Description
The Hot Box is a commercial-scale sauna that arrives finished. Hot Blue build it off-site in Liverpool and deliver it fully assembled, which sidesteps the part of a commercial sauna project that usually causes the delay and the argument: constructing a heat-rated timber room inside a building that wasn’t designed for one.
It seats up to eight on three tiers of thermo-aspen, behind roughly 4m² of glazing. The heater is a HUUM HIVE at 18kW — a genuinely commercial output, not a domestic unit working hard — and it’s controlled over Wi-Fi from a phone, which matters more than it sounds if you’re opening a gym at 6am and want the room already at temperature.
Who it’s for
Hot Blue position the Hot Box for home, hospitality and commercial use, but the specification points squarely at the commercial end: eight-person capacity and an 18kW heater are more than a household needs. It makes most sense for a site that wants a sauna without a construction project — a gym or leisure club, a hotel or spa, a campsite or holiday park, a padel or racket venue, a recovery studio, or an operator testing a location before committing to a permanent build.
Because it’s delivered as a finished unit rather than fitted in situ, it also suits leased premises where you can’t justify permanent alterations. It sits on heavy-duty commercial wheels, so once the hiab has set it down it can be rolled into position rather than craned into an exact spot — and moved again later if the site changes, or fixed permanently if it doesn’t.
The electrical supply is the thing to check first
This is where commercial sauna projects most often stall, and it’s worth understanding before you enquire.
HUUM’s own specification for the HIVE 18 lists a 3/N~400V three-phase supply, a 32A fuse and a 5 × 6mm² cable. That is not a domestic arrangement. An 18kW load on a single-phase 230V supply would draw roughly 78A, which is why three-phase isn’t a preference here — it’s a requirement of the heater.
Most industrial and commercial premises already have three phase. Many hotels, converted buildings, rural campsites and leased retail units do not, and the cost of bringing in a new supply can run to thousands and take months. If you’re considering this unit, confirm what’s at your meter before anything else.
HUUM also rate the HIVE 18 for rooms of 18–28m² of volume and specify 250kg of sauna stones, which gives a reasonable sense of the cabin’s internal scale even though Hot Blue don’t publish exterior dimensions.
Specification
| Item | Detail |
|---|---|
| Capacity | Up to 8 people, three-tier benching |
| Heater | HUUM HIVE, 18kW electric (HUUM HIVE WOOD wood-fired available as an option) |
| Electrical supply | 400V three-phase, 32A — per HUUM’s HIVE 18 specification |
| Timber | Thermo-aspen floors, walls, ceiling and benches |
| Glazing | Approximately 4m² |
| Lighting | Fully dimmable |
| Control | Wi-Fi, operated by smartphone |
| Mobility | Heavy-duty commercial wheels — rolled into position after delivery, repositioned later, or fixed permanently |
| Delivery | Manufactured off-site, delivered fully assembled by hiab; nationwide UK delivery and turnkey installation available |
Options
- Elite Ice Bath — for contrast therapy alongside the sauna
- HUUM HIVE WOOD — wood-fired heater instead of electric, which removes the three-phase requirement but adds fuel handling, a flue and staff time
- Thermo-aspen shower
- Exterior cladding
- Bluetooth audio
What Hot Blue don’t publish yet
We list what we can verify. As of September 2026, Hot Blue don’t publish the following, and they’re the questions we’d want answered before signing anything:
- Price. There’s no figure on their site or in any public listing. Pricing is indicative and by enquiry.
- External dimensions and weight. Critical for the hiab lift, for getting it through a gate or side return, and for checking a floor or ground loading.
- Warranty terms and lead time.
Hot Blue Ltd is based at 95–113 Great Howard Street, Liverpool, and was incorporated in September 2025 — a young company, which is worth knowing when you’re weighing a significant capital purchase. Viewings are by appointment. They offer a brochure with specifications, upgrade options and indicative pricing on request.
Before you commit
Three-phase power is the first check. After that, the ones that catch people out on commercial installations are ventilation, supervision and insurance — a sauna in a members’ venue is a different risk conversation from one in a garden. Our guide to commercial saunas covers the specification and compliance side, and if you’re buying a unit to rent out or run as a business, mobile saunas is the more relevant starting point.
SaunaCentral doesn’t sell saunas. Hot Blue is a commercial partner of ours — see our affiliate disclosure — and we’ve still said plainly above what we don’t know about this unit, because a partnership doesn’t change what the specification sheet does and doesn’t contain. If you’d like a quote or the brochure, use the enquiry form below and we’ll pass it on — or compare other UK sauna builders, several of whom build commercial and mobile units to order.
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