Guide

Sauna Electrical Requirements: 240V Circuit, Amps, Breaker and Wire by Heater

In the heater manuals we checked, an electric sauna heater gets its own 240-volt circuit, and the amps it draws depend on its size. Saunacraft’s spec table calls 240 V single phase “Standard Residential power in USA & Canada” and lists its home heaters from 4 kW (16.7 amps) to 15 kW (62.5 amps). Almost Heaven says the standard heaters in its kits need “between 30-40 amps with a 240V hardwired connection,” and some premium heaters as much as 60 amps. The breaker and wire size come from your heater’s manual, and makers don’t all list the same numbers for the same kW. A licensed electrician confirms the circuit and pulls the permit.

What a sauna heater needs from your panel

Paper-cut diagram of one dedicated cable running underground from a closed house panel to a disconnect box on a sauna and on to the heater — A sauna heater runs on its own 240-volt circuit from the panel — work for a licensed electrician.

Four requirements come up again and again:

240 volts, usually single phase. Saunacraft notes that 208 V “may be found” in some commercial construction and “certain high apartment density cities,” and Harvia sells The Wall in both 240 V single-phase and 208 V three-phase versions. Ask your electrician which one your home has before you order the heater.
Its own circuit. HUUM’s U.S. controller manual says the cable from the main panel must be heavy enough and to “install separate protection for the heater.”
A hardwired connection. Harvia’s U.S. manual says the heater is permanently installed and that “pigtails or plugs are not allowed in the sauna room.” Almost Heaven tells owners their electrician “will have to hard-wire the heater.”
A heater that meets UL 875. The 2024 International Residential Code (IRC), a model code, says in Section M1902 that sauna heaters “shall comply with UL 875” and be installed per the maker’s instructions. Its list of referenced standards points to UL 875—2009, “Electric Dry-bath Heaters—with Revisions through January 2021,” and Harvia’s 2022 declaration lists The Wall under “UL 875:2009 Ed.9+R:20Sep2017.” A newer, 10th edition was published in July 2024; its scope describes heaters installed under the National Electrical Code, with an automatic temperature control, a manual-reset limit control and a timer.

Heater kW to amps at 240V

Saunacraft’s table; the amps are watts divided by 240 volts.

Heater	Room size (cu ft)	Amps at 240 V	Wire size (AWG)	Breaker
4 kW wall	100–150	16.7	10	30 A
5 kW wall	150–250	20.8	10	30 A
6 kW wall	200–300	25	8	40 A
7.5 kW wall	290–375	31.3	8	40 A
9 kW wall	360–450	37.5	8	50 A
12 kW floor	450–700	50	6	60 A
15 kW floor	600–900	62.5	4	80 A

The footnote matters: “Wire and Breaker size is recommendation only. Confirm with your licensed electrician.” To size the heater for your room first, use the sauna heater calculator.

Breaker and wire size: the same kW, different numbers

Each line applies only to that maker’s heater, so we didn’t average them.

Maker and document	6 kW	≈8 kW
Saunacraft (table above)	25 A; 40 A breaker; 8 AWG	7.5 kW: 31.3 A; 40 A breaker; 8 AWG
Harvia The Wall, U.S. manual	25 A (single-group connection); minimum 10 AWG copper rated 90 °C; no breaker size in the table	33.4 A (single-group connection); minimum 8 AWG copper rated 90 °C
Almost Heaven wall heater (a Harvia heater)	“30-amp double pole breaker,” 10/2 wire; 8/2 “if the distance is greater than 90 feet”	“40-amp double pole breaker,” 8/2 wire
HUUM, U.S. controller manual (wire for the controller’s power cable)	10 AWG (4.5 and 6 kW)	8 AWG (7.5 and 9 kW)

At 6 kW, Saunacraft and Almost Heaven are a breaker size and a wire size apart. Your electrician works from the manual for the exact heater you buy, the length of the run and your local code, not from a chart like this.

