HUUM Sauna Heaters: DROP, CLIFF, HIVE and CORE Compared

HUUM builds every electric heater around the same two things: an unusually large mass of exposed stone, and one family of controls called the UKU. DROP hangs on the wall for small rooms. CLIFF and STEEL are slim floor pillars. CORE is a body you clad yourself. HIVE is the big one. Match kW to room volume, then pick the shape.

• Small room, no floor to spare. DROP 4, wall mounted, 106 to 247 cu ft.
• Tight room, floor available. CLIFF or STEEL. Slim pillars with small safety distances.
• You want the heater to disappear. CORE. You finish it in tile, stone, glass or wood, and you can recess it into a bench.
• Big room or commercial. HIVE, up to 18 kW and 528 lb of stone.

In this article

Which HUUM heater should you buy?

HUUM rates its heaters by room volume in cubic feet. Measure width times depth times height in feet. Then add for anything that soaks up heat instead of reflecting it. Glass, tile, concrete, stone and exposed log all make a room act bigger than it measures. Our sizing guide and the size calculator handle that for you. Size to the larger number, because a heater that's too small never gets the room right.

Browse the full HUUM range, or the wider electric sauna heater collection if you're still comparing brands.

Why do HUUM heaters hold so much stone?

Take the DROP 4. It's a 4.5 kW heater, the smallest step in the range, and it carries 122 lb of stone. That's more than the 77 lb minimum a Narvi Kuru wood stove needs. The CLIFF 6 carries 165 lb at 6 kW. For comparison, a Harvia KIP60W at the same 6 kW holds 44 lb.

Kilowatts heat the air in the room. The stone stores that heat and releases it as steam when you pour. A small load of stone heats up fast, then fades after two or three ladlefuls and needs time to recover. A big load takes longer to heat up. Once it gets there, it keeps making soft, even steam for a whole session, and that's what most people mean when they say a sauna "feels" better. HUUM also sits the stones right against the elements rather than behind a shield, so the heat goes into the rock instead of only into the air.

CORE is the exception. It holds 66 lb, the smallest load HUUM offers, because the body is a slim 12.2 in column meant to be clad or buried in a bench. You buy CORE for how it looks in the room, not for the steam.

Which stones does my HUUM take?

This is the easiest thing to get wrong when you order. HUUM uses two stone grades across the range, and the wrong one won't stack properly in the basket. The rule goes by series, not by kW.

• CLIFF and STEEL take Extra Small, 3 to 5 cm. Both are narrow pillars, and the smaller stone packs correctly around the internal air duct.
• DROP, HIVE, HIVE Mini, CORE and the HUUM wood stoves take Small, 5 to 10 cm.
• Rounded olivine, never split face. HUUM specifies rounded stone rather than the split-face rock other brands use. It suits the open HUUM basket and gives a milder steam.

Both grades ship in 33 lb boxes at $80. To work out how many you need, divide the heater's stone capacity by the box weight and round up. A DROP 4 needs four boxes for its 122 lb, a CLIFF 6 needs five for 165 lb, a STEEL 6 needs ten for 331 lb, and a HIVE 12 needs sixteen for 528 lb. Stones are never included with the heater. See all sauna stones, and our sauna rocks guide for the full method.

Once they're in, looking after them is simple, and it matters more on a HUUM than on a small-basket heater. Stack them loosely by hand so air moves freely between them, never tightly packed and never empty. Re-stack the whole load once a year. Pull out any stone that has cracked or started to crumble instead of waiting for it to break down further.

Why does every HUUM need a UKU control?

Every HUUM electric heater ships with no controls on the body at all. There's no dial, no timer, nothing. A UKU control isn't an upgrade, it's the part that makes the heater run, and it mounts outside the hot room. Budget for it from the start, because it's a big share of what you'll pay.

There are two of them, and the only difference is whether you want your phone involved.

• UKU Wi-Fi, from $1,324. The HUUM app, eight languages, unlimited users. Start the sauna from the house, from work, from the car.
• UKU Local, from $1,062. Panel only, no app and no network. It still has a delayed start of up to 48 hours, and that covers most of what people actually use the app for.

Both ship with a 16.4 ft temperature sensor, a 9.84 ft panel cable and a 16.4 ft door sensor, and both work with every HUUM electric heater. Here's the one limit to watch out for. A UKU can switch 11 kW on its own. Above that you also need the UKU Extension Box at $773, which in practice means the HIVE 12, 15 and 18. Everything else in the range stays under that limit, including the CLIFF 11 and STEEL 11 at 10.5 kW and the HIVE Mini 11 at 10.6 kW. Our sauna control panel guide explains what a control does beyond switching.

What about HUUM wood stoves?

HUUM makes two wood-fired families, and neither one needs electricity. That's the whole point for an off-grid cabin. HIVE Wood 13 at $2,150 covers 212 to 459 cu ft with 198 lb of stone; HIVE Wood 17 at $2,350 goes to 565 cu ft with 286 lb. The HIVE Flow models, from $2,898, are the lower-output, longer-burn design. LS variants of both add a firebox extension so you can feed the fire from outside the hot room.

They carry CE marks. Even so, a solid-fuel appliance needs a permit and an inspection in most US areas. Your insurer will normally want that sign-off too, so plan the chimney early. Our wood burning sauna stove guide covers flues, clearances and floor protection, and you can see the wider range in wood burning sauna stoves.

Frequently asked questions

Does a HUUM sauna heater come with a control?

No, and it can't run without one. Every HUUM electric heater ships with no controls on the body. You add a UKU Wi-Fi or a UKU Local. It mounts outside the hot room, so you can bring the sauna up to temperature before you walk in.

What stones does my HUUM heater take?

Rounded olivine, in one of two sizes depending on the series. CLIFF and STEEL take Extra Small, 3 to 5 cm. DROP, HIVE, HIVE Mini, CORE and the HUUM wood stoves take Small, 5 to 10 cm. Split-face stone isn't the right shape for a HUUM basket.

Do HUUM heaters include sauna stones?

No. Stones are always sold separately and the heater must never be run empty. Divide the stone capacity by the 33 lb of stone in a box and round up: a DROP 4 needs four boxes, a CLIFF 6 needs five.

Do I need the UKU Extension Box?

Only above 11 kW, which in the current range means the HIVE 12, HIVE 15 and HIVE 18. A UKU on its own can't switch those loads. Everything at 10.6 kW and below runs on the control alone.

Which HUUM heater suits a small sauna?

If the floor is tight, the DROP 4 at 4.5 kW hangs on the wall and covers 106 to 247 cu ft. If you have the floor space, the CLIFF Mini 4 or STEEL Mini 4 at 3.5 kW cover 123 to 212 cu ft with unusually small safety distances.

Can a HUUM heater plug into a normal outlet?

No. Every HUUM electric heater is hardwired on a dedicated 240V single-phase circuit. A licensed electrician sizes the breaker and conductors from the nameplate and the installation manual under the current NFPA 70. Our guide to sauna heater installation covers what that circuit costs. You'll find full specs for each model on HUUM's own site and on every product page here.