Ask most homeowners what they want from a standby generator and the answer is simple: when the power goes out, I want my house to work. The harder question is what "work" means, because the answer determines the size of generator you need, and sizing is where most generator decisions go sideways.
Wattage charts and online calculators exist everywhere, but they rarely translate into what daily life looks like during an outage in a real Toronto-area home. So instead of abstract numbers, let's walk through what different Generac sizes actually run in a typical GTA detached house, and how a proper sizing assessment works.
Here's the shortcut to understanding generator sizing: air conditioning is the fork in the road.
Most of a home's essentials are modest, steady loads. A fridge, a freezer, the furnace fan, lights, internet, phone charging, and critically for GTA homeowners, the sump pump. All of that together fits comfortably within a smaller standby unit.
Central air conditioning is different. The compressor draws a large amount of power, and it demands a surge of extra current every time it starts. Whether you want AC running during an outage is the single biggest factor in what size Generac your home needs. Everything else is detail by comparison.
Generator models change over time, so think in tiers rather than exact model numbers.
The essentials tier (smaller standby units, roughly 10kW class). This covers what keeps your home safe and livable: sump pump, fridge and freezer, furnace (the fan and controls, since gas heat needs surprisingly little electricity), lights, internet, and a selection of outlets. During a summer outage the house gets warm, but the basement stays dry and the food stays cold. For many homes, especially those with modest square footage, this tier covers what genuinely matters.
The comfort tier (mid-size units, roughly 18 to 22kW class). This is the most popular choice in the GTA for a reason: it runs the essentials plus central air conditioning in most homes, along with the majority of everyday circuits. Life continues more or less normally. Laundry might wait, and you wouldn't run the oven, the dryer, and the AC simultaneously, but you wouldn't often want to anyway.
The whole home tier (larger units, 24kW and up). Everything runs, no thinking required. Larger homes, homes with two AC units, heated garages, pools, or extensive electrical loads land here. So do households that simply don't want to manage anything during an outage.
Here's what most homeowners don't know: load management can make a mid-size generator behave like a bigger one.
Generac's load management modules watch what the generator is supplying in real time. When capacity runs tight, they briefly shed lower-priority loads, pausing the AC compressor or the dryer for a few minutes, then restoring them when room opens up. In practice, this means a well-configured 18kW system with load management often delivers what looks like whole-home coverage, because a household rarely uses everything at once.
This is also why generator sizing isn't really a wattage math exercise. It's a design decision about priorities, and it's where an experienced installer earns their fee.
A legitimate assessment starts at your electrical panel, not a sales brochure. A licensed electrician will look at your actual connected loads, identify the motor loads that create starting surges (AC, sump pump, well pump if you have one), ask how you actually live, and account for what's coming. Planning an EV charger? Converting to a heat pump? Finishing the basement? Sizing for the home you'll have in five years costs little extra now and avoids a painful undersizing discovery later.
Be wary of anyone who quotes you a generator size over the phone based on square footage. Two identical-footprint homes can need completely different systems.
Most GTA installations run on natural gas, which means no fuel storage and no refueling during an extended outage. Your gas meter and supply line need to be verified for the added demand, since larger generators sometimes require a meter or line upgrade. That's part of a proper installation assessment and one more reason sizing decisions involve more than the nameplate wattage.
Match the generator to how you actually live: essentials-only for security and peace of mind, mid-size with load management for near-normal living, or whole-home for zero compromises. The right answer depends on your panel, your loads, and your priorities, and it starts with a proper in-home assessment.
Murtex Electric provides generator sizing assessments and Generac installations for homeowners across Toronto, Etobicoke, North York, Vaughan, Markham, Richmond Hill, Mississauga, Burlington, Oakville, and Caledon. If you're considering standby power, contact us for an honest assessment of what your home really needs.