More lines for your electrician:

Copper, rated 90 °C. Harvia and Almost Heaven both specify copper wire with 90 °C insulation; Almost Heaven’s barrel manual adds “Do not use aluminum wire.”
GFCI: ask your electrician before you buy. Several heater makers’ manuals say not to put the heater on a GFCI or RCD. Harvia’s U.S. manual: “Do not connect the power feed for the heater through the RCD (residual current device)/GFI (Ground Fault Interrupter)!” Almost Heaven’s wall heater manual: “Do not use GFCI with this heater.” SaunaFin’s barrel instructions, for the Helo Cup heater: “Do NOT use a G.F.I breaker.” HUUM’s controller manual recommends connecting it without a residual-current device (RCD). Local ground-fault rules for outdoor circuits can differ, so your electrician and inspector decide how your sauna’s circuit is protected.
A way to cut all power. HUUM: “A method to disconnect all poles from the mains (a circuit breaker) must be installed.”

Panel capacity and upgrades

Whether your panel has room for this breaker is the electrician’s call. Fixr (updated January 2025) describes the basic job as a 220-volt circuit in the home’s existing panel with a receptacle near the sauna and says “most electricians charge from $500 to $800 depending on the complexity of the wiring and the materials needed.” That assumes the panel can take the circuit, and Harvia’s manual calls for a hardwired heater, not a plug-in one, so get a quote for the job your manual describes. For the full budget, see outdoor sauna cost.

Outdoor runs to a backyard sauna

Almost Heaven’s barrel manual says electrician costs “can vary greatly” with the sauna’s distance from your electrical service box, where you live and the cost of materials, and recommends quotes “from 2 to 3 different licensed electricians.” Distance can also change the wire: Almost Heaven’s wall heater manual recommends 8/2 instead of 10/2 wire for its 6 kW heater when the run is longer than 90 feet, “to accommodate for voltage drop.”

The cable route, depth, conduit and disconnect are for the electrician and your local code. If anyone digs a trench, call 811 “a few business days before you begin any digging,” and wait until all utilities have marked their lines. If the base isn’t built yet, plan the cable route together with the sauna foundation.

Almost Heaven’s barrel light plugs into “a standard 110V outlet,” or your electrician can hardwire it to a 110 V circuit. Its Harmony infrared manual (an indoor model) calls for a “120VAC 15AMP Dedicated Circuit” for the 2-person model and 20 amps for the 3-person. See infrared vs traditional saunas.

Permits and a licensed electrician

Every heater and sauna manual we read puts the wiring with a professional. Harvia: “Wiring must be done by a licensed electrician.” Almost Heaven’s barrel sauna manual: “All electrical wiring must be performed by A QUALIFIED LICENSED ELECTRICIAN.” HUUM: the electrical work “must be carried out by a certified electrician.” Harvia’s U.S. manual also tells the electrician to ground the heater and control unit “as per NEC and local codes.” Your local building department decides which code edition and permits apply. Fixr’s cost guide says, “With an outdoor sauna, you need to have a permit”; your building department has the final word.

Hand the electrician the heater’s model, kW, voltage and manual (plus the control unit’s manual), the distance from your panel, and any light or fan you want. Harvia: “Receptacles OR PLUGS are not allowed in a Sauna room.”

A wood-burning stove needs no heater circuit but brings its own rules; see wood-burning vs electric saunas.

Sizing a heater or pricing a setup? Run the Sauna Planner — volume, kW, breaker and cost in one place.

Illustrations on this page are AI-generated to help you picture the situation. They are not photos of real homes, jobs or people.

Sources

Updated 2026-11-02

Safety and permits

A sauna heater needs its own circuit sized to the maker's manual — have a licensed electrician wire it and pull the permit. Wood-burning stoves need the clearances and chimney in the stove's manual and local code approval. Before digging for a foundation, call 811. This site doesn't give medical advice: if you're pregnant or have a health condition, ask your doctor before using a sauna.