Solar Panels kWh Calculator

How to use this calculator

This tool sizes a solar system from the kWh number on your hydro bill — the opposite direction of a production calculator. Enter six values and it returns required system size in kW, panel count, daily/monthly/annual production, offset achieved, and year-1 bill savings:

1. Monthly electricity use (kWh) — average from your last 12 months of bills. StatCan 2026 Canadian average is 938 kWh/month (11,255 kWh/year).
2. Target offset (%) — how much of your bill you want to eliminate. 85–100% is standard depending on net metering policy.
3. Peak sun hours per day — Canadian average is 3.8. NRCan PV Potential tool shows exact values: Calgary 4.4, Regina 4.3, Winnipeg 4.0, Toronto 3.7, Ottawa 3.8, Montreal 3.7, Halifax 3.6, Vancouver 3.2.
4. System efficiency (%) — leave at 76% (Canadian default with 2–4% snow loss baked in). Use 78% if your array tilt is 35°+ for fast snow shed.
5. Panel wattage (W) — STC nameplate. 2026 Canadian standard is 400–460 W (Silfab, Canadian Solar, Q CELLS).
6. Electricity rate (C$/kWh) — your blended residential retail rate. Provincial averages 2026: AB 18c, ON 13.6c (TOU midpoint), QC 7.8c, BC 11.5c, NS 17c, SK 18c, MB 11c, NB 13c.

The formula

annual_need_kWh   = monthly_kWh × 12
target_kWh        = annual_need_kWh × (offset / 100)
required_array_W  = target_kWh × 1000 / (PSH × 365 × derate)
panel_count       = ceil(required_array_W / panel_W)
actual_array_W    = panel_count × panel_W
daily_production  = actual_array_W × PSH × derate / 1000
year1_savings     = min(annual_production, annual_need) × rate

The savings figure assumes self-consumption — every kWh you produce displaces a kWh from the grid at retail rates.

A worked example for the Canadian average household at 85% offset:

• Need: 938 × 12 = 11,256 kWh per year
• Target: 11,256 × 0.85 = 9,568 kWh
• Required array: 9,568 × 1000 / (3.8 × 365 × 0.76) = 9,067 W
• Panel count: ceil(9067 / 400) = 23 panels
• Actual array: 23 × 400 = 9,200 W (9.2 kW)
• Daily production: 9200 × 3.8 × 0.76 / 1000 = 26.6 kWh
• Annual production: 26.6 × 365 = 9,696 kWh (86% offset)
• Year-1 savings at C$0.16/kWh: C$1,551

System size by household consumption

Using 3.8 peak sun hours, 76% derate, 400 W panels, 85% target offset:

*At C$0.16/kWh blended residential rate. Provincial rates vary widely.

What changes the result

Peak sun hours by city

NRCan 2026 PV Potential confirms:

• 7.7 kW in Calgary at 4.4 PSH (20 panels)
• 7.9 kW in Regina at 4.3 PSH (20 panels)
• 8.5 kW in Winnipeg at 4.0 PSH (22 panels)
• 9.2 kW in Ottawa at 3.8 PSH (23 panels)
• 9.4 kW in Montreal at 3.7 PSH (24 panels)
• 9.4 kW in Toronto at 3.7 PSH (24 panels)
• 9.7 kW in Halifax at 3.6 PSH (25 panels)
• 10.9 kW in Vancouver at 3.2 PSH (28 panels)

Same 11,256 kWh/year household, same 85% target offset. Calgary and the prairies enjoy materially better solar economics than coastal BC despite the cold — peak sun hours dominate.

