HUUM Hive Sauna Heaters

The Hive: HUUM's Biggest Heater

The Hive is the heater you buy when nothing smaller will do the job. It's a freestanding cylindrical cage that stands on the sauna floor, and it carries 595 lbs of stone — the heaviest stone load HUUM makes, and one of the largest in the home and light-commercial category. That mass is the whole point. When you have that much stone holding heat, the room recovers almost instantly after a water pour, and the steam stays soft and humid instead of sharp and dry.

The cage measures 29.5" tall, 22" wide, and 22" deep, and it sits on the floor rather than mounting to a wall — there's simply too much weight here for a bracket. Like every HUUM electric heater, the elements are buried deep in the stone column, so what radiates into the room is heat off thermal mass, not heat blowing past exposed coils. If you've been comparing options across the HUUM electric heater range, the Hive is the top of the lineup — the one built for 500+ cubic feet.

How to Choose Your Wattage

Match kW to room volume

The Hive covers a wide span: roughly 424 to 1,236 cubic feet across the three wattages. The 12kW handles large home saunas and smaller outdoor cabins. The 15kW steps up for big rooms — think 6–8 person builds or a generously sized outdoor cabin. The 18kW is built for the largest rooms, high-ceiling builds, and light-commercial spaces like gym and spa saunas that get used hard all day. When you're between two sizes, size up. Glass doors, tile, stone benches, and cold exterior walls all pull a room's effective heat demand higher, and an underpowered Hive in a big room is a Hive that never quite hits temperature.

Plan the electrical before you order

The Hive is a serious electrical load and needs real planning. At 240V, the 12kW pulls 50 amps and lands on a 60A breaker. The 15kW pulls 62.5 amps and needs an 80A breaker. The 18kW pulls 75 amps and needs a 90A breaker on heavy-gauge wire. Many large installs run these on three-phase where it's available, which changes the amperage per leg — your electrician will spec that based on your panel. Every Hive needs its own dedicated circuit, and a heater this size is not a DIY hookup. Our guide to sauna electrical rough-in covers what to confirm before your licensed electrician runs the circuit. Always consult a licensed electrician — requirements vary by local code.

The controller, and the Extension Box you may need

The Hive will not run without a HUUM UKU controller, which is sold separately. That's deliberate — HUUM decouples the controller from the heater so you pick the interface that fits your space. There's an important catch on the Hive: because the 15kW and 18kW exceed 12kW, both require the UKU Extension Box in addition to the UKU controller. The Extension Box handles the higher current the controller can't switch on its own. The 12kW does not need it. Budget for the box if you're going with the 15kW or 18kW.

The UKU Controller (Required, Sold Separately)

Browse the full lineup in our UKU controller collection, but here's the short version. UKU Local is a wired wall panel with no WiFi — for buyers who don't want their sauna on the internet. UKU WiFi adds the HUUM mobile app, so you can preheat from your phone on the drive in and schedule recurring sessions, which matters a lot for a commercial sauna on a daily heat-up routine. UKU Glass and UKU Mirror are the WiFi version dressed in premium glass or mirror finishes. For a high-use Hive install, the WiFi-enabled UKU models earn their keep through scheduling alone — you can see the rest of our WiFi-controllable heaters if app control is a priority across your build.

Stones, Steam, and What That 595 lbs Buys You

The Hive's defining feature is its stone mass. At 595 lbs of olivine diabase, it holds far more thermal energy than a wall-mount heater, and that translates directly into how the room feels. Throw water on a fully loaded Hive and the room fills with humid löyly without the temperature crashing — the stones have so much reserve heat that recovery between pours is near-instant. This is the difference between a heater that produces a brief hiss and a heater that sustains a traditional Finnish steam session for an hour.

Use 2"–4" rounded olivine stones and fill the cage fully, packing around but never wedging against the elements so airflow stays even. You can source the right stone from our sauna rocks collection. A Hive run with the basket half-empty won't deliver the steam it's engineered for, and it puts unnecessary stress on the elements — fill it to spec.

Hive vs. the Rest of the HUUM Lineup

The Hive is the largest HUUM electric, so the comparison is really about whether your room actually needs this much heater. The HUUM Hive Mini is the cylindrical look of the Hive scaled down to 330 lbs of stone and 6–10.5kW — the right call for mid-size 2–5 person rooms where a full Hive would be overkill. The HUUM Cliff is the sculptural freestanding pillar with 165–202 lbs of stone, strong löyly for 4–6 person cabins without going to the Hive's weight. The HUUM Drop is the wall-mounted teardrop at 121 lbs, for typical home saunas where floor space is tight. And the HUUM Steel is the budget entry point in a rectangular shell.

Choose the Hive when your room is genuinely large — roughly 425 cu ft and up — or when it's a commercial or light-commercial space that needs maximum stone mass and the ability to recover through constant use. If your room is smaller than that, the Hive Mini or Cliff will heat it better and cost less to run, because you're not paying to keep 595 lbs of stone hot in a room that doesn't need it.

Safety, Accessories, and What to Order Alongside

The Hive reaches a 230°F surface — the highest max temp in the category — and at this size it commands a lot of floor presence, so a guard rail keeping benches and bodies clear of the cage isn't optional in a room where seating sits close. Stones are mandatory before the heater can be powered on. If you're sourcing parts à la carte, plan on heater + UKU controller + stones for the 12kW, and heater + UKU controller + UKU Extension Box + stones for the 15kW and 18kW. If you'd rather not piece it together, our HUUM electric heater packages bundle the heater, your choice of UKU controller, and stones at a package price. The Hive also sits in our broader 12kW heater collection if you're cross-shopping that wattage across brands.

HUUM's warranty runs 3 years on the heater body and UKU controller for residential use, and it's valid only through authorized dealers like Topture. Grey-market Hives from Amazon and eBay resellers frequently aren't covered by HUUM even when the product looks identical — confirm the dealer before you order. We're an authorized HUUM dealer, ship every Hive free, and our team is available if you hit a question during install.