FindSolar.caThe number of panels your home needs has almost nothing to do with the size of the house and everything to do with how much electricity it uses. Two identical bungalows on the same street can need systems half or double each other's size, because one heats with gas and the other runs a heat pump, a hot tub and two EVs. So skip the square footage and start where the professionals start: your last 12 months of power bills.
The sizing math, in one paragraph
Take your annual usage in kilowatt-hours, decide what share of it you want solar to cover, and divide by what one installed kilowatt of panels produces per year where you live, a figure that runs from about 950 to 1,300 kWh per kW across Canada on planning averages. A home using 10,000 kWh a year aiming for full coverage in a 1,150 kWh-per-kW region needs roughly 8.7 kW. At today's typical 400 to 500 watt residential panels, that is about 18 to 22 panels. Our savings calculator does this from your monthly bill and can swap in satellite data for your exact location.
Panels per system size
| System size | Panels (400 to 500 W) | Roof area, planning figure |
|---|---|---|
| 5 kW | 10 to 13 | roughly 500 sq ft |
| 8 kW | 16 to 20 | roughly 800 sq ft |
| 10 kW | 20 to 25 | roughly 1,000 sq ft |
| 15 kW | 30 to 38 | roughly 1,500 sq ft |
Planning figures at about 100 sq ft per kW of unshaded roof. Real layouts lose space to vents, setbacks and roof shape.
Why 100% coverage is not always the target
Where net metering credits full retail value, sizing to your whole usage is reasonable. Where exports earn less than retail, or credits expire annually, the last panels you add earn the least, and a system covering 70 to 90% of usage can return more per dollar than one covering everything. This is province-specific; our sizing guide covers when bigger stops being better, and the net metering guide shows what your province pays.
Size for the house you are about to have
An EV adds roughly 2,500 to 4,500 kWh a year on planning figures; a heat pump can add more. If either is in your two-year plan, tell the designer now, because panel space you leave unused is cheap to wire for and expensive to retrofit. The reverse also holds: if the teenagers and their showers are leaving, your future usage may be smaller than your last 12 months suggest.
Questions homeowners ask
How do I calculate how many solar panels my house needs?
Annual kWh usage, times the share you want covered, divided by your region's production per installed kW (roughly 950 to 1,300 kWh per kW across Canada on planning averages), gives system size in kW. Divide by panel wattage, typically 400 to 500 W, for the panel count. Our calculator does it from your monthly bill.
Can I size solar based on the square footage of my house?
No. House size predicts almost nothing about electricity use; heating fuel, EVs, pools and habits do. Two identical homes can need systems double or half each other's size. The only reliable input is your own metered usage over 12 months.
Should I size my system to cover 100% of my electricity use?
Only where your province credits exports at or near retail rates. Where export credit is lower, or banked credits expire, the last panels earn the least, and 70 to 90% coverage often returns more per dollar. Check your province's rules before settling on the target.
How many panels would a 5 kW, 10 kW or 15 kW system use?
With modern 400 to 500 watt residential panels: about 10 to 13 for 5 kW, 20 to 25 for 10 kW, and 30 to 38 for 15 kW. Roof layout, vents and setback rules decide how many actually fit, which is why designers work from satellite imagery and a site visit.
Should I include a future EV or heat pump when sizing solar?
If it arrives within a couple of years, yes: an EV adds roughly 2,500 to 4,500 kWh a year on planning figures, and a heat pump can add more. Designers can size the inverter and wiring for expansion even if you start smaller, but only if you tell them now.
What happens if my roof cannot fit the system size I need?
You still have options: higher-wattage panels, a second roof face at a modest production discount, a ground mount if you have the land, or accepting partial coverage, which still offsets your most expensive power. Cutting usage first, through efficiency, shrinks the system you need at all.