Formulas & Calculations
📊 Note on system losses:
Real-world solar output is typically 15–25% lower than theoretical calculations due to inverter losses, wiring resistance, temperature derating, and soiling. For system sizing purposes, multiply your calculated output by 0.80 to get a realistic estimate. Peak sun hours sourced from NRCan solar radiation data.
Solar Panel kWh Output Reference — Canada
Daily kWh output per panel by wattage and province (before system losses).
| Panel Size |
Alberta (4.8h) |
Saskatchewan (4.5h) |
BC / Ontario (4.0h) |
Quebec (3.8h) |
Nova Scotia (3.5h) |
| 100W | 0.48 kWh | 0.45 kWh | 0.40 kWh | 0.38 kWh | 0.35 kWh |
| 200W | 0.96 kWh | 0.90 kWh | 0.80 kWh | 0.76 kWh | 0.70 kWh |
| 300W | 1.44 kWh | 1.35 kWh | 1.20 kWh | 1.14 kWh | 1.05 kWh |
| 400W | 1.92 kWh | 1.80 kWh | 1.60 kWh | 1.52 kWh | 1.40 kWh |
| 500W | 2.40 kWh | 2.25 kWh | 2.00 kWh | 1.90 kWh | 1.75 kWh |
* Multiply by number of panels and 30 for monthly output. Reduce by 20% for real-world system losses.
Frequently Asked Questions
How many kWh does a 400W solar panel produce per day?
A 400W panel produces 1.6 kWh/day in Ontario (4.0 peak sun hours), 1.92 kWh/day in Alberta (4.8h), and 1.40 kWh/day in Nova Scotia (3.5h). Multiply by your number of panels for total array output, then reduce by 20% for real-world system losses.
What is the difference between watts and kilowatt-hours?
Watts (W) measure power — the rate of energy at a single moment. Kilowatt-hours (kWh) measure energy — the total amount used or produced over time. Think of watts like a speedometer (speed right now) and kWh like an odometer (total distance travelled). Your electricity bill charges you for kWh, not watts.
How do I convert kWh back to watts?
Watts = (kWh × 1,000) ÷ Hours. For example, if an appliance used 2.4 kWh over 8 hours: (2.4 × 1,000) ÷ 8 = 300W. This is useful for figuring out the wattage of an unlabelled device from your electricity bill.
How many solar panels do I need to produce 30 kWh per day?
With 400W panels in Ontario (4.0 peak sun hours), each panel produces 1.6 kWh/day before losses, or about 1.28 kWh/day after 20% system losses. To produce 30 kWh/day you'd need roughly 24 panels. Use our
solar panel calculator for a full estimate based on your location and usage.
Why is my actual solar output lower than calculated?
Real-world output is typically 15–25% lower than theoretical calculations due to: inverter efficiency losses (5–10%), wiring resistance (1–3%), temperature derating on hot days (5–10%), panel soiling/dust (2–5%), and suboptimal tilt or shading. Always apply a 20% derating factor to calculated output for realistic system sizing.