There are four basic types of hot tubs. The most popular is the above-ground prefabricated hot tub that's typically made from molded acrylic backed by fiberglass or ABS plastic. A cabinet of wood or a durable synthetic lookalike surrounds the tub. Some newer models are made entirely from rotationally molded plastic called rotomold, or "roto" for short. This material is tough, lightweight, inexpensive, and comes in a variety of colors. It's generally used only for smaller tubs that hold a maximum of six people. Still less common are above-ground tubs made of stainless steel, which is attractive and durable but very expensive.
Prices for an above-ground tub can start at $2,000 for a basic rotomold spa and go up to $17,000-plus for a high-end acrylic hot tub with a genuine wood cabinet and lots of features. In addition, above-ground spas must be installed on a level, stable surface like a concrete pad, and some models require a 220-volt outlet. If you already have the necessary electrical outlets, plumbing, and a suitable site, installation costs can be fairly minimal, otherwise all but the handiest of DIYers will need to budget for the services of a qualified electrician, plumber, and mason or contractor.
Above-ground hot tubs are often labeled as portable, and technically they are. A small roto spa can be set up on the deck during the summer and stored in the basement in the winter, according to editors at Spasearch magazine. That said, at 225 pounds and up, these tubs are still fairly difficult to move. A more truly portable option is a soft-sided, inflatable hot tub. Generally made of vinyl, these tubs arrive deflated and can easily be installed on any level surface, indoors or out. Just inflate the tub with the accompanying motor and fill from a hose, then plug in the heater. Vinyl tubs are not only easy to take with you when you move but can also be transported to a party or on a camping trip. They're also by far the least expensive type of hot tub; several models are available online for less than $500.
But there are some downsides with inflatable hot tubs. The vinyl material is easily damaged, and inflatable spas usually rely on blowers rather than the hot water jets found in more upscale choices. The aesthetics of an inflatable hot tub -- think oversized blow-up kiddie pool -- have drawn some catcalls from owners as well.
Wooden hot tubs are the third choice among above-ground spas. These models hearken back to the hot tub's origins as a wooden wine cask. Typically built using redwood, cedar or teak, these spas often have a simple round design with bench seating. Because they're shipped in pieces and assembled on site, they can be carried through doorways and up or down stairs to their final location; bulky acrylic tubs may not fit through narrow spaces.
The appeal of wooden tubs lies mainly in their durable construction and attractive appearance. Although they lack the contoured seating found in other spa types, they tend to be deeper, increasing the amount of legroom and the effects of buoyancy. Because they hold a greater volume of water, however, they're very heavy and must sit on a base of solid concrete or a specially engineered and reinforced deck. Unlike most other hot tubs, wooden tubs may be heated with gas or wood as well as electricity. They generally range in price from $4,000 to $9,500 for a complete system.
In-ground hot tubs are the most expensive because professional installation requires excavation as well as plumbing and electrical work. Total costs range between $15,000 and $20,000. They're typically made of air-blown concrete called gunite or poured concrete, and sometimes have a decorative tile overlay. They may not have as many jets or be as energy-efficient as above-ground tubs, but you can opt for a gas heater to save on long-term energy costs. Because in-ground spas are permanent, they can potentially raise the value of your home. The downside, of course, is you can't take it with you if you move.