Types of hot tubs

Short answer

Hot tubs come in three builds: an AcrylicThe hard, glossy plastic sheet that forms the surface of most hot tub shells. It is heated and formed over a mold, then backed with fiberglass or plastic for strength.In the glossary shell inside a frame and cabinet, a one-piece RotomoldedA one-piece plastic hot tub made by fusing plastic powder into a single wall inside a heated mold. The shell and the outside are the same piece.In the glossary plastic tub, or an Inflatable hot tubA vinyl ring you blow up, with a separate pump-and-heater unit. It runs on a small 120V heater, so it heats slowly.In the glossary . Most are acrylic: 277 of the 333 spec sheets we track that name a shell. Acrylic tubs are heavier, carry longer warranties and mostly need 240V; the other two are lighter and mostly plug in.

Updated October 2026By the HotTubFinder research desk

Acrylic, rotomolded and inflatable hot tubs compared: a backed acrylic shell in a frame and cabinet, one hollow plastic piece that plugs in, and a vinyl ring with a separate pump-and-heater unit — Acrylic, rotomolded and inflatable hot tubs side by side.

The three types at a glance

Acrylic277 of 333 tubs	800 lbmiddle tub	10 yearsmiddle tub	Mostly 240V43 can plug in
Rotomolded15 of 333 tubs	390 lbmiddle tub	5 yearsmiddle tub	Mostly 120V13 of 15 plug in
InflatableIntex, Bestway and others	74 lbmiddle tub	2 years or less	120V, 1,300 W heater

Weight and warranty are for the middle tub of each type in our data; the inflatable heater and warranty are from Intex's spec sheet and manuals.

How is an acrylic hot tub made?

Shell layers: an acrylic skin backed by fiberglass, self-supporting compared with propped on posts

A flat acrylic sheet is heated until soft, pulled down over a mold by vacuum, then backed with resin and fiberglass for strength. What matters is what holds that shell up once it is full of water and people. A Self-supporting shellA shell with enough fiberglass built up behind the acrylic to carry the water and the people on its own, with no posts or foam holding it up.In the glossary could be lifted out of its cabinet, set on concrete, filled and sat in, and it would hold its shape. Others lean on a frame or on foam, and over the years a shell that flexes can crack around the jets. See self-supporting hot tub shells for how to check one in a showroom.

What is a rotomolded hot tub?

Rotational molding turns plastic powder inside a heated mold so it coats the inside and forms one hollow part: here, the shell and cabinet in one. In our data the rotomolded tubs are Caldera Spas Fantasy, Hot Spring Freeflow and Master Spas Getaway: 15 models, 2 to 5 seats, a median 390 lb dry against 800 lb for acrylic tubs. Warranties are shorter: the median rotomolded tub carries 5 years on the shell structure, against 10 for acrylic.

Inflatable vs real hot tub: what's the difference?

Heat, cold and coverage. Intex's 120V PureSpa models use a 1,300 W heater, and Bestway says its tubs warm about 2 to 3°F an hour and top out at 104°F. A hard-shell tub on 240V runs a 4 to 5.5 kW heater. Inflatable warranties run 2 years or less. Every inflatable, with heater, heat-up and warranty, is on inflatable hot tubs; if you want a tub that plugs in but lasts longer, see plug-and-play hot tubs.

The details

Which brands build which type, and the warranty fine print.

Shell material by brand

15 brands

Shell material and whether the shell supports itself, by brand

American Whirlpool	Acrylic6 acrylic	PartlyNot foam-filled, but the frame and base carry the load.
Artesian Spas	Acrylic38 acrylic	PartlyFiberglass-backed shell, but a wood frame and foam share the load.
Bullfrog Spas	Acrylic21 acrylic	NoNo. A molded ABS frame carries the water weight, not the shell.
Cal Spas	Acrylic57 acrylic	PartlyFoam is an upgrade, so the shell holds up unfoamed.
Caldera Spas	Acrylic, rotomolded polyethylene18 acrylic, 5 rotomolded	PartlyFantasy shells stand alone; acrylic models lean on a frame.
Dimension One Spas	Acrylic or UltraLife polymer15 acrylic	NoNo. A wood frame carries the shell, per D1's own warranty.
Hot Spring	Acrylic, rotomolded polyethylene19 acrylic, 5 rotomolded	PartlyFiberglass-reinforced shell, but Watkins says the frame carries the load.
Jacuzzi	Acrylic8 acrylic	Not publishedJacuzzi doesn't publish this. Ask the dealer.
Marquis	Acrylic25 acrylic	YesHand-rolled fiberglass shell that holds the water on its own.
Master Spas	Acrylic, rotomolded polyethylene20 acrylic, 5 rotomolded	YesA fiberglass-backed shell that holds its own shape and water load.
Nordic Hot Tubs	HDPE plastic (Nordic Permashell)26 hdpe	Not publishedNordic Hot Tubs doesn't publish this. Ask the dealer.
PDC Spas	Acrylic14 acrylic	YesYes. The fiberglass shell stands without foam or a frame.
Sundance Spas	Acrylic4 acrylic	NoNo. A base pan and a separate frame hold it up.
Vita Spa	Acrylic20 acrylic	PartlyFiberglass-backed shell, but a wood or steel frame carries it.
Wellis	Acrylic27 acrylic	NoNo. A polymer frame and ABS base carry the tub.

“Self-supporting” is one of our 8 build checks, judged from each maker's own documents.

Most brands we track build only acrylic tubs. Nordic uses its own HDPE plastic shell, Dimension One offers a textured UltraLife polymer on some colors, and three brands add a rotomolded line. If the word “Jacuzzi” is part of what you are comparing, see hot tub vs Jacuzzi.

Rotomolded warranties, in detail

Hot Spring's Freeflow Monterey plugs into a 115V outlet, uses a 1,000 W heater on that supply and weighs 425 lb dry, with 5 years on the structure and 1 year on plumbing and components. AquaRest, a rotomolded brand outside our catalog, gives 5 years on the shell, 1 on equipment and 90 days of labor. Caldera's Fantasy warranty notes that slight flexing of its rotomolded structure is cosmetic.

Inflatable warranties and cold limits

Bestway's FAQ says its spas can't be run below 39°F outside, though its manual rates the SaluSpa Hot Springs, which has Freeze Shield, down to 14°F. Intex's current manuals give 8 of its 11 sets 2 years, for the original buyer only and with freeze damage excluded, and 1 year on the SimpleSpa; an older Intex warranty sheet still on its site says 1 year. Bestway gives 365 days on the pump and 180 days on the liner.

Common questions

Is an acrylic or a rotomolded hot tub better?

Acrylic tubs are bigger and carry longer warranties: a median 10 years on the shell structure against 5 for rotomolded tubs in our data. Rotomolded tubs are lighter (median 390 lb dry) and mostly plug into a 120V outlet.

What is a rotomolded hot tub?

A tub whose shell and cabinet are one hollow piece of polyethylene, made by spinning plastic powder inside a heated mold. They are light, usually plug-in, and carry shorter warranties than acrylic tubs.

Is an inflatable hot tub as good as a real hot tub?

It does a different job. Inflatables heat slowly on a small 120V heater, stop at 104°F, and carry warranties of 2 years or less; Bestway's FAQ says its spas can't run below 39°F outside, though its Freeze Shield model is rated to 14°F.