If you're running a gym, wellness centre, day spa, hotel, or apartment complex with a communal sauna, the heater specification matters more than most people realise. A residential heater is designed for a few sessions a week. A commercial sauna might run six to sixteen hours a day, every day. That's a different ask entirely.
This guide covers what to look for in a commercial sauna heater, which models we stock and can order, and how to choose the right controller for your facility.
What Makes a Commercial Sauna Heater Different?
Three things matter most: durability, stone capacity and kW output.
A home sauna might run three or four sessions a week. A gym sauna or public sauna can run six to eight hours a day, every day. That repeated thermal cycling puts significant stress on the heating elements, which are the most common failure point in lower-specification heaters.
Commercial-grade heaters are built with heavier, larger-diameter elements that distribute heat across a greater surface area. That reduces the risk of overheating and extends the replacement cycle significantly. For a facility manager, that means fewer call-outs and lower long-term maintenance costs.
Stone capacity is the other key factor. A large stone mass holds heat through frequent door openings and recovers temperature faster between groups. It also produces better löyly, the soft, sustained steam that defines a quality sauna experience. In a commercial setting, that consistency matters.
Narvi Ultra - Small Gym Sauna, Wellness Studio, Private Spa
The Narvi Ultra is what we recommend for small to medium commercial applications. We have this in stock and ready to ship from Auckland.
Available in two outputs:
Ultra 10.5 kW - suits rooms of 9–15m³. A small gym sauna, boutique wellness studio, or private spa treatment room.
Ultra 15 kW - suits rooms of 14–20m³. A medium-sized gym sauna, wellness centre, or small hotel sauna facility.
Both models carry 50kg of stone capacity and come with the Narvi Flow Wifi controller as standard. The heating elements have a large diameter of 8.5mm, significantly larger than most residential heaters, which extends element life and reduces overheating risk in a continuous-use environment. Stainless steel casing. Floor-standing with short safety clearances.
Narvi Ultra Big - Large Gym Sauna, Hotel, Public Sauna
For larger commercial spaces, hotel saunas, day spas, public saunas, large gym facilities, and communal apartment saunas, the Ultra Big is the right specification.
Available from 18 kW to 30 kW, the Ultra Big suits rooms from 18m³ upward. Stone capacity goes up to 120kg. In a busy public sauna or large gym facility, that stone mass is what keeps löyly quality consistent across a full operating day, even with people cycling in and out regularly.
The Ultra Big requires an external power unit and controller in the anteroom. A full commercial control setup, designed to safely manage the high current draw of an 18–30 kW heater.
Available to order. Get in touch for pricing and lead times.
Narvi Peak - Spa, Wellness Retreat, Premium Apartment Sauna
The Narvi Peak suits commercial environments where the heater is also part of the design. Spas, wellness retreats, high-end hotel sauna facilities, and premium apartment developments where the sauna is a feature, not just a utility.
Where the Ultra is a straightforward floor-standing unit, the Peak has a distinctive round, self-standing form that works as a visual centrepiece in the space. Built to the same commercial durability standard and carrying the stone capacity a busy commercial sauna needs.
Available to order with the right controller for your application. Get in touch to discuss.
Controller Options
Getting the controller right is as important as getting the heater right. In a commercial setting you need scheduling, automation, and the ability to lock down settings so members or guests can't change the configuration.
Narvi Flow Wifi - included with the Ultra. App-controlled with remote on/off, delay start, temperature and timer setting. On/Off Mode is what most commercial operators use, the user simply turns the sauna on and it runs to preconfigured settings. No access to temperature or time controls. Easy Mode allows users to adjust operating time and temperature but not system defaults. A door switch is included for safe remote operation. Works well for gyms, wellness studios, and short-term rental properties.
Narvi C-2003 + F-2003 - a dedicated commercial controller setup suited to facilities with fixed operating schedules. The C-2003 is the power unit and the F-2003 is the control panel, giving you weekly scheduling, precise temperature control, and a straightforward interface for facility staff. Required for the Ultra Big range and Peak. Can be ordered for the Ultra as an alternative to the Flow Wifi where app-based control isn't preferred.
Narvi Logi - the professional-grade control system for large facilities and building automation integration. Designed specifically for heavy commercial use. Controls the sauna via the facility's local network, so a hotel reception or swimming hall control room can manage the sauna remotely without needing to be near the unit. Features customised access levels for different user groups (user and admin), anomaly alerts, two operating periods per day, a maintenance program, and a resistor group rotation function that extends element life in high-use environments. Connects via Modbus TCP, making it compatible with building automation systems. Optional add-ons include steam control and lighting management.
If you're not sure which controller suits your setup, get in touch. The right choice depends on your operating hours, who has access to the sauna, and whether you need building automation integration.
Sizing a Commercial Sauna Heater
The same calculation applies as for residential: 1 kW per cubic metre of room volume, plus 1.5m³ added for each square metre of non-insulated surface, glass walls, tiled surfaces, concrete.
Commercial saunas often have more glass and tile than a home sauna, so the adjustment for non-insulated surfaces matters more in a commercial spec. A large glass wall or a tiled floor adds real kW to your requirement.
Our sauna heater sizing calculator works for commercial rooms. Run your dimensions through it as a starting point. For larger or more complex spaces, get in touch and we'll work through the sizing with you before you order.
Replacing an Existing Commercial Sauna Heater
If you're replacing a heater in an existing commercial sauna, a few things are worth checking before you order.
Electrical supply - the Ultra 15 kW requires 400V 3-phase with a 3x25A fuse. The Ultra Big range requires more still. Confirm your building's electrical capacity with your electrician before you select a heater and controller.
Room volume - take internal measurements and run the sizing calculation. If the previous heater was undersized, this is the opportunity to fix it.
Stones - if you're replacing the heater, replace the stones at the same time. Don't load old stones into a new heater.
Controller - if you're changing heater models, confirm the existing controller is compatible or factor in a new one.
Final Thoughts
For any commercial sauna in New Zealand, whether that's a gym, spa, hotel, wellness centre, public sauna, or apartment complex, the Narvi Ultra range is what we stock and recommend. Finnish-made, engineered for continuous use, and backed by over 80 years of sauna heater manufacturing.
The Ultra is in stock and ready to ship from Auckland. The Ultra Big and Peak are available to order.
For commercial enquiries, sizing advice, controller selection, freight, or installation guidance, get in touch directly. Commercial projects are worth a conversation before you order.
