HUUM Sauna Heaters

HUUM builds its sauna heaters in Estonia around one idea: put the stone in the open, in contact with the elements, instead of hiding it behind a steel skin. That is what gives these rooms their soft, wet heat, and it is why the DROP won a Red Dot design award. Five electric families from 4 to 18 kW, one UKU control that runs all of them from the wall or your phone, and olivine diabase stone by the box.

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The HUUM story

HUUM Sauna Heaters: Estonian Design, Built Around the Stone

HUUM is an Estonian manufacturer founded by Siim Nellis, a third generation sauna stove producer who set out to combine a sauna heater with modern design and modern control. The company works out of Tartu, in southern Estonia.

The DROP is the heater that made the name. It was developed in 2011 with the Estonian Academy of Arts, reached production in 2012, and won the Red Dot product design award in 2015. Its shape is not styling for its own sake: rounding the cage and cutting the metal surface lets the heater hold more stone for its size, which is where a sauna gets its soft heat and its steam.

Every HUUM electric heater follows the same idea. The stone sits in the open, in direct contact with the elements, rather than hidden behind a steel skin. You see the stone, you throw water onto the stone, and the room settles instead of swinging. The other half of the brand is the UKU control, which runs the heater from outside the room or from your phone.

A HUUM DROP sauna heater on the wall of a sauna while water is ladled onto its stones
EstoniaDesigned and Built
4 to 18kWOutput Range Stocked
106 to 989Cubic Feet Covered
3 YearsPrivate Use Warranty

The range

The HUUM Lineup: Five Electric Heater Families

Every HUUM electric heater takes a separate control and its own quantity of stone. What separates the families is where the heater sits, how much stone it carries, and how it looks doing it.

DROP

The Red Dot winner, and the only HUUM heater light enough to ship by parcel. It hangs on the wall as an open cradle, in four sizes from 4.5 to 9 kW, all carrying the same 121.3 lb of stone. For rooms from 106 to 460 cubic feet. See the DROP 4, DROP 6, DROP 7 and DROP 9.

CLIFF and CLIFF Mini

The slimmest heater HUUM makes: a 10.6 inch square column with removable ribs, so the stone packs tightly against the elements. CLIFF 6, 9 and 11 stand on the floor and hold 165 lb of stone. CLIFF Mini 4 is 6.3 inches deep and hangs on a wall bracket, for a room too small for anything else. See the CLIFF Mini 4, CLIFF 6, CLIFF 9 and CLIFF 11.

STEEL and STEEL Mini

A 12.6 inch square body, a little wider than the CLIFF, carrying twice the stone: 330 lb on STEEL 6, 9 and 11. STEEL Mini 4 hangs on a wall bracket like the CLIFF Mini. For rooms from 106 to 566 cubic feet. See the STEEL Mini 4, STEEL 6, STEEL 9 and STEEL 11.

HIVE and HIVE Mini

The round basket, and the heaviest stone load HUUM makes: 330 lb on the Mini and 528 lb on the full size. HIVE 12, 15 and 18 are the models for a large or commercial room, and they run through the UKU extension box. See the HIVE Mini 6, Mini 9, Mini 11, HIVE 12, HIVE 15 and HIVE 18.

CORE

A square heater designed to be finished in the same timber as your room, or left black. Alder, aspen and thermo-aspen panels, with a black or stainless trim ring, in 6.5, 9 and 10.5 kW: the CORE 6, CORE 9 and CORE 11.

Wood stoves

HUUM builds two wood burning ranges for a sauna with no electrical supply, or an owner who wants the fire. The HIVE Wood holds its stone in a cage around the firebox; the HIVE Flow adds a glazed door and puts more of the heat into the room. Both come in a through the wall version that is fed from the next room, the HIVE Wood 17 LS and the HIVE Flow LS. They hold European certification and no North American listing, and the chimney has to satisfy your building department, so talk to us before you plan one. Every stove page sets out what that means.

Side by side

The Five Families Compared: Mounting, Output, Room and Stone

Family Mounting Output Room at 240 V Stone it holds Boxes Stone size
DROP 4 to 9 Wall 4.5 to 9 kW 106 to 460 cu. ft. about 121.3 lb 4 2 to 4 in
CLIFF Mini 4 Wall bracket 4 kW 106 to 177 cu. ft. about 132 lb 4 1.2 to 2 in
CLIFF 6 to 11 Floor 6 to 11 kW 177 to 566 cu. ft. about 165 lb 5 1.2 to 2 in
STEEL Mini 4 Wall bracket 4 kW 106 to 177 cu. ft. about 132 lb 4 1.2 to 2 in
STEEL 6 to 11 Floor 6 to 11 kW 177 to 566 cu. ft. about 330 lb 10 1.2 to 2 in
HIVE Mini 6 to 11 Floor 6 to 10.6 kW 177 to 566 cu. ft. 331 lb 10 2 to 4 in
HIVE 12 to 18 Floor 12 to 18 kW 424 to 989 cu. ft. 16 boxes 16 2 to 4 in
CORE 6 to 11 Floor 6.5 to 10.5 kW 177 to 566 cu. ft. about 88.2 lb 3 2 to 4 in

Every figure here is HUUM's own, from the current US manuals. On a 208 volt supply the same heater is rated for a smaller room. The HIVE 12, 15 and 18 are the only models that need two supply circuits and the UKU extension box.

