Inflatable hot tubs, every US model compared

Slowly: 1–3.5°F an hour by the makers' own figures. The reason is the plug. A 15-amp, 120-volt circuit tops out at 1,800 watts, and the heater has to share it with the pump and blower, so inflatable heaters are 1,300 to 1,350 watts. A hard-shell tub on a 240-volt line runs a 4 kW heater, the median of 272 spec sheets we track.

You can check any heat-up claim with arithmetic. One watt-hour is 3.412 Btu, and one Btu warms a pound of water by 1°F; a gallon weighs 8.34 lb. So Intex's 1,300 W heater can add at most 2.5°F an hour to its 210-gallon tubs and 1.8°F to its 290-gallon ones, before any heat escapes. Intex lists 2–3 and 1.1–2°F.

MSpa lists 2.5–3.5°F an hour for 3 of its 245-gallon tubs (Vito, Soho and Portland). A 1,350 W heater can add at most 2.3°F an hour to that much water, and even the full 12 amps MSpa's US manual lists for its Comfort tubs would add 2.4°F. MSpa doesn't say how it measured. Bestway publishes hours instead: 13–29 hours to reach 104°F when the water and the air start at 68°F, and 23–40 hours from 50°F. Its general FAQ claims 2–3°F an hour on 120 volts. More on the math: hot tub heaters.

Most can't: Intex and MSpa set a 39°F limit, and only Bestway's Freeze Shield model is rated to stay out in freezing weather. Intex says not to use or leave its spas out when the air or the water is 39°F or colder, and its warranty excludes freeze damage. MSpa's US manual gives the same 39°F limit, although every MSpa model has an anti-icing mode that warms the water to 37.4°F when it nears freezing.

The exception is Bestway's SaluSpa Hot Springs. Its Freeze Shield holds the water between 42.8°F and 50°F, so it can stay set up through winter with the heater on, down to 14°F air. The picks for cold weather are on best inflatable hot tubs.

Nobody can say from the specs, because no inflatable maker publishes a standby figure, the power a covered tub uses to hold its heat. What we can work out: the 1,300 W heater costs about 24¢ for every hour it runs at the 18.19¢ per kWh US average (January to July 2026). Warming a fresh 210-gallon fill from 60°F to 104°F takes at least 22.6 kWh, about $4.11, and more in practice because the tub loses heat while it warms.

The standby number does exist for spas sold in California. The state has made makers certify inflatables as their own category since 2018, and since 2019 the energy label for an inflatable goes on the retail box. Read the box before you buy. Hard-shell tubs file the same test: the median is 197 W across 317 tubs. See inflatable vs hard-shell hot tubs and hot tub running cost.

Jacuzzi, which sells hard-shell tubs, puts inflatables at 2 to 5 years against 10 to 15 years for a standard acrylic tub. We found no independent study. The makers' own warranties point the same way: 6 months to 2 years on the tub. Intex's current manuals give 2 years on most PureSpa sets, though an older Intex warranty sheet still on its site says 1 year. The vinyl is the weak point: Bestway warns that sun softens the PVC and raises the air pressure, which can deform the top ring.

Pumps wear out too. In 2024 Bestway recalled about 866,000 AirJet and HydroJet spa pumps sold from May 2021 to May 2024 because they can overheat. For hard-shell lifespans by part, see how long hot tubs last.

It depends on what you need most. The best inflatable hot tubs page picks the largest, the fastest to heat, the best for cold weather and the one with the most jets, on published figures only. If you're weighing an inflatable against a rigid tub, inflatable vs hard-shell hot tubs compares heat, running cost and lifespan, and plug-and-play hot tubs lists the hard-shell tubs that also run on 120 volts.