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Solar Greenhouse Calculator

Calculate the PV system size and annual energy to run a heated Canadian greenhouse. Free calculator with NRCan-grade U-values and Greener Homes payback.

Solar Greenhouse Calculator

Heating load (thermal)
86,400 kWh
Heating electricity
34,560 kWh
Lighting electricity
9,450 kWh
Fans + circulation
500 kWh
Total electricity / year
44,510 kWh
Annual electricity bill
$6,231
Recommended PV size
39.1 kW
PV installed cost
$89,896
Simple payback (years)
14.4

How this calculator works

A Canadian greenhouse has three big electric loads: space heating (the dominant cost north of the 49th parallel), supplemental lighting (essential for any winter cropping at 45°N+), and ventilation. Enter ten values and the calculator returns annual kWh per load, PV size required, installed cost, and simple payback.

  1. Greenhouse floor area in m² — heated footprint only.
  2. Glazing material — single polyethylene, double-polyethylene inflated, twin-wall polycarbonate, or double-glazed glass. U-values per CSA standard and NRCan EnergyStar data.
  3. Climate zone — cold (Winnipeg, Edmonton), moderate (Toronto, Montréal), or mild (Vancouver, Victoria). Tropical does not apply to Canada.
  4. Heating COP — 1.0 for resistance, 2.5–3.0 for a cold-climate air-source heat pump averaged across the Canadian heating season per CanmetENERGY field trials, or 0 to skip heating from the PV calculation if you burn propane or fuel oil.
  5. Supplemental lighting W/m² — 80–120 W/m² for leafy greens at 45°N+, 150–250 W/m² for fruiting crops.
  6. Lighting hours per day — 4–6 hours of supplemental light extension through November–March.
  7. Lighting active days per year — typically 180–220 days through the heating season.
  8. Electricity rate in C$/kWh — Hydro-Québec D-rate is C$0.077/kWh, Manitoba Hydro C$0.10/kWh, Ontario tiered C$0.14/kWh, BC Hydro Step 2 C$0.16/kWh, Maritime utilities C$0.16–C$0.18/kWh.
  9. Peak sun hours per day — 3.5 in Vancouver, 4.0 in Toronto and Ottawa, 4.4 in Calgary, 4.6 in Edmonton, 5.0 in Saskatoon, 4.2 in Halifax (NRCan PV Atlas).
  10. PV installed cost per kW — NRCan median for residential 5–15 kW PV installs in 2026 is C$2,200–C$2,500/kW after PST/HST exemptions.

The maths is first-principles: thermal load = U × envelope_area × HDD × 24 / 1000. We assume the greenhouse envelope is 2× the floor area. Lighting kWh = (W/m² × m²) / 1000 × hours × days. Fan and circulation load is fixed at 5 kWh/m²/year per CanmetENERGY St-Bruno monitored data.

Why solar is suddenly viable for Canadian greenhouses

Before 2022 almost no Canadian greenhouse used solar — winter sun is weak, heat loads are huge, and natural gas at C$0.04/kWh-equivalent was unbeatable. Three things changed.

First, cold-climate ASHPs hit COP 2.0 at −25°C, validated by CanmetENERGY’s Varennes lab and the Ontario Cold Climate Heat Pump Project. That brings heat-pump-delivered heat to about C$0.04–C$0.06/kWh thermal — competitive with gas after carbon pricing.

Second, the federal Greener Homes Loan offers up to C$40,000 at 0 percent interest for retrofits including PV, batteries, and heat pumps. The Greener Homes Grant adds up to C$5,000 toward ASHP installs.

Third, NRCan-installed PV cost dropped from C$3,800/kW in 2018 to C$2,200–C$2,500/kW in 2026, and provincial net-metering programs (Hydro-Québec, SaskPower, BC Hydro, Manitoba Hydro, Nova Scotia Power, NB Power) credit exported kWh at retail rate.

The combined effect is that a fully-electrified PV + ASHP greenhouse now pencils at a 10–14 year payback in Ontario and Quebec, 8–12 years in the Maritimes (high retail rates), and 12–15 years on the Prairies (lower retail rates offset by higher solar yield).

Glazing U-values for Canadian conