Sauna Heaters

Most people shopping for sauna heaters for sale start with kilowatts and price. Neither is where the decision goes wrong. It is the stone: two heaters at the same nine kilowatts hold 44 pounds of rock or 330, and that is what you feel on the bench. We carry electric and wood-burning heaters from 1.9 to 40 kW, factory-authorized. Call (888) 500-5675 with your dimensions and we'll size it with you.

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Sauna Heaters: How to Choose the Right One for Your Room

You ladle water across the top stones and the room answers in about two seconds. That's the whole thing. Everything on this page is in service of those two seconds, and the heater is what decides whether you get them.

Two heaters with the same kilowatt rating can behave completely differently, because the rating tells you how fast the room heats and the stone tells you how the steam feels. Only one of those is printed on the box.

There are four decisions. Electric or wood. What output the room needs. Whether the controls live on the heater or on the wall. And how much stone sits between the elements and the air.

Electric pillar sauna heater loaded with stones in a glass-fronted sauna room
4 cu. ft.Added load per sq. ft. of glass
x 1.5Volume multiplier for log walls
44 to 330 lbStone capacity at the same 9 kW
194°FRoom temperature cap in the code

The first decision

Electric Sauna Heater vs. Wood-Burning Stove

Two options, and the building usually decides for you.

If there's a panel with capacity near the sauna, electric is simpler in every way. If there isn't, or the room sits at the end of a garden with no trench dug, wood stops being the romantic choice and becomes the practical one. If you're still deciding between a traditional room and infrared before you get to heaters at all, start with infrared vs. traditional saunas.

Electric

Hardwired to its own circuit, set by a timer and thermostat, and it comes up to temperature without anyone tending it. Almost every indoor sauna uses one. The trade is that it needs real electrical capacity, and the wiring cost steps up at the top of the range. Full detail on electric sauna heaters.

Wood-burning

No circuit, no controller, no power bill. You tend a fire rather than set a dial, which for a lot of people is the entire appeal. The costs are a chimney, a floor plate, clearance to anything combustible and somewhere dry for logs. Budget all four with the stove. Full detail on wood-burning sauna stoves.

Wood-burning sauna stove alight with a basket of split firewood beside the bench
The wood option, with the part of it people forget: somewhere dry to keep a season of logs.

A third option exists on some electric models: a combination heater with a small water reservoir, so the same unit runs as a dry Finnish sauna or with steam added on top of the dry heat. It still runs at sauna temperature rather than steam-room temperature, so it isn't a substitute for a steam room.

How long either takes to get hot

Both manufacturers who publish a figure put a correctly sized electric heater in a well-insulated room at about an hour to reach bathing temperature. A tightly built small room does it faster. The practical difference with wood isn't really the clock, it's that the electric hour happens on a timer while you finish dinner and the wood hour needs you outside with it.

Sizing

What Size Sauna Heater Do I Need?

Seven output bands, and the two wall materials that move a room up one.

Measure the room in feet and multiply length by width by height. That volume is what output is rated against. Floor area on its own tells you nothing, which is why a tall room with a small footprint catches people out.

Swipe the table to see every column.

Room volume Typical output What that room looks like
Under 110 cu. ft. 1.9 kW Converted closet, one person. The only size that plugs into a normal outlet.
70 to 160 cu. ft. 3.5 kW One or two person cabin. Hardwired, despite the small output.
100 to 210 cu. ft. 4.5 kW Small indoor room, one or two people
170 to 300 cu. ft. 6 kW Two to four people. The most common home size.
250 to 425 cu. ft. 8 kW Four people, or a smaller room with a lot of glass
280 to 500 cu. ft. 9 kW Large home sauna, four to six people
320 to 640 cu. ft. 10.5 kW Very large home room, or light commercial
550 to 880 cu. ft. 15 to 16 kW Commercial room in a gym or spa

Only the smallest band plugs in. Everything from 3.5 kW upward is a hardwired appliance on its own circuit. A 3.5 kW heater would draw around 29 amps at 120 volts, which no household outlet carries, so it's built as a 240 volt unit. The amperage, conductor size and circuit count for every band are set out under amperage and circuits.

