FindSolar.caEvery solar quote stands on one estimate: how many kilowatt-hours the system will produce in a year at your address. Price is printed in ink, but production is a forecast, and it is the number that turns installed kilowatts into actual dollars. Understanding what drives it lets you sanity-check any claim in minutes.
From kW on the roof to kWh on the meter
Panels are rated in kilowatts of capacity; your house runs on kilowatt-hours of energy. The bridge between them is your location's solar resource. Across Canada, one installed kW of well-oriented panels yields roughly 950 to 1,300 kWh a year on planning figures, with the Prairies at the top of the range and coastal and northern regions lower. A 10 kW system therefore lands roughly between 9,500 and 13,000 kWh a year depending on where it sits, before site-specific adjustments.
What your roof does to the number
| Orientation | Share of ideal production, planning factor |
|---|---|
| South | 100% |
| Southeast or southwest | about 96% |
| East or west | about 85% |
| North | about 62% |
Planning factors used by our calculator; pitch and local horizon shift them modestly.
Shade is the wildcard. A chimney's afternoon shadow or a spruce that clears the roofline in August is invisible in averages and can cost real production. It is site-specific enough that it should be modelled with proper tools during design, not guessed at from the driveway.
Clouds, snow and the weather already in the math
Panels produce on cloudy days at reduced output, not zero, and December in most of Canada delivers a small fraction of July. None of this should surprise the estimate, because honest production figures are built from decades of local weather data, snow and all. That is why a system in Calgary and a system in St. John's carry different annual numbers for identical hardware, and why winter performance is a shape of the curve, not a flaw in it.
Checking a claim, and then checking the reality
Before signing: divide the quote's annual kWh by its kW and compare the result against an independent benchmark for your location, either NRCan's photovoltaic potential maps or the satellite mode in our savings calculator, which pulls European Commission PVGIS data for your coordinates. Our step-by-step verification guide shows the whole routine. After commissioning: your inverter's monitoring app reports actual production; compare full years rather than single months, because weather noise washes out at twelve months.
Questions homeowners ask
How many kWh will a 10 kW solar system produce in my city?
On planning figures, roughly 9,500 to 13,000 kWh a year depending on region, with Prairie cities at the top of the range. Your roof's orientation and shade adjust it from there. The satellite mode in our calculator gives a location-specific figure from open PVGIS data in seconds.
Does a south-facing roof produce much more than east or west?
South produces the most annually; east or west gives up roughly 15% on planning factors, which is real but rarely fatal to the math. West-facing panels also shift production toward late afternoon, which can be worth more where you use more power in the evening or where export credit is low.
How much production do I lose from shade?
Anywhere from almost nothing to enough to kill the project, which is why nobody should guess. Shade is the most site-specific input in the estimate: a designer should model your actual obstructions with proper tools, and the quote should state its shading assumption so you can see it.
Do solar panels produce anything on cloudy or snowy days?
Yes on cloudy days, at reduced output rather than zero. Snow-covered panels produce little until they shed, which tilted panels do surprisingly fast in sun. Honest annual estimates are built from decades of local weather, so clouds and snow are already inside the number, not surprises waiting to reduce it.
Why does the installer's estimate differ from an online calculator?
Different weather datasets, loss assumptions, and above all shade modelling: a good installer models your actual roof, which a generic calculator cannot. Small gaps are normal. What deserves a question is an installer figure far above the independent benchmarks for your location, because errors that direction are rarely accidents.
How can I track whether my system is producing what I was promised?
Use the inverter's monitoring app, which every modern system includes, and compare full-year actuals against the quote's annual estimate. Judge years, not weeks: a cloudy month means nothing. A persistent shortfall across a year is exactly what the production estimate and workmanship warranty conversations were for.