What size generator do I need for my Calgary home during a winter power outage?

The right generator size for your Calgary home depends on what you need to keep running during an outage, but most homes need between 16kW and 22kW for whole-home standby coverage, or 5,000 to 7,500 watts if you are using a portable generator to power only the essentials. Your licensed electrician will perform a detailed load calculation to determine the exact size, but understanding the basics helps you plan and budget.

The single most critical load in a Calgary winter outage is your furnace. Even a high-efficiency gas furnace requires electricity to run the blower motor, igniter, and control board — typically drawing 500 to 800 watts running, with a startup surge of 1,500 to 2,500 watts. Without the furnace, indoor temperatures in a well-insulated Calgary home can drop below freezing within 8 to 12 hours when it is -30 outside, and pipes can begin to freeze within 24 hours. Beyond the furnace, your priority loads typically include the refrigerator (150 to 400 watts running), freezer (100 to 300 watts), sump pump if applicable (800 to 1,500 watts startup), basic lighting (200 to 500 watts), garage door opener (500 to 700 watts), and a few outlets for charging devices and communication.

For a portable generator strategy, a quality 5,000 to 7,500 watt unit costing $1,200 to $2,500 can handle the furnace, fridge, freezer, sump pump, and some lighting — but you will need to manage loads carefully and avoid running everything simultaneously. The startup surge of motors is the key constraint; a sump pump and furnace starting at the same moment can overload a smaller portable unit. A manual transfer switch or interlock kit ($1,200 to $2,200 installed) is the safe, code-compliant way to connect a portable generator to your home's panel.

For whole-home standby generators, Calgary electricians typically recommend a 16kW unit for homes under 2,000 square feet with standard electrical loads, and a 22kW unit for larger homes or homes with higher demands such as electric ranges, hot tubs, EV chargers, or multiple heating zones. A 16kW generator produces enough power to run the furnace, all lighting, kitchen appliances, entertainment systems, and home office equipment simultaneously. A 22kW unit can handle virtually everything in the home without load management.

Calgary's extreme cold introduces considerations that do not apply in milder climates. Engine block heaters draw 400 to 1,000 watts and are essential for vehicles parked outdoors, so factor these into your load calculation if you need your vehicles to start during a prolonged outage. Space heaters, which many homeowners use as supplemental heat, draw a hefty 1,500 watts each on a dedicated circuit — adding even two of these substantially increases your required generator capacity. If you have a heat pump as your primary heating source, the compressor and auxiliary heating elements can draw 3,000 to 8,000 watts, which pushes you firmly into the 22kW category.

Your electrician's load calculation will account for all of these factors plus the demand factor — the realistic expectation of what runs simultaneously versus what runs intermittently. The Alberta Building Code and Canadian Electrical Code provide specific guidance on load calculations, and your electrician will use these standards to recommend a properly sized unit. Oversizing slightly is generally better than undersizing, as running a generator at 50 to 75 percent capacity is more efficient and extends the unit's lifespan compared to running at full load continuously. Get matched with a licensed Calgary electrician who can perform a proper load calculation through the Calgary Construction Network directory.