Glass and stone change the answer

Insulated timber walls hold heat. Glass, tile, brick and bare concrete don't, and a room with a full glass front behaves like a considerably bigger room. The manufacturer's adjustment is roughly four cubic feet of extra load for every square foot of uninsulated surface. A large glass door on its own can move a borderline room into the next output up.

Uninsulated log walls are the extreme case, because log heats slowly. The published rule is to multiply the room volume by one and a half before you look at any sizing chart at all. A log cabin sauna measuring 400 cubic feet is a 600 cubic foot sizing problem.

Between two sizes, go up. But not two sizes up. An undersized heater runs constantly and never charges the stones, which is what people mean when they say a sauna is hot but the steam is disappointing. An oversized one cycles off before the stone pile is charged and gives you the same complaint from the opposite direction. The published range for each heater is where it actually performs.

Stone capacity

How Much Stone a Heater Holds, and Why It Changes the Steam

Three capacity bands. The same nine kilowatts holds 44 pounds or 330, and you feel every pound of it.

We ask every caller how much stone their heater holds. Almost nobody knows, and it's on the spec sheet of every model we sell. Two nine kilowatt heaters, same output, same running cost: one carries 44 pounds of rock and another carries 330. That difference is what you feel on the bench.

Stone is a battery. It absorbs heat while the elements run and releases it once they cycle off, so a large stone mass holds temperature more evenly through a long session and recovers faster after each ladle. It also changes the character of the heat, because radiant warmth off rock is softer on skin than the same energy off exposed metal.

Around 40 lbs

Typical of compact wall-mounted heaters. Heats a small room quickly and cheaply. The steam is sharper and shorter lived, and the room cools faster between ladles.

90 to 130 lbs

The middle of the market and the sweet spot for most home saunas. Enough mass to hold a steady room without needing a heavier circuit or a bigger footprint.

150 lbs and up

Pillar and basket designs that put stone in contact with the elements down the full height of the column. The softest steam available from an electric heater, and the reason people pay more for them.

Capacity follows the design, not the fuel. A large electric pillar heater can hold more rock than a wood stove, and frequently does. Compare the published figure for the specific models you're choosing between rather than assuming wood wins.

Stone shape is set by your heater, not by a general rule

This one is worth reading twice, because getting it wrong can cost you a warranty. One manufacturer's pillar heater manual calls for angular split-face stones. The same manufacturer's US wall heater manual forbids cleavage-surface stones and requires rounded ones. Both are correct for their own model. Read the manual for the heater you actually buy.

What is consistent across brands: size them roughly two to four inches, buy stones sold for sauna use rather than landscaping rock, and stack loosely so air moves through the pile instead of packing it tight. Manufacturers are explicit that unsuitable stones void the warranty.

Harvia pillar sauna heater packed with stone, seen from above
A pillar heater holds stone the full height of the column, not just a tray on top. That is where the difference in steam comes from.

Stones are almost never included. Depending on the heater you may need one box or thirteen, they're heavy, and they're priced and shipped separately. Ask us to quote them on the same order. Restack at least once a year, more often with heavy use, and replace individual stones as they crumble. Manufacturers tie replacement to condition rather than to a calendar.

Controls

Do You Need a Separate Control Unit?

One question, and it decides whether the room can be hot before you get home.

Some heaters carry a timer and thermostat on the body. Others run from a control unit mounted outside the hot room, which is a separate purchase with its own wiring run and its own maximum load rating. On-board controls generally top out around eight kilowatts, so above that the question answers itself.

Manufacturers signal which is which in the model code, and the conventions aren't consistent between product families. Confirm rather than assume, or see the full comparison on the electric heater page.

