Traditional sauna heaters: sized by kW, wired at 240 V
A traditional sauna heater warms the air to 160 to 194 °F and heats a load of stones that make steam when you pour water on them. The room's volume sets the kilowatts, the kilowatts set the current, and the current sets the breaker and cable. Nearly every heater runs on 240 V and is wired straight to its own breaker.
Where the controls live, and how much stone
Output is the first choice and the sizing calculator handles it. The other differences are practical.
Simplest wiring
Controls on the heater
Thermostat and timer dials on the heater itself, like the Harvia KIP. One cable from the breaker to the heater. You set the temperature inside the hot room.
Wall panel or app
Separate control
A control box outside the room switches the heater, often with WiFi. HUUM's UKU and Harvia's Xenio work this way. More wiring, and the room can be warm when you walk in.
Heat and steam
Stone mass
A KIP holds a 44 lb box of stones, a HUUM Drop about 121 lb and a Cilindro up to 200 lb. More stone takes longer to heat and holds more heat for steam.
Rare
120 V heaters
A 120 V heater tops out near 2 kW, enough for about 100 cubic feet. Harvia's Vega Compact 1.9 kW and Finnleo's Junior run on 120 V; on Amazon only VEVOR sells one with an offer.
Quick picks
The short answer for common situations. Each links to the full card below.
A 2 kW heater for a one-person room on 120 V, hard-wired.
Compare the eight
Room volume, current and cable from each maker's US installation manual. The Finlandia's figures come only from its Amazon listing, and VEVOR's current is calculated from its wattage, since its manual prints none.
Product links on this page go to Amazon. If you buy through them, Which Sauna earns a commission. How we pick and earn
Harvia's stainless wall heater with the thermostat and timer dials on the unit, so no separate control box is needed. The 4.5 kW size covers 100 to 210 cubic feet, a small one- or two-person room.
Room
100–210 ft³; 16–30 ft² of floor
Power
240 V single phase, 18.8 A
Cable
10/2, copper rated 90 °C (manual)
Stones
44 lb box, included (listing)
Room height
75 in minimum
Listing
UL marked; complies with UL 875 (manual)
Suits: A small indoor room or barrel up to about 210 cubic feet, on a 240 V circuit.
Weigh: Hard-wired only; the manual says "no pigtails or plug allowed" and "Do not use a ground fault circuit interrupter (GFCI)". The timer shuts it off after 60 minutes, with a delayed start up to 8 hours.
The same heater at 6 kW, for 170 to 300 cubic feet. That band covers most four-person indoor rooms and outdoor barrels, which is why barrel kits from Almost Heaven, Redwood Outdoors and ALEKO ship a KIP.
Room
170–300 ft³; 28–40 ft² of floor
Power
240 V single phase, 25 A
Cable
10/2, copper rated 90 °C (manual)
Clearance
4 in minimum to the wall
Room height
75 in minimum
Listing
UL marked; complies with UL 875 (manual)
Suits: A two- to four-person room in the 170–300 cubic foot band.
Weigh: At 25 A it needs its own 2-pole breaker and 10-gauge copper. A room under 170 cubic feet belongs on the 4.5 kW.
The largest KIP, for 250 to 425 cubic feet. It moves to 8-gauge cable at 33.3 A, which is the step where the electrical cost of a bigger room shows up.
Room
250–425 ft³; 40–65 ft² of floor
Power
240 V single phase, 33.3 A
Cable
8/2, copper rated 90 °C (manual)
Clearance
5 in minimum to the wall
Listing
UL marked; complies with UL 875 (manual)
Suits: A five- or six-person room, or a room with a lot of glass that counts as extra volume.
Weigh: The Amazon listing mentions a one-year warranty; Harvia's current US terms give five years residential on heaters and controls, with one year on elements and stones.
A second 6 kW wall heater with dials on the unit, rated for the same 170 to 300 cubic feet as the KIP-60. Amazon also carries a Finlandia/Harvia FLB-80 listing, which points to a Harvia-built heater under the Finlandia name.
A tall steel cage that holds up to 200 lb of stones around the elements. The mass of stone takes longer to heat and gives a softer, longer steam than a wall heater. Harvia rates the 9 kW for 141 to 494 cubic feet.
Room
141–494 ft³; 23–79 ft² of floor
Power
240 V single phase; 37.5 A one group, 25 A each in two
Cable
8 AWG one group, 10 AWG two groups (manual)
Stones
Up to 200 lb
Size
14 × 13 × 40 in
Listing
ETL to UL 875
Suits: A larger room, or a buyer who wants a lot of stone and floor space to stand it on.
