If you are specifying a residential steam generator and performance, consistency, and long-term reliability are priorities, the ThermaSol PRO Series III is the benchmark the rest of the market is measured against. It is the only steam generator in the world with ThermaSol's patented Smart Steam technology, the only one with the PowerFlush automated cleaning system built in, and the only one in the residential category backed by a no-questions-asked lifetime warranty. This guide covers every model in the lineup, how to size correctly, and what separates the PRO Series III from the competition.
TheSteamStore.com is an authorized ThermaSol dealer. Browse the complete PRO Series III collection or contact our team for sizing help.
What makes the PRO Series III different
Three technologies set the PRO Series III apart from every other residential steam generator on the market — and two of them are exclusive to ThermaSol.
Smart Steam technology (patented, ThermaSol exclusive). The PRO Series III is the only steam generator in the world that uses ThermaSol's patented Smart Steam system. Conventional steam generators — from every brand — work by cycling on and off to maintain temperature. This produces temperature swings throughout the session: the steam surges when the generator fires, then drops off as it waits to cycle back on. Smart Steam eliminates this by continuously modulating generator output to deliver constant steam at a constant rate. The result is a measurably smoother, more consistent steam experience from the first minute to the last. This is not a marketing claim — it is a patented, verifiable engineering difference that no other brand can replicate.
FastStart technology. The PRO Series III reaches steam temperature in seconds, not the several minutes required by conventional generators. For a homeowner who steps into the shower and expects the experience to begin immediately, this is a meaningful quality-of-life improvement over competing systems.
PowerFlush automated cleaning system (ThermaSol exclusive). Mineral scale buildup inside the generator tank is the leading cause of steam generator failure across all brands. The PRO Series III includes ThermaSol's PowerFlush system — an automated inner-tank cleaning mechanism that manages mineral buildup without any manual intervention required. This is particularly important in hard water areas and meaningfully extends generator life compared to units without automated cleaning. For more on why hard water management matters, see our hard water and steam generator protection guide.
Beyond these three core technologies, every PRO Series III is built with an industrial-grade stainless steel tank, can be installed up to 50 feet from the shower space, uses ThermaSol's CAN Bus digital communication system to connect all ThermaSol components intelligently, and is manufactured in the USA. ThermaSol joined the Harvia family of wellness brands in 2024 — Harvia, founded in Finland in 1950, is the world's leading sauna and spa company operating in over 80 countries — a partnership that strengthens ThermaSol's position in the broader wellness space, including saunas, cold plunges, and hot soaks.
The warranty
The PRO Series III is backed by ThermaSol's no-questions-asked lifetime warranty — the only warranty of its kind in the residential steam generator category. Coverage is 2 years parts and labor in-home, with lifetime factory coverage beyond that. No other brand offers a comparable lifetime warranty on a residential steam generator.
PRO Series III model lineup
The PRO Series III covers steam rooms from 84 to 1,200 cubic feet across seven models. The model number tells you the maximum room volume in cubic feet at a standard 8 ft ceiling height.
| Model | Max room (cu ft) | Output (kW) | Voltage |
|---|---|---|---|
| PROIII-84 | 84 | 6 kW | 240V |
| PROIII-140 | 140 | 8 kW | 240V |
| PROIII-240 | 240 | 10 kW | 240V |
| PROIII-395 | 395 | 11 kW | 240V |
| PROIII-575 | 575 | 15 kW | 240V |
| PROIII-750 | 750 | 20 kW | 240V |
| PROIII-1200 | 1,200 | 24 kW | 240V |
All seven models run on 240V single-phase power and require a dedicated circuit. The generator installs in a finished, climate-controlled space — a closet, cabinet, or adjacent room — up to 50 feet from the steamhead.
How to size the right model
ThermaSol's sizing method is straightforward and notably different from Mr. Steam and Amerec in one important way — wall material does not affect the sizing calculation. Whether your shower is tiled, marble, granite, or glass, you size the same way.
Step 1: Calculate your shower's cubic footage — length × width × height.
Step 2: Adjust for ceiling height:
— At 8 ft ceiling: use the cubic footage as calculated
— At 9 ft ceiling: size up one model
— At 10 ft ceiling: size up two models, or contact us to confirm
For example: a 4×5×8 ft shower is 160 cubic feet — the PROIII-240 (covers up to 240 cu ft) is the correct model with comfortable headroom. The same shower at 9 ft ceiling height would size up to the PROIII-395.
Not sure which model is right for your space? Use our steam generator sizing tool or contact our team and we will size it for you.
Which model for which project
PROIII-84 — compact tile steam showers at standard ceiling height up to 84 cubic feet. A typical 3×4 or 4×4 ft enclosure at 8 ft.
PROIII-140 — the most common size for a standard residential steam shower. Generous enclosures up to 140 cubic feet and the sweet spot for most master bath installations at standard ceiling height.
PROIII-240 — larger luxury master bath steam showers up to 240 cubic feet, or standard enclosures with a 9 ft ceiling that require sizing up from the PROIII-140.
PROIII-395 — generous residential steam rooms and high-ceiling master baths up to 395 cubic feet. A popular choice for high-end custom builds with natural stone and dramatic ceiling heights.
PROIII-575 — large luxury steam rooms up to 575 cubic feet. Suited for dedicated steam room spaces separate from the main shower.