One correction worth making, because it usually gets filed under commercial. Where the mechanical code is adopted, a timer controlling the heater has a maximum operating time of one hour and its control must sit outside the sauna room, and the residential code requires a thermostat limiting the room to no more than 194 degrees Fahrenheit. Those reach domestic saunas too.

Running cost

What a Sauna Heater Actually Costs to Run

Running cost is the number this category almost never publishes, so here it is with the method.

A heater draws its rated output while it brings the room up, then cycles to hold temperature, so it isn't pulling full power throughout. A reasonable estimate is full load through heat-up and roughly a third of the time after that.

So: a six kilowatt heater, an hour to come up and a forty minute session, comes to about seven kilowatt hours. Multiply by your own rate per kilowatt hour and you have your number. Rates vary enough across the country that any figure we printed would be wrong for most readers.

Two things move this more than the heater does. A well-insulated room with a solid door cycles far less than one with a large glass front. And stone mass helps, because a charged pile carries the room while the elements are off. Financing is available if the up-front number rather than the running cost is the obstacle, through monthly payment options.

Wood-burning stoves have no running cost beyond the wood, which for anyone with access to seasoned timber rounds to nothing. The trade is your time, and a chimney that has to be inspected annually.

Installation

Wiring, Clearances and Code

Four requirements, and two of them get described as optional when they aren't.

A licensed electrician, with paperwork

Every electric heater above the smallest plug-in models is hardwired, and installation by a licensed electrician is a warranty condition. Both major manufacturers in this range go further than a general instruction: their published warranty terms require that proof of professional installation is presented before a claim is honored. Keep the invoice.

Clearances are model-specific and enforceable

Every heater publishes minimum distances to side walls, ceiling, benches and anything combustible. These aren't guidelines. They're part of what the unit was tested and listed against, and an inspector can fail an installation that ignores them. Check the published figures against the actual corner you plan to use before ordering, because the difference between a three inch and a six inch side clearance can rule a model out of a small room.

The guard rail is required, not recommended

This gets sold as an accessory and it isn't one. The residential code requires a sauna heater to be protected from accidental contact by a guard of material with low thermal conductivity, such as wood, and the mechanical code says the same. Manufacturers' own manuals describe the heater fence as necessary for safety and specify softwood, fixed to the wall, kept below the rock line. Most makers sell one built for their heater. Price it with the heater.

The code caps sauna room air at 194 degrees Fahrenheit. The heater casing and the stones run far hotter than that, which is the entire reason the rail exists.

Circuits, briefly

Fixed electric heating is a continuous load, so conductors and protection are sized above the running current rather than at it. Most home-sized heaters run on a single circuit, including the nine and ten and a half kilowatt models that are often wrongly described as needing two. The published amperages, conductor sizes and the point where a second circuit genuinely starts are all on the electric page.

Worth knowing this year. The safety standard these heaters are listed to is changing. A new standard for sauna heaters was published in mid 2025 to replace the long-standing one, and it brings real differences, including a longer permitted run time and a different position for the temperature sensor. The catch is that the 2024 mechanical code still names the old standard by number. A heater listed only to the new one can be questioned by an inspector working from that code edition. If you're building this year, ask your inspector which edition your jurisdiction has adopted before you order, and ask us what a specific heater is listed to. Call (888) 500-5675.

Airflow

Ventilation, and Why the Manufacturers Disagree

The part most builds skip, and the part where following the wrong diagram costs you the steam.

A sauna needs air moving through it. Without it the room stratifies, the air near the bench goes stale, the heater works harder than it should, and the timber stays damp between sessions. If a room feels stuffy rather than hot, or the heat sits at the ceiling while the bench stays cool, check ventilation before you blame the heater. It's the more common cause.

The two manufacturers do not agree, so follow your own manual

This gets published as settled and it isn't. One manufacturer places the exhaust low, near the floor and as far from the heater as the room allows, with a second vent near the ceiling that stays closed during heating and bathing and is opened afterwards to dry the room. Its own maintenance instructions note that the room heats faster with that high vent shut. The other specifies the opposite: exhaust on the wall opposite the inlet, at least eight inches higher than it.