Weigh: Wired as one group it draws 37.5 A and needs 8-gauge copper; split into two groups it is 25 A per circuit on 10 gauge. Amazon shows it from other sellers, with no featured offer.
An Estonian heater with an open steel frame that holds about 121 lb of stones on the wall. The bundle includes HUUM's UKU Local control, which mounts outside the room. HUUM is the one heater maker here that prints the breaker size: 30 A for the 6 kW.
Room
177–318 ft³ (US manual)
Power
240 V, 25 A; 30 A breaker
Cable
10 AWG minimum (manual)
Stones
About 121 lb; 143 lb with the heater
Control
UKU Local, separate box
GFCI
Maker recommends connecting without one
Suits: A 177–318 cubic foot room, and a buyer who wants the stone mass of a pillar heater on the wall.
Weigh: With stones it puts 143 lb on one wall, so the framing behind it matters. No UL, ETL or CSA mark appears on HUUM's site or in the manuals read; the IRC asks for UL 875, so check the rating plate. HUUM's own warranty is 3 years for private use, elements excluded.
The price floor for a 6 kW heater: the same kilowatts and room band as the KIP-60, with knobs for temperature and a 3-hour timer. VEVOR's manual sizes it for 5 to 9 cubic metres.
Room
5–9 m³, about 176–318 ft³ (manual)
Power
"220/60" (manual); 25 A at 240 V (calculated)
Stones
10–15 kg, about 22–33 lb (manual)
Controls
Knobs, 3-hour timer
Listing
None stated
Suits: A buyer weighing cost against documentation and listing for a 6 kW room.
Weigh: No safety listing is stated, and the manual gives no amps, breaker or wire gauge. The 230 °F maximum is VEVOR's figure and sits above the IRC's 194 °F room limit. One-year guarantee.
One of very few traditional heaters on Amazon that runs on 120 V, sized for 53 to 88 cubic feet, a one-person room. VEVOR says it has no plug and must be hard-wired by a licensed electrician on 12-gauge cable.
Room
53–88 ft³, 1.5–2.5 m³ (seller)
Power
120 V, 2,000 W; 16.7 A (calculated)
Wiring
Hard-wired, 12 AWG, "20 amps or more" (seller)
Stones
22–33 lb, not included
Size
16.1 × 10.6 × 22.4 in
Listing
None stated
Suits: A very small room where a 240 V circuit is out of reach.
Weigh: At 16.7 A it is a continuous load over 80% of a 20 A circuit, so the circuit question goes to the electrician. Asked for a UL, ETL or CSA listing, VEVOR answered only that it is FCC certified, which covers radio emissions. Stones are extra.
The International Residential Code's sauna heater section (M1902 in the 2018 and 2021 editions) has a short list of rules. The heater must be installed as its manufacturer instructs and comply with UL 875, the standard for electric sauna heaters. It needs a guard of low-conductivity material, such as wood, against accidental contact. And its thermostat must hold the room at 194 °F (90 °C) or less; where the thermostat is separate from the heater, its sensor goes within 6 inches of the ceiling.
That makes the safety listing a practical question. Harvia's KIP is UL marked, and its Cilindro carries ETL certification to UL 875. HUUM's site and manuals show CE and other European marks but no UL, ETL or CSA mark, and VEVOR states none. Your inspector will look for one on the rating plate.
Sold off Amazon
These heaters have no Amazon offer today, and their manuals fill gaps in the table above.
Finnleo's Junior appears to ship only with Finnleo's own rooms, and Harvia's site now lists only the 3.5 kW Vega Compact, so the 120 V versions may be hard to find.
Stones, and how much each heater takes
Stone load by heater
Heater
Stones
Harvia KIP
One 44 lb box
Harvia Vega Compact
28.5 lb
HUUM Drop
About 121 lb
Harvia Cilindro 9 kW
Up to 200 lb
VEVOR 2 kW
22–33 lb, not included
Harvia's AC3000 box is olivine diabase in 2 to 4 inch pieces, which is what the KIP, Vega and Cilindro are built around. Most heater bundles on Amazon include stones; VEVOR's do not.
Bucket, ladle and a room thermometer
A thermometer near the ceiling shows what the room actually reaches, which is the number the code's 194 °F limit refers to. The heater dial only shows where the thermostat is set.
Room thermometer and humidity gauge
Northwood Sauna thermometer and hygrometer
Northwood Sauna 2-in-1, Canadian red cedar
Two dials in a red cedar frame, reading in Fahrenheit and Celsius. A room gauge is how you check the actual air temperature against the heater's dial.
A red cedar bucket and ladle from the Harvia-owned barrel maker, sold with or without a matching thermometer. Almost Heaven sells only accessories on Amazon; its saunas are sold direct.
