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Standby generator: what drives the price

Size in kilowatts, automatic transfer switch, propane or natural gas, location and maintenance in Québec: what to know before installing a standby generator.

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By the master electricians of STM-ÉlectriqueRBQ licence 5815-0137-01Sources checked on October 4, 2026

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In short

An automatic generator starts on its own when the power goes out, and the house goes back to the grid when it returns.

At STM-Électrique, the price of the installed automatic transfer switch is in the written quote, free of charge. The generator, its base and the fuel are extra.
It runs on propane or natural gas, never on gasoline. The gas part is done by a licensed gas contractor.
In Québec, the equipment must be approved for Canada. Some Generac packages, those sold with the 200 A smart switch, are certified for the United States only.
In cold weather, Generac calls for an oil change every year or every 100 hours.

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During an outage
Size
A few circuits or the whole house
Installed cost
Where to put it
Who does what
Propane or natural gas
Maintenance
Frequently asked questions

What it does during an outage

A portable generator has to be taken out, started and plugged in, preferably not in the middle of the night. An automatic generator does all that on its own, whether you’re home or not. This guide explains what we install, what drives the price and what Québec requires. The brand we install most often is Generac: the figures that follow come from its spec sheets.

The heart of the system is the automatic transfer switch, installed near your panel. According to Generac’s spec sheet:

it monitors the grid voltage constantly;
when it drops below 65% of normal, it waits a short delay, factory-set at 5 seconds, then starts the generator;
after a warm-up of about 5 seconds, it switches the house over to the generator;
when the grid comes back above 80%, it switches the house back to the grid, and the generator runs about one minute with no load to cool down before stopping.

The whole time, the switch guarantees that your house is never connected to the grid and the generator at the same time. That’s what keeps the generator’s current from flowing back to the grid, a danger for line workers: our guide on the transfer switch explains it in detail.

Which size to choose

Generac’s Guardian series residential generators range from 10 to 26 kW. Their output depends on the fuel: on natural gas, it’s generally lower than on propane (the 14 kW model is an exception, according to the spec sheet). Generac indicates a typical loss of 10 to 20%.

Model	On propane	On natural gas
10 kW	10,000 W	9,000 W
14 kW	14,000 W	14,000 W
18 kW	18,000 W	17,000 W
20 kW	20,000 W	18,000 W
22 kW	22,000 W	19,500 W
24 kW	24,000 W	21,000 W
26 kW	26,000 W	22,500 W

There’s no reliable “this house, this size” chart. Generac itself says its 22 kW model can power the whole house for many homes, not all of them. The right size comes from a load calculation done by the electrician, based on what you want to keep running, heating included.

A few circuits or the whole house

Two ways to go, depending on the switch:

	Essential circuits	Whole house
Switch	100 A, limited circuits (16 spaces)	200 A, approved as service equipment
What is backed up	The circuits chosen with you	The whole panel
Generator	Smaller	Larger, or load management

To back up the whole house without buying the largest generator, Generac offers load management: modules temporarily shut off large appliances to avoid exceeding the generator’s capacity. We choose a switch and load management that carry a Canadian certification.

Watch out for packages with a smart switch. Generac’s spec sheets indicate that the packages sold with the 200 A smart switch are certified for the United States only. In Québec, the equipment must carry the label of an organization recognized in Canada. At STM-Électrique, we install only equipment certified for Canada.

Installed cost

The total price of an automatic generator has three parts:

Part	What drives the price	At STM-Électrique
The automatic transfer switch, installed	Specified in the quote, after the visit	Price in the quote
The generator	Its size, the model	Depending on the model chosen, priced in the quote
The gas connection, the pad, the permit if any	Priced by the gas contractor; the permit depends on the municipality	The gas is done by a gas contractor

A serious price is given after seeing the panel, the location and the gas supply.

Rénoclimat: up to $1,000 for the hookup. Since October 1, 2026, Rénoclimat pays up to $1,000 toward the labour of a master electrician who connects a backup power source to the panel of your principal residence, a duplex, a triplex or a building with at least four units. The Québec government describes this measure as connecting a backup power source “powered by renewable energy”: for a generator, have Rénoclimat confirm it qualifies before counting on this rebate. The home must have been built and lived in for at least five years. The rebate doesn’t cover buying the generator or the transfer switch. You apply yourself, no later than 12 months after the work. Rénoclimat 2026: up to $1,000 to hook up a backup power source

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Where to put it

The generator goes outdoors, on a non-combustible, level base (gravel, crushed stone or a concrete slab). Generac’s minimum clearances:

3 feet (0.91 m) in front and on each side, shrubs included;
18 inches (457 mm) from the wall at the back, only for models approved for this reduced clearance. This reduction never applies to the distance from a window, a door or an air intake;
5 feet (1.52 m) above;
never under a wooden deck.

