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Electric furnace: the electrical side
What an electric furnace asks of the wiring: its circuit, its protection, its amps, and what the panel has to be able to carry.
In short
This guide covers the electrical side of an electric furnace: what it asks of the home’s circuit and panel.
- In the 2018 edition of the Code, an electric furnace is supplied by a dedicated branch circuit.
- Heating counts as a continuous load: the load is limited to 80% of the protection, unless the device is marked for 100% (2018 edition).
- In the example in the Régie du bâtiment du Québec’s guide, a 23 kW furnace at 240 V draws 101 A.
- Electric heating is the dominant load in a Québec home: the load calculation tells you whether the panel can keep up.
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Its own circuit
According to the Régie du bâtiment du Québec’s quality control guide (2018 edition of the Code), an electric furnace must be supplied by a branch circuit dedicated to it.
Heating loads are treated as continuous loads. To keep the heating from cutting out at the wrong moment, the connected load is limited to 80% of the protective device’s capacity, unless it is marked for 100%.
Some furnaces call for copper conductors only.
A worked example
The Régie du bâtiment du Québec’s guide gives this example (2018 edition of the Code):
| Step | Value |
|---|---|
| Furnace | 23 kW at 240 V |
| Current on the nameplate | 101 A (elements, blower motor and controls) |
| Copper conductors, at minimum | Size 3 AWG |
| Protection chosen | 150 A |
The starting point is always the appliance’s nameplate: it gives the current to supply.
That calculation is up to the electrician doing the hookup.
Is the panel enough?
An electric furnace adds the heating to what the panel already carries, and that is the biggest load in a Québec home.
In the RBQ example, the furnace alone draws 101 A. Our load calculator has an “Electric furnace” option: it tells you whether the panel can keep up, or whether you first need to go to 200 amps.
Going to 200 amps is explained in 200 Amp Panel: Is Yours Enough?.
An electric furnace to connect?
With us, the load calculation comes first, before any proposal. The price is in the quote.
Send my quote requestWith a heat pump
A central heat pump changes the equation, especially if the existing electric heating stays in place as backup. The details are in Heat pump electrical requirements.
Leaving oil heating for electricity? See Switching from oil: the electrical side.
What we do
Our part: the load calculation first, then supplying the furnace through its own branch circuit and choosing the conductors and the protection from its nameplate.
Frequently asked questions
How many amps does an electric furnace need?
It depends on the appliance: the current is written on its nameplate. In the Régie du bâtiment du Québec’s example, a 23 kW furnace at 240 V draws 101 A, and its protection is 150 A (2018 edition of the Code).
Is my 100 amp panel enough?
It has to be calculated: enter the furnace in our load calculator (“Electric furnace” option): it tells you whether the panel keeps up or whether you need 200 amps.
Does the furnace have its own circuit?
Yes. In the 2018 edition of the Code, an electric furnace is supplied by a dedicated branch circuit.
Who connects the furnace?
An electrical contractor: in Québec, electrical work is reserved for them, even for an outlet.
An electric furnace to connect?
We connect the furnace on its own circuit; the exact price is in the quote.
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Sources
Consulted on October 30, 2026.