Both work. What doesn't work is running the first arrangement with the high vent open during a session, which is a common build error and reads exactly like an undersized heater.

The inlet depends on your extraction

Under gravity ventilation the inlet sits below or beside the heater, so incoming air is warmed as it arrives. Under mechanical extraction it goes above the heater instead. That isn't a preference, it's a different diagram in the same manual.

Where the mechanical code is adopted you also owe a ventilation opening near the top of the sauna door, roughly four by eight inches. That applies to domestic rooms as well as commercial ones.

Before you order

Eight Checks That Prevent Most Problems

All eight are cheaper to settle now than on the day the crate arrives.

  • Measure the room in cubic feet, not square feet, and write the number down.
  • Measure the glass, tile, brick or bare concrete, and add four cubic feet per square foot.
  • Multiply by one and a half if the walls are uninsulated log.
  • Confirm your supply: 240 volt single phase, or 208 volt three phase.
  • Confirm panel capacity, and whether that model wants one circuit or two.
  • Decide whether you want to start the room remotely, which decides the control unit.
  • Order stones with the heater, in the quantity that specific model takes, and the guard rail with it.
  • For a wood stove, price the chimney, the flue adapter and the floor plate at the same time.

Ceiling height is worth a second look. Most heaters specify a minimum room height, and rooms much above eight feet waste heat above head level. Dropping a high ceiling is usually cheaper than buying a bigger heater to compensate.

Types compared

Sauna Heater Types Compared

Six formats, and the column buyers skip.

Swipe the table to see every column.

Type Mounting Typical output Stone Best for
Compact wall Wall 1.9 to 4.5 kW Low Closet conversions and one-person rooms. Only the smallest plugs in.
Standard wall Wall 4.5 to 8 kW Moderate The default home heater. Simplest to install, keeps the floor clear.
Pillar Floor or wall 6 to 10.5 kW High Anyone who cares how the steam feels. Stone in contact top to bottom.
Basket or floor Floor 9 to 20 kW High Large rooms and commercial installations.
Combination Floor or wall 8 to 10.5 kW High One room that runs dry, or with steam added on top of the dry heat.
Wood-burning Floor 14 to 40 kW Varies widely Outdoor cabins, off-grid sites, and anyone who wants the fire.

Wood stoves are sized by room volume, and most manufacturers publish a kilowatt output alongside it, which is why you'll see kW figures in the wood stove titles. Output ranges overlap because build quality changes the answer: an insulated room with a solid wooden door sits at the bottom of its band, the same room with a full glass front sits at the top.

Who we sell to

Who Buys Sauna Heaters From Us

Three calls we take constantly, and what changes in each.

Replacing a failed heater

The most common call. An element or a thermostat has gone on a ten-year-old unit and the room is already the right size. Bring us the old model number and the room dimensions and we'll match it or improve on it.

Building a room from scratch

Usually a garage, a basement or a garden cabin. These calls take longer, because the heater, the control, the stones, the ventilation and the electrical work all need deciding together. That's what we're for.

Gyms, spas and hotels

Commercial duty changes the warranty, the code requirements and often the electrical supply. We quote on volume and work from drawings. Start at commercial sales, or see commercial saunas.

Staff picks

Four Heaters We Recommend Most Often

Chosen for the four situations we're asked about most. All four are Harvia sauna heaters, because that's the range we carry.

Most home saunas

Harvia KIP

The wall format, and the one most replacement calls end up on. Controls on the body, so no second box to wire.

See the KIP range

Best steam

Harvia Cilindro

Pillar format. Carries several times the rock of a wall unit at the same output, which is the whole argument of the section above.

See the Cilindro range

Commercial

Harvia Club

The commercial range, with three phase versions for buildings that have it. Specify with your electrician rather than off a spec sheet.

