Sauna Electrical Planning: 120V vs 240V and Circuits
This guide is for planning and purchasing. It is not installation advice; electrical work must comply with local codes and be performed by qualified electricians.
How do you calculate sauna current draw?
The core formula is simple:
Amps = total watts / supply volts
Total watts means every heater, light and accessory on the circuit. For the same wattage, doubling the voltage halves the current, which is why higher-wattage saunas move to 240 V.
| Total load | Current at 120 V | Current at 230 V | Current at 240 V |
|---|---|---|---|
| 1,500 W | 12.5 A | 6.5 A | 6.3 A |
| 2,000 W | 16.7 A | 8.7 A | 8.3 A |
| 3,000 W | 25.0 A | 13.0 A | 12.5 A |
| 4,500 W | 37.5 A | 19.6 A | 18.8 A |
| 6,000 W | 50.0 A | 26.1 A | 25.0 A |
| 9,000 W | 75.0 A | 39.1 A | 37.5 A |
Values above roughly 20 A at 120 V are impractical for household circuits, which is the practical ceiling for plug-in infrared models.
Why does the continuous-load rule matter for saunas?
The US National Electrical Code treats a load whose maximum current is expected to last three hours or more as continuous. For branch circuits with continuous loads, NEC 210.20(A) requires the overcurrent device to be rated at no less than 125% of the continuous load, which is commonly expressed as the 80% rule. Saunas are often run for long sessions and in commercial settings for hours at a time, so electricians commonly size them as continuous loads.
Applied to typical US circuits:
| Circuit | Nominal capacity | Continuous capacity (80%) |
|---|---|---|
| 15 A, 120 V | 1,800 W | 1,440 W |
| 20 A, 120 V | 2,400 W | 1,920 W |
| 20 A, 240 V | 4,800 W | 3,840 W |
| 30 A, 240 V | 7,200 W | 5,760 W |
| 40 A, 240 V | 9,600 W | 7,680 W |
| 50 A, 240 V | 12,000 W | 9,600 W |
So a 6 kW heater at 240 V (25 A) needs a circuit rated at least 31.25 A, which in practice means the next standard size up. The electrician also sizes conductors, checks the panel's spare capacity and confirms any GFCI or disconnect requirements.
When is 110-120 V the right choice?
120 V models suit North American consumers who want to avoid new wiring. They work best for one- and two-person far infrared and low-EMF cabins with modest total wattage. The limits are clear from the tables: a dedicated 15 A circuit supports about 1,440 W continuous, and a 20 A circuit about 1,920 W.
Practical guidance for 120 V products:
- Specify a dedicated circuit in the manual; shared circuits trip breakers.
- Avoid extension cords; state this in the manual and on a label.
- Keep full spectrum and red light add-ons within the circuit budget. See the full spectrum guide.
When should you move to 220-240 V?
Choose 220-240 V for larger infrared cabins, full spectrum saunas with high total wattage, every traditional electric-stove sauna, and most outdoor saunas. It is also the default supply in most of Europe, Asia, Africa and Oceania.
In North America, 240 V means a dedicated hardwired or plug-in circuit installed by an electrician. Larger commercial heaters may be three-phase. The international safety standard IEC 60335-2-53 covers sauna heaters and infrared units up to 20 kW, with rated voltage up to 250 V single-phase and 480 V for other supplies.
What is the 208 V trap in commercial buildings?
Many North American commercial buildings supply 208 V rather than 240 V. A resistive heater's output scales with the square of voltage, so a heater rated at 240 V delivers about (208/240)² ≈ 75% of its rated power on 208 V.
| Heater rated at 240 V | Output at 208 V |
|---|---|
| 4.5 kW | ~3.4 kW |
| 6 kW | ~4.5 kW |
| 9 kW | ~6.8 kW |
The heater will still work but warm up more slowly and may not reach target temperature in a large room. For hotel, gym and spa projects, ask for the building's actual supply voltage and phase, and order heaters rated for it. See choosing saunas for hotels, gyms and spas.
How does voltage affect certification?
A listing or CE declaration covers specific voltage ratings. A model certified at 120 V is not automatically covered at 240 V, and the reverse also applies. US building codes commonly require electric sauna heaters to comply with UL 875. Confirm the certified voltage for each model before ordering. The import guide covers certification in more detail.
Electrical specification checklist
- Destination voltage and frequency (for example 120 V/60 Hz, 230 V/50 Hz, 208 V/60 Hz)
- Single-phase or three-phase supply
- Total connected load in watts, including lights and audio
- Rated current at the destination voltage
- Plug type, or hardwire with junction box location
- Recommended breaker size from the supplier, to be verified by the local electrician
- Certification covering the exact voltage configuration
- Wiring diagram and terminal labels in the user manual
- Control panel and thermostat rated for the supply
- Spare heater elements matched to the voltage
Key takeaways
- Amps = watts / volts; doubling voltage halves current for the same wattage.
- Size sauna circuits as continuous loads: breaker at no less than 125% of load, or load at no more than 80% of breaker rating.
- A dedicated 15 A, 120 V circuit supports about 1,440 W continuous; larger cabins and traditional heaters need 240 V.
- 240 V heaters on 208 V supply deliver about 75% of rated output; order 208 V-rated heaters for those buildings.
- Certification is voltage-specific; confirm before ordering.
Mars sells models with 110-120 V and 220-240 V options and can configure voltage, heater layout and control panel on OEM/ODM orders. Use the sauna finder to filter by voltage, or contact us with your market's supply details.
Frequently asked questions
Can an infrared sauna run on a standard 120V outlet?
Some small infrared saunas can, if their total load fits a dedicated household circuit with headroom. A 15 A, 120 V circuit supplies 1,800 W nominally, and treating the sauna as a continuous load limits it to about 1,440 W. Larger or full spectrum models usually need a 20 A circuit or a 240 V supply.
How do I calculate the amps a sauna draws?
Divide total heater wattage by supply voltage: amps = watts / volts. A 3,000 W sauna draws 25 A at 120 V but about 12.5 A at 240 V. Then apply the continuous-load rule, sizing the breaker at no less than 125% of that current, and let a licensed electrician select the wire and breaker.
What happens if a 240V sauna heater runs on 208V?
Output drops. For a resistive heater, power scales with the square of voltage, so a heater rated at 240 V delivers about 75% of its rated wattage on 208 V. A 9 kW heater would produce about 6.8 kW, heating more slowly. Order 208 V-rated heaters for buildings with 208 V supply.
Should I order 110-120V or 220-240V saunas?
Match the destination market's mains supply and the customer's install. North American home buyers often want plug-in 120 V infrared models, while larger cabins and traditional heaters use 240 V. Most of Europe, Asia and Australia use 220-240 V. Confirm voltage, frequency and plug type on every purchase order.