Provincial net metering and incentives

Net metering rules vary substantially:

• Alberta: Solar Club + Micro-generation 1:1 retail credit, $5,000 federal Greener Homes Grant ended Mar 2024 but Greener Homes Loan continues at 0% interest up to $40k.
• Ontario: 1:1 net metering, no provincial incentive. Ottawa City Better Homes loan 0% up to $40k.
• Quebec: Hydro-Québec net metering 1:1 with annual reset 31 March (any unused credit forfeited). Rénoclimat $1,000 for new install.
• BC: BC Hydro net metering 1:1 with no expiry on credits. Greener Homes Loan applies.
• Saskatchewan: SaskPower Net Metering 2.0 — 7.5c/kWh export only, no 1:1. Aim for 70–80% offset to maximise self-consumption.
• Manitoba: Manitoba Hydro Solar Energy Program net metering 1:1.
• Atlantic provinces: NS SolarHomes Rebate $0.30/W up to $3k. NB Total Home Energy Savings Program $5k. PEI Solar Electric Rebate $1.00/W up to $10k. NL Energy Efficiency loan.

Panel orientation and tilt

The reference case is south-facing at 35–45° tilt (matches Canadian latitudes and sheds snow). Off-axis penalties (NRCan PVAvailability):

• East or west: 12–18% loss versus south
• North: 30–45% loss (avoid)
• Flat (0° tilt): 10–15% loss + much higher snow accumulation
• Steep (60°+ tilt): 5–8% loss but excellent snow shed in Quebec/Newfoundland

CSA C22.1 Section 64-216 requires structural review for snow loads — high-tilt arrays in heavy-snow regions still need snow load engineering for the racking.

Snow and winter loss

Snow losses (CanmetENERGY 2026 fleet data):

• Vancouver, lower mainland BC: 1–2% annual
• Toronto, Hamilton: 2–4%
• Ottawa, Montreal: 4–6%
• Calgary, Edmonton: 3–5% (drier snow, sheds faster)
• Quebec interior, Atlantic Canada: 6–10%

A 35°+ tilt sheds snow within hours on a sunny day; flat arrays can sit covered for weeks. The winter performance research from CanmetENERGY’s Varennes test facility is the authoritative Canadian source.

Why size from kWh, not from roof space

Roof-area sizing is the planning-stage shortcut. kWh sizing is what eliminates a bill. NRCan’s 2026 Residential Solar Sizing Guide confirms: kWh-driven sizing is the standard for any CSA-compliant install.

The right workflow:

1. Sum 12 months of bills. Add projected load if you are buying an EV (4,000–5,500 kWh/yr at 20,000 km, accounting for cold-weather efficiency drop) or air-source heat pump (4,000–8,000 kWh/yr replacing gas, NRCan ASHP database).
2. Decide your offset target. Net metering 1:1 provinces: 95–105%. SaskPower-style: 75–85%.
3. Run this calculator with local PSH from NRCan’s PV Potential tool.
4. Sanity-check roof area: each 400 W panel needs ~22 sq ft. A 9 kW system needs ~500 sq ft of unshaded south-facing roof.
5. Get quotes from CSA-accredited installers — required for permitting and Greener Homes Loan eligibility.

Common mistakes

• Using US PSH for Canadian installs: NREL PVWatts gives Toronto 4.1 PSH, but Canadian field data from CanmetENERGY consistently shows 3.7 — a 10% gap that underbuilds systems.
• Ignoring snow shedding: A flat-tilted array in Quebec has substantially worse winter output than the math implies; tilt matters more in Canada than in California.
• Sizing for January: Canadian December–February output is 10–20% of June. Solar is annualised — you bank summer surplus, but Quebec’s annual reset means you need to consume credits before March 31 each year.
• Forgetting Class A meter requirements: All CSA-compliant net metering installs need a bidirectional Class A meter (typically supplied free by utility) and ESA (Ontario) / Technical Safety BC (BC) inspection — factor 2–6 weeks of permit time into project planning.

Sources

• NRCan PV Availability and Photovoltaic Potential Maps — peak sun hours for any Canadian location
• CanmetENERGY — Varennes test facility data on snow losses, derate factors
• StatCan CANSIM 25-10-0021-01 — Canadian residential electricity consumption benchmarks
• Solar Industry Magazine 2026 Canada Report — installer pricing and provincial breakdown
• CSA C22.1 Canadian Electrical Code — Canadian installation and safety requirements (Section 64)
• Canadian Renewable Energy Association (CanREA) — provincial policy tracker