For windows, doors and air intakes, Generac refers to local codes. It also states that a well-placed generator can still let carbon monoxide in under certain conditions, and recommends a carbon monoxide alarm on every floor. A smoke alarm doesn’t detect this gas.

The municipality also has its say. In Longueuil, for example, no permit is required for a residential generator, but the city requires a distance of 2 m from the property line, a side or back yard, a sound-attenuating enclosure and a screen. Each city has its rules: check with yours before choosing the location.

Who does what

The electrical part: an electrical contractor who is a member of the CMEQ. Hydro-Québec points it out: installing a generator must be done by a master electrician. The Code requires an approved transfer switch with a capacity at least equal to the load. The contractor then declares the work to the Régie du bâtiment.

The gas part: a gas contractor holding the appropriate licence from the Régie du bâtiment (natural gas or propane). We don’t do this part: it belongs to a licensed gas contractor. We do all the electrical part.

The equipment: in Québec, the engine of a generator connected to gas must be approved, and so must the switch.

Propane or natural gas

On natural gas, the generator is supplied continuously by the network, with no tank to fill. Your address still has to be served: check with your natural gas distributor (Énergir, for example). On propane, you need a tank: Generac requires at least 250 US gallons for a residential generator. Cylinders aren’t enough.

What the propane models use, according to Generac’s spec sheets:

Model	At half load	At full load
14 kW	6.87 L/h	11.61 L/h
18 kW	6.45 L/h	11.44 L/h
22 kW	9.57 L/h	14.77 L/h
24 kW	9.57 L/h	14.77 L/h
26 kW	7.78 L/h	13.73 L/h

How long it runs depends on the size of the tank and on what the house uses during the outage: your propane supplier can calculate it with you. To compare fuels in detail, see our guide on the propane or dual fuel generator.

Maintenance in Québec

What	When
Automatic test (the generator starts on its own, without taking the house)	5 minutes every two weeks by default, adjustable to weekly or monthly
First oil and filter change	After the first 25 hours (break-in)
Oil and filter change, in cold weather (below 4.4 °C)	Every year or every 100 hours
Oil and filter change, above 4.4 °C (not the case in a Québec winter)	Every two years or every 200 hours

Generac’s standard warranty is 5 years or 2,000 hours, but it decreases over time: parts, labour and travel the first two years, parts only the third, engine and alternator only the fourth and fifth. Generac offers extended warranties of 5, 7 or 10 years. In every case, you must be able to prove that the required maintenance was done.

Frequently asked questions

How much does it cost to install an automatic generator?

At STM-Électrique, the price of the installed automatic transfer switch is in the written quote, free of charge. The generator is extra, depending on its size, as are the gas connection and the pad. We give you the price of the electrical part in writing after seeing the installation. The gas part is priced by the gas contractor.

What size generator for my house?

It depends on what you want to keep running, not just on the floor area. A load calculation determines it. With load management certified for Canada, a smaller generator can back up the whole house by temporarily shutting off large appliances.

Is a permit needed?

It depends on the municipality. Longueuil, for example, doesn’t require one for a residential generator, but imposes distances and a screen. Check with your city. On the electrical side, the contractor declares the work to the Régie du bâtiment.

Does it start if I’m not home?

Yes, that’s the whole point: the automatic switch detects the outage, starts the generator and switches the house over on its own, then goes back to the grid when the power returns.

How much propane does it use?

According to Generac’s spec sheets, a 22 kW model uses about 9.57 litres per hour at half load and 14.77 litres at full load. You need a tank of at least 250 US gallons. Your propane supplier can estimate how long it runs based on your tank.

Is it noisy?

According to Generac, for the 10 to 24 kW models, 61 to 67 dB(A) at 7 metres in normal operation, depending on the model, and 55 to 57 dB(A) during the automatic test in quiet mode.

What is the warranty?

Generac’s standard warranty is 5 years or 2,000 hours, with coverage that decreases after the second year. Extended warranties of 5, 7 or 10 years exist. The maintenance must be done and proven for the warranty to apply.

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Sources

The figures and requirements cited in this guide come from the documents below, consulted on October 4, 2026. Manufacturers’ spec sheets change: check the current version before committing to any expense.