Sauna heater electrical checklist for Ontario: what to hand your electrician

An electric sauna heater is permanently wired to its own 240 V circuit, and in Ontario that work is regulated. Use this checklist to get the right details to your electrician before you order, so the heater, control and wiring all line up on installation day.

Who can do the work in Ontario

• Hiring someone? ESA says that if you hire anyone to do electrical work in your home, by law it must be a Licensed Electrical Contractor (LEC). Check the licence with ESA’s contractor locator. Your LEC files the notification and books the inspection.
• Doing it yourself? ESA lets homeowners do electrical work in their own home, but you must file a notification (a permit) with ESA before you start and have the work reviewed before you cover it. Friends, family members and neighbours can’t do it for you. ESA says fees for many small residential projects can be under $100.
• Check the heater maker’s rules too. Harvia, HUUM and Homecraft all say their heaters must be connected by a qualified or licensed electrician. Homecraft’s manual says a connection by a non-certified person voids the warranty.

When the work passes, ESA issues a Certificate of Acceptance. ESA calls it important for insurance and resale. Keep it with your invoice for any warranty claim.

Outside Ontario, your province’s electrical safety authority sets its own permit and inspection process, so check its rules before the work starts.

The checklist

1. The heater’s spec sheet and manual

Give your electrician the model, kW, voltage, phase and amps, plus the breaker size and minimum wire gauge from the manual’s table. Don’t size from amps alone. For example, HUUM lists a 50 A breaker and 8 AWG minimum wire for the DROP 9 kW, Homecraft lists a 50 A breaker for the Revive 9 kW, and Harvia lists a 10 AWG supply cable for the KIP 6 kW at 240 V.

2. A dedicated circuit and double-pole breaker

HUUM’s control manual calls for a dedicated circuit, and Harvia’s KIP manual calls for a standard 2-pole breaker. Our advice: label the breaker clearly so anyone can find it.

3. Wire rated for the heat

Harvia requires copper wire rated 90 °C (194 °F) for all wiring on sauna walls and ceilings, and says not to use PVC-insulated cable to connect the heater. HUUM requires a power cable that meets the CSA 49 requirements it lists for Canada, with crimped ends. Homecraft’s tables call for 90 °C copper wire.

4. GFCI: follow the manual

Harvia’s KIP manual says to use a standard 2-pole breaker, not a GFCI. HUUM recommends connecting without a GFCI breaker. Homecraft says a heater on its own circuit doesn’t need one and that GFCI breakers can nuisance-trip. Your electrician applies the Ontario Electrical Safety Code, now the 2024 edition in effect since May 1, 2025.

5. Panel capacity

At 240 V, amps = watts ÷ 240: 6 kW draws 25 A, 8 kW draws 33.3 A, 9 kW draws 37.5 A and 10.5 kW draws 43.8 A. Ask your electrician to confirm your panel has the capacity and a free double-pole space. If it doesn’t, a subpanel or service upgrade may be part of the job.

6. Where the control, sensor and contactor go

The control electronics always sit outside the hot room. Temperature limits differ by brand: Harvia wants its power unit in a dry place above 0 °C, HUUM rates its UKU main module to −40 °C in a weatherproof housing, and Homecraft sells an outdoor relay box. Distance matters too. Harvia and HUUM both limit the sensor cable to 10 m (about 33 ft), and HUUM limits its control panel cable to 20 m (65 ft). Our controls guide covers the options.

7. No outlets in the sauna room

Harvia says receptacles and plugs aren’t permitted in the sauna room, and Homecraft says not to install any. Use lighting made for sauna use, placed where the heater manual allows.

8. The outdoor run

For a backyard sauna, the feed runs from the house panel or a subpanel, underground or overhead, and it needs to be covered by an ESA notification too. Before anyone digs a trench, request locates through Ontario One Call, which applies to every job, big or small. Use outdoor-rated cable and watertight fittings; Homecraft’s outdoor box instructions mention TECK90 or equivalent.

9. Approved equipment and working safety devices

ESA requires electrical products used or sold in Ontario to carry an accredited certification mark, such as CSA, cUL or cETL. Check the label on the heater and control. Never bypass the high-limit switch or thermostat. In a 2019 safety notice on sauna fires, mostly in commercial facilities, ESA and Ontario’s Fire Marshal pointed to tampered or unapproved safety parts, combustibles left in the sauna and heaters installed too close to combustible materials.

10. 240 V or 208 V?

Most houses have 240 V single-phase power. 208 V three-phase heaters are for commercial buildings. Check before you order.

Handover sheet for your electrician

Next steps

• Choose the size first with our heater size guide or the Heater Finder.
• Browse electric sauna heaters and matching controls.
• Ask us for the manual of the model you’re considering, so your electrician can check it before you order. You pay nothing until you approve a written invoice.