See the Club range

Off-grid

Harvia Pro 20

Where the answer to the first decision was wood. Sized for most six person cabins, and available loading through the wall.

See the Pro 20 range

Questions answered

Sauna Heaters: Frequently Asked Questions

Electric or wood-burning: which should I choose?

The building usually decides. If there's a panel with capacity near the sauna, electric is simpler in every way: it runs on a timer, needs no chimney and asks nothing of you between sessions. If getting a heavy circuit to the sauna means trenching a garden, wood becomes the practical choice as well as the atmospheric one. Wood also brings a chimney, a floor plate and a flue adapter, all of which should be priced with the stove rather than after it.

What size sauna heater do I need?

Multiply room length by width by height in feet to get the volume, then match that against the heater's published range. As a guide, 170 to 300 cubic feet suits a 6 kW heater and 250 to 425 suits an 8 kW. Add roughly four cubic feet of extra load for every square foot of glass, tile or bare concrete, and multiply the whole volume by one and a half if the walls are uninsulated log. Between two sizes, choose the larger, but don't jump two.

Are sauna stones included with the heater?

Almost never. Stones are heavy, they're priced separately, and the quantity is set by the heater rather than the room. Across the range that runs from a single 44 pound box on the smallest wall heater to thirteen boxes, over 570 pounds, on the largest wood stove. Order them at the same time as the heater. Use stones sold for sauna use, sized roughly two to four inches, and check your model's manual for the shape it requires, because manufacturers differ on rounded versus split-face and unsuitable stones void the warranty.

How long does a sauna take to heat up?

Both manufacturers who publish a figure put a correctly sized electric heater in a well-insulated room at about an hour. A small, tightly built room does it faster, and a room with a lot of glass takes longer. Wood stoves are comparable, but no manufacturer in that category publishes a figure. If a room consistently takes far longer than an hour, the usual causes are an undersized heater or inadequate ventilation, and ventilation is the more common one.

Is a guard rail required around a sauna heater?

In most of the country, yes. The residential code requires a sauna heater to be protected from accidental contact by a guard of material with low thermal conductivity such as wood, and the mechanical code says the same. Manufacturers' own installation manuals describe the heater fence as necessary for safety. Most makers sell one built for their heater, and it should be on the same order.

What does a sauna heater cost to run?

Take the output in kilowatts and multiply by the hours you run it, allowing for the fact that it cycles rather than drawing full power throughout. A 6 kW heater, an hour of heat-up and a forty minute session, comes to about seven kilowatt hours. Multiply by your own rate. Insulation and stone mass affect the answer more than the brand does.

Can I install a sauna heater myself?

No. Every heater above the smallest plug-in models is hardwired and must be installed by a licensed electrician. Both major manufacturers in this range require that proof of professional installation is presented before a warranty claim is honored, so keep the invoice. Cable inside a sauna wall also has to be rated for the temperatures it will see, and clearances to combustible surfaces are model-specific.

Do you sell heaters for commercial saunas?

Yes. Commercial rooms usually need higher output, often on 208 volt three phase, and code asks more of them, including a timer with its control outside the sauna room. Warranty terms are also shorter on commercial duty. We quote on volume and work from drawings, so start at commercial sales or call us.

Related

Browse Other Categories

Where heaters sit alongside the rest of what we carry.

Electric sauna heatersAmperage, phase, circuits and controls Wood-burning sauna stovesFlue, clearances and permits HarviaThe full range from one manufacturer Traditional saunasRooms built for a stone heater

Sauna use carries risks for some people, and there is more on the evidence and the cautions on our saunas page. Read our full Medical Disclaimer.

Not sure which heater your room needs?

Send us the dimensions, the wall build and how much glass you have. We'll tell you the output, whether it needs one circuit or two, how many boxes of stone to order with it, and what else has to be on the same pallet.

Speak with an Expert, (888) 500-5675 Buying for a business?