PROIII-750 — very large residential or boutique commercial steam rooms up to 750 cubic feet. For significant dedicated wellness spaces in high-end residential or hospitality applications.
PROIII-1200 — ThermaSol's largest single PRO Series III unit, covering rooms up to 1,200 cubic feet. Purpose-built for commercial steam rooms, hotel spas, and large-scale residential wellness installations.
The ThermaSol control ecosystem
The PRO Series III connects to ThermaSol's full control lineup via the CAN Bus digital communication system. All controls are sold separately and paired with the generator. Three options are available:
ThermaTouch2 — ThermaSol's flagship touchscreen control, available in 7", 10", and 15" screen sizes. The 15" ThermaTouch2 is the largest in-shower touchscreen control available from any brand. Controls steam, water temperature, lighting, and audio from a single interface, with access to streaming apps including Netflix, Apple Music, Spotify, and more. Amazon Alexa integration, built-in Wi-Fi, customizable user profiles, and full chromatherapy and aromatherapy control. Compatible with ThermaSol's Digital Shower Valve for a fully integrated multi-sensory experience. Available in 15 finishes.
SignaTouch 5 — a 5" touchscreen control that manages steam, shower outlets, audio, chromatherapy, and lighting. Includes two customizable user profiles and integrated Bluetooth. Available wall-mounted or recessed, in vertical or horizontal orientation, in 15 finishes.
MicroTouch — ThermaSol's entry-level control. Simple, intuitive steam and temperature management in a compact round or square format. Available wall-mounted or recessed, in 15 finishes. Also available with an integrated SteamVection steamhead.
Browse the full ThermaSol controls collection or see our ThermaSol smart controls guide for a complete breakdown.
PRO Series III vs. Mr. Steam and Amerec
| ThermaSol PRO Series III | Mr. Steam MS Series | Amerec AK Series | |
|---|---|---|---|
| Steam technology | Smart Steam — continuous modulation (patented) | Standard on/off cycling | Sequential Temperature Control — modulated |
| Automated cleaning | PowerFlush — built in | AutoFlush — optional add-on | ADK Auto Drain — included in select packages |
| Max single unit | 1,200 cu ft | ~900 cu ft (MS225E) | 550 cu ft (AK14), gangable to 1,500 |
| Max install distance | 50 ft from steamhead | 60 ft from steamhead | 25 ft from steamhead |
| Wall material sizing | No adjustment — cubic footage only | 1.75× multiplier for natural stone | 1.75× multiplier for natural stone |
| Warranty | Lifetime (no questions asked) | Limited lifetime | 1 year parts, 1 year labor |
| Manufactured | USA | USA | USA |
| Smart home | Amazon Alexa via ThermaTouch2 | Amazon Alexa via iSteamX | Google Home + Amazon Alexa via K2 |
Not sure which brand is right for your project? The PRO Series III is the premium choice when consistent steam quality, automated maintenance, and a fully integrated control system are the priority. If smart home voice control via both Google Home and Alexa is the deciding factor, the Amerec K2 control supports both. If breadth of options and the widest distribution network are the priority, Mr. Steam covers the broadest range. Contact us and we will help you decide.
Frequently asked questions
Does ThermaSol adjust generator sizing for natural stone walls?
No — ThermaSol's sizing formula is based on cubic footage only. Wall material does not affect which PRO Series III model you need. This is a meaningful difference from Mr. Steam and Amerec, which both apply a 1.75× multiplier to the base cubic footage for natural stone enclosures.
How far can the generator be from the shower?
Up to 50 feet. The generator must be installed in a finished, climate-controlled space — a closet, cabinet, vanity, or adjacent room. It must not be installed in an unfinished or unheated space.
What electrical circuit is required?
All PRO Series III models require a dedicated 240V single-phase circuit. Circuit sizing depends on the model — contact us and we will provide the electrical requirements for your specific model.
What is the PRO Series III warranty?
ThermaSol's no-questions-asked lifetime warranty covers the PRO Series III: 2 years parts and labor in-home, lifetime coverage at the factory. This is the most comprehensive warranty available on any residential steam generator.
Can the PRO Series III be used for commercial applications?
The PROIII-1200 covers commercial-scale steam rooms up to 1,200 cubic feet in a single unit. For larger commercial applications, ThermaSol's PowerPak Series III — available at 18kW and 24kW in three-phase configurations — is the correct choice. Browse the ThermaSol commercial steam collection for those options.
Is the PRO Series III compatible with any control?
The PRO Series III is designed to work with ThermaSol's full control lineup — ThermaTouch2, SignaTouch 5, and MicroTouch — all connected via the CAN Bus system. ThermaSol controls are sold separately. The generator is not compatible with Mr. Steam or Amerec controls.
Why order from TheSteamStore.com?
- Authorized ThermaSol dealer — we carry the complete PRO Series III lineup and all ThermaSol controls with full warranty coverage
- Sizing support — not sure which model you need? Contact our team and we will size the right generator for your space at no charge
- Free shipping — on all orders over $199 within the contiguous United States
- Expert support — call us at 877-881-5501 Monday through Friday
Browse the complete ThermaSol PRO Series III collection at TheSteamStore.com, or contact us to get a sizing recommendation for your project.