Sizing

What Size HUUM Sauna Heater Do I Need?

Sauna heaters are sized on room volume, not floor area, and HUUM publishes a range for every model. Get this right and the room reaches temperature in about an hour and holds it. Get it wrong in either direction and you either wait, or the heater satisfies its thermostat before the stone is charged and the steam comes thin.

Measure in cubic feet

Length times width times height, in feet. A 7 by 6 room with a 7 foot ceiling is 294 cubic feet, which is a 6 kW job.

Count the cold surfaces

HUUM's manuals say to add 3.3 cubic feet for every square foot of uninsulated brick, tile or glass wall. We count a full glass door the same way, and it is often enough to move you up a model. The result is your adjusted cubic feet.

Check your voltage

Every figure below is for 240 volts. On a 208 volt supply the same heater makes less power and covers a smaller room, so size from the 208 volt row instead.

Mind the ceiling

HUUM sets a minimum room height per family: 75 inches for the DROP, 77 for the HIVE, 80 for the CORE and 86.6 for the CLIFF and STEEL. It also asks for 44 to 51 inches between the top bench and the ceiling.

Swipe the table sideways on a phone.

Adjusted room volume Output Circuit at 240 V HUUM models
106 to 177 cu. ft. 4 kW 20 A CLIFF Mini 4, STEEL Mini 4
106 to 248 cu. ft. 4.5 kW 30 A DROP 4
177 to 318 cu. ft. 6 to 6.5 kW 30 A DROP 6, CLIFF 6, STEEL 6, HIVE Mini 6, CORE 6
248 to 389 cu. ft. 7.5 kW 40 A DROP 7
283 to 460 cu. ft. 9 kW 50 A DROP 9, CLIFF 9, STEEL 9, HIVE Mini 9, CORE 9
354 to 566 cu. ft. 10.5 to 11 kW 50 A CLIFF 11, STEEL 11, HIVE Mini 11, CORE 11
424 to 989 cu. ft. 12 to 18 kW Two circuits HIVE 12, HIVE 15, HIVE 18

Figures are HUUM's own, from its current US manuals. The circuit column is the manufacturer's minimum: sauna heating is a continuous load, so your electrician may size the breaker and conductors larger to meet the code your area has adopted.

Before you order

Every HUUM Heater Needs Two More Things

A HUUM heater is three purchases, and the two that catch people out are not optional extras. The heater will not run without them.

If you would rather settle all three in one line, we build a sauna heater package for every HUUM electric model: the heater, a UKU control in the panel finish you pick, and the boxes of stone its manual asks for, priced at the parts added together. The three largest round heaters also carry the extension box that output needs. See every package.

A UKU control

The UKU's control unit goes outside the hot room, and its manual sets out which panel finishes can be mounted inside. The UKU Local runs the heater from the wall; the UKU Wi-Fi adds the phone app, so the room is hot when you get home. Local and Wi-Fi come in black or thermo-ash wood, and the glass, mirror and gold panels are Wi-Fi only.

One exception worth knowing: the UKU main module handles up to 11 kW on its own, so the HIVE 12, 15 and 18 need the UKU extension box as well. Nothing else in the range does, whatever a dealer listing tells you.

Sauna stone, by the box

HUUM supplies olivine diabase stone in 33 pound boxes, in two grades: 1.2 to 2 inches for the CLIFF and STEEL families, 2 to 4 inches for the DROP, HIVE and CORE. The heater sets the quantity, not the room.

A CORE takes 3 boxes. A DROP, a CLIFF Mini and a STEEL Mini take 4. A CLIFF takes 5, a STEEL or a HIVE Mini 10, and a HIVE 12, 15 or 18 takes 16. The heater may not be switched on until it is properly filled, and a sparsely filled stone bed is a fire hazard rather than a shortcut.

Add the boxes from the heater's own page and they travel with the heater at no added shipping cost. Ordered on their own, stone carries a per box shipping charge, shown in the cart before you pay. The details are on our HUUM shipping policy.

Service parts are here too, for later: DROP, HIVE and HIVE Mini and CLIFF and STEEL heating elements, and a spare UKU display panel. HUUM excludes heating elements from its warranty, so they are sold as parts rather than covered.

Close up of the stone cradle and HUUM badge on a DROP sauna heater
The stone sits in the open, in contact with the elements, on every HUUM electric heater.

The difference

What Sets HUUM Apart From Other Sauna Heater Brands

Stone in the open

Most heaters hide their elements behind a steel skin. HUUM runs them through the stone, so water thrown on the stone meets hot rock across the whole face of the heater. It is why these rooms give a softer, wetter heat than the kilowatts suggest.

A heater you are happy to look at

HUUM's own account lists international design awards across the range, the Red Dot and the European Product Design Award among them. In a small room the heater is furniture, and HUUM is one of the few brands that treats it that way.

One control across the range

The same UKU runs every HUUM heater, with the app included on the Wi-Fi version. Learn it once and it works whether you buy a DROP for a closet conversion or a HIVE 18 for a commercial room. See both UKU versions beside the other sauna controls we carry.

Listed for North America

SGS lists HUUM's electric heaters and the UKU Local and Wi-Fi controls for the United States and Canada. The certificate number is on each product page, and we will send your inspector the listing record for your model.

Stone mass rather than kilowatts

A STEEL 6 carries 330 lb of stone against 121.3 lb in a DROP 6 at the same output, and the big HIVE models carry 528 lb. More mass means the room rides out the door opening and holds its temperature through a session with several people.

Sizes that actually cover the range

From a 106 cubic foot closet conversion to a 989 cubic foot commercial room, on the same design language and the same control.

Where to start

Which HUUM Heater Suits Which Room

DROP 6, 6kW

Best for the common two to four person home sauna, 177 to 318 cubic feet. Hangs on the wall, so it takes no floor, and runs on the same 30 amp circuit as the 4.5 kW.

See the DROP 6

STEEL 9, 9kW

Best when you want stone mass on a small footprint: 330 lb of it in a 12.6 inch square body, for rooms to 460 cubic feet.

See the STEEL 9

CORE 9, 9kW

Best when the heater has to disappear into the room. Finished in alder, aspen or thermo-aspen to match your benches, or left black.

See the CORE 9

HIVE 12, 12kW

Best for a large or commercial room, 424 to 636 cubic feet, with 528 lb of stone to ride out group after group. Needs two circuits and the UKU extension box.

See the HIVE 12

Electrical and installation

What a HUUM Heater Asks of Your Electrician

Every HUUM electric heater is hardwired by a licensed electrician, on two supply circuits for the HIVE 12, 15 and 18, and the control is wired in with it. The DROP, CLIFF, STEEL and HIVE manuals call for cable meeting UL 62 in the United States or CSA 49 in Canada, no cable with non heat resistant PVC insulation, and a waterproof junction box low on the wall; the DROP and HIVE manuals also make crimped cable ends mandatory. The CORE is wired to the National Electrical Code, which is the condition SGS records against its listing.

HUUM recommends connecting its heaters without a GFCI breaker. An outdoor sauna at a home may fall inside the Code's ground fault requirement for outdoor outlets at these ratings, depending on the edition adopted and how your inspector reads it, while an indoor hardwired heater usually is not caught. Where the manual and the adopted code disagree, the code and your inspector decide.

Professional installation is a warranty condition. HUUM can ask for proof that a licensed electrician installed and connected the heater, so keep the invoice with your receipt. The room itself also has to be built for a sauna, with an insulated shell, a vapor barrier and supply and exhaust vents.

A guard is a code item rather than an upsell: the residential code asks for sauna heaters to be protected from accidental contact by a guard of a material with low thermal conductivity, such as wood, without blocking the heat. HUUM sells a rail for the DROP, CLIFF, STEEL, HIVE and HIVE Mini; around a CORE the guard is built rather than bought. Either way the heater's clearances have to be kept to the railing itself.

Buying from us

Delivery, Warranty and Returns on HUUM

How it arrives

The DROP ships as a parcel and needs nobody home. The CLIFF, STEEL, HIVE and CORE come palletized by freight, including the wall mounted CLIFF Mini and STEEL Mini, by appointment, to the curb. Stone travels in its own boxes. Full details on our HUUM shipping policy.

Warranty

Three years in a private sauna, one year in a commercial one, with elements, sensors and stone excluded. We file the claim for you rather than sending you to Estonia. The full manufacturer text is on our HUUM warranty policy.

Returns

Thirty days from purchase on a new, uninstalled heater. There is no percentage restocking fee, though a repackaging fee of 20 to 50 dollars applies, depending on the item. See the HUUM return policy for the conditions and who pays the freight.

