How many solar panels do I need?

Quick answer: A typical Ontario home uses about 9,000 kWh of electricity a year, and each kilowatt of south-facing panels in Toronto makes about 1,163 kWh a year, so most homes need about 8 kW of solar: 16 panels at 500 W. Divide your yearly kWh by your area’s yield, then double the kW for 500 W panels.

Key takeaways

• Start with your bill: find your yearly use in kWh. Our home solar panels page covers what an install includes.
• The Ontario Energy Board’s typical household uses 750 kWh a month, or 9,000 kWh a year.
• Location matters: Natural Resources Canada estimates 1,163 kWh per kW a year in Toronto and 1,200 in Ottawa for a south-facing array.
• With 500 W panels, the panel count is the system size in kW times 2: 5 kW is 10 panels, 8 kW is 16, 10 kW is 20.
• In Ontario, net metering credits expire after 12 months, and the Home Renovation Savings rebate rules out net metering, so oversizing does not pay.

One of the first questions that need to be answered if you are going solar is exactly how
many panels you need to buy. The answer isn’t one-size-fits-all because the number of
solar panels required depends on several factors unique to your home and lifestyle. Too
few panels would mean you aren’t covering enough of your power bill for it to be of value;
too many panels means that you might be overpaying since most provinces don’t let you
liquidate your Net Metering credits as cash. There is a sweet spot where you are producing
just enough energy and excess credits to cover your bill over a 365-day period. In Ontario, net metering credits carry forward for up to 12 months and then expire (O. Reg. 541/05). The solar panel calculator gives a quick estimate from your bill.

What factors influence your system size?

Let’s look through some of the factors that influence your system size, and don’t be
overwhelmed, we will build a solar proposal for you based on all of these factors.

1. Roof Space: The amount of available roof space can limit the number of panels you
   can install. If space is limited, higher-wattage panels make more power from the same area; Xolar installs 500 W panels. You may also see “Tier 1” in solar marketing: it is BloombergNEF’s list of makers whose panels went into bank-financed projects, a measure of bankability, not of panel quality or wattage.
2. Roof Orientation: Since Canada is in the northern hemisphere of the Earth, we get
   all our most direct sunlight from the South. If your roof is facing south then you
   have an optimal property for solar. This doesn’t rule out east/west facing roofs
   though, you can design systems where your east facing panels capture the early day
   sunlight and the west captures the sunlight of the afternoon. Pitch matters less than direction: Natural Resources Canada’s Toronto figures are 1,174 kWh per kW a year at a tilt 15 degrees flatter than latitude, 1,163 at latitude tilt, and 802 for panels mounted vertically.
3. Sunlight Exposure: Roof Space and Roof orientation directly affect sunlight
   exposure but also some provinces tend to get more direct sunlight than others. The
   amount of sunlight your location receives directly affects your solar system’s
   output. Areas with more sunlight require fewer panels to generate the same amount of electricity. For example, Natural Resources Canada puts Ottawa at 1,200 kWh per kW a year, slightly above Toronto’s 1,163.
4. Assess Your Yearly Energy Consumption: Your electricity bill is a good source of information, look for the section that shows your yearly consumption in kilowatt-
   hours (kWh). This figure represents the total amount of electricity your household uses over the course of a year, taking into account seasonal fluctuations. The Ontario Energy Board defines a typical Ontario household as using 750 kWh a month, or 9,000 kWh a year.
5. Future Energy Needs: Consider whether your energy needs might increase in the
   future. For example, if you’re planning to add an electric vehicle (EV) or expand your
   home, you might want to install additional panels now to accommodate higher
   energy consumption later.

Understanding Solar Panel Output

The output of a solar panel is measured in watts, and panels come in a range of sizes. Xolar installs 500 W panels, so two panels make 1 kW of capacity. A panel’s yearly energy is its capacity multiplied by the yield for your location, which already accounts for the hours of usable sun and typical system losses.

For instance, Natural Resources Canada’s estimate for a south-facing array in Toronto is 1,163 kWh per kW per year, after typical system losses. A 500 W panel there would make about 580 kWh a year, or about 1.6 kWh a day on average, with much more in July than in December. Not every roof faces south, so our proposals use your roof’s actual direction, tilt and shading.

Calculating the Number of Panels

To determine the number of panels you need, divide your average monthly electricity consumption by the average monthly output of one panel. Of course, this is also impacted by factors listed above like your roof orientation and pitch, sunlight exposure, and future energy needs. We do all the calculations of the other factors for you. Worked example: 9,000 kWh a year divided by 1,163 kWh per kW is about 7.7 kW, which rounds to an 8 kW system of 16 panels at 500 W. That system would make about 9,300 kWh a year in Toronto. A home using 12,000 kWh a year would need about 10 kW, or 20 panels.

Upsizing Your Solar System

One of the advantages of solar energy is the ability to upsize your system over time. If your energy needs increase, you can add more panels to your existing system, provided you have the roof space and your inverter can handle the additional capacity. Our comparison of string and micro inverters explains how each type handles expansion. Upsizing allows you to start with a system that meets your current needs while keeping the option open for future expansion.

Frequently asked questions

How many solar panels do I need to power a house?

Divide your yearly use in kWh by your location’s yield per kW, then convert to panels. A typical Ontario home uses 9,000 kWh a year; at Toronto’s 1,163 kWh per kW, that is about 7.7 kW, or 16 panels at 500 W. Homes with electric heat, a heat pump or an electric vehicle often use more and may need 20 panels or more.

How many kW of solar do I need?

Take your yearly kWh and divide it by your area’s yield: about 1,163 kWh per kW in Toronto and 1,200 in Ottawa, based on Natural Resources Canada’s figures. In Toronto, 6,000 kWh a year needs about 5 kW, 9,000 kWh about 8 kW, and 12,000 kWh about 10 kW. Shade and east- or west-facing roofs lower the yield, so the system gets a little bigger.