at temperature costs far less than reheating from cold each time. In fact, most owners leave it at 37–38°C and drop it a few degrees when away. For more, see our guide to hot tub running costs and SEAI’s energy-saving advice.
Frequently asked questions
How long does a hot tub take to heat up from cold?
Usually 12–24 hours for an acrylic hot tub in Ireland, longer for an inflatable.
Can I use a hot tub before it is fully heated?
Yes, it is safe, but it will feel cool. Most people wait until it reaches 36–38°C.
Is it cheaper to leave a hot tub on all the time?
For most well-insulated tubs, yes. Reheating from cold uses more energy.
Why is my hot tub heating so slowly?
Common causes are a missing or worn cover, a dirty filter, cold weather or a 13A supply.
Hot tubs that heat fast and stay hot
Fully insulated hot tubs delivered across Ireland.