Questions answered

HUUM Sauna Heaters: Questions Answered

Where are HUUM sauna heaters made?

HUUM is an Estonian company, founded by Siim Nellis, a third generation sauna stove producer, and its heaters are designed and built in Estonia. The DROP was developed in 2011 with the Estonian Academy of Arts and won the Red Dot product design award in 2015.

Are HUUM heaters listed for use in the United States?

Yes. SGS, which is on OSHA's list of nationally recognized testing laboratories, lists HUUM's electric heaters and the UKU Local and UKU Wi-Fi controls for the United States and Canada. The certificate number for each model is on its product page and we will send your inspector the listing record. HUUM's wood stoves hold European certification only, with no North American listing, so a local building department decides on those.

Do I need a control with a HUUM heater?

Yes, and it is a separate purchase. Every HUUM electric heater is run from a certified control mounted outside the hot room, and HUUM's matched control is the UKU, in Local or Wi-Fi form. A heater in a public sauna also has to have a timer.

Does a HUUM heater come with stones?

No. Stone is ordered by the box, and the heater sets the quantity: 3 boxes for a CORE, 4 for a DROP, CLIFF Mini or STEEL Mini, 5 for a CLIFF, 10 for a STEEL or HIVE Mini, and 16 for a HIVE 12, 15 or 18. HUUM supplies olivine diabase stone in 33 pound boxes in two grades, and the heater may not be switched on before it is properly filled.

What size HUUM heater do I need?

Measure the room in cubic feet, then add 3.3 cubic feet for every square foot of uninsulated brick, tile or glass wall, which is HUUM's rule, and count a full glass door the same way. Match that adjusted figure to the model's published range: 4 kW covers 106 to 177 cubic feet and 18 kW covers 636 to 989. If your supply is 208 volts rather than 240, size from the 208 volt figures instead, because the same heater makes less power.

What is the UKU extension box, and do I need one?

It is an extra module for heaters above 11 kW, which in this range means the HIVE 12, HIVE 15 and HIVE 18. Every other HUUM heater runs from the UKU's main module on its own. Dealer listings quote several different thresholds for it, which is where the confusion comes from.

Can I install a HUUM heater myself?

Not if you want the warranty. HUUM's warranty requires the heater to be installed and connected by a licensed electrician, with proof presented to HUUM, and HUUM recommends a specialist lays the stone. Keep the electrician's invoice.

What warranty comes with a HUUM heater?

Three years in a private sauna and one year in a commercial one, from the date of purchase, with spare parts covered for one year. Heating elements, controller sensors, stones, HUUM accessories, and wood stove door glass and ash grates are excluded. HUUM counts it as commercial use if a registered business uses the product commercially, if a private owner uses it commercially, or if a private owner runs it for more than 1,500 hours in any 12 months.

How long does a HUUM sauna heater take to heat a room?

HUUM's manuals put it at about an hour in a properly insulated room with a correctly sized heater, with the stone reaching throwing temperature at about the same time as the air.

What does a HUUM heater cost to run?

Multiply the output by your electricity rate for the ceiling: a 6 kW heater at the US average residential price of 18.3 cents a kilowatt hour, the EIA figure for June 2026, is about 1.10 dollars an hour at full draw. Once the room is at temperature the heater cycles rather than drawing full power, so a real session lands under that.

Paying for it

Financing a HUUM Order

A HUUM order is rarely the heater alone. The control, the stone and the electrician tend to land in the same month, which is why most buyers spread the cost. Shop Pay Installments is offered at checkout, with the terms and your eligibility shown once the cart is complete. There is nothing to apply for beforehand, and looking at the options does not affect your credit score.

Commercial rooms

HUUM in a Gym, Spa or Hotel Room

Two things change when the room is commercial. HUUM's warranty runs 3 years in a private sauna and 1 year in commercial use, and the code asks more of a shared room than a domestic one, including a control mounted outside the hot room and a guard where people can touch the heater.

The HIVE 18 heats the largest room in the HUUM electric range, 636 to 989 cubic feet, and it needs two supply circuits and the UKU extension box. If you are specifying for several rooms, we quote on volume and work from your drawings. Start at commercial sales or call (888) 500-5675.

Keep looking

Browse Other Categories

Where HUUM sits alongside the rest of what we carry.

Electric sauna heatersEvery electric heater we carry, all brands All sauna heatersElectric and wood burning together Heater packagesHeater, control and stone in one order Traditional saunasRooms and barrels built for a stone heater

Not Sure Which HUUM Heater Fits Your Room?

Tell us the room dimensions and how the walls are built and we will walk you through HUUM's own figures for output, circuit and stone before you order.

Find the right heater Speak with an Expert, (888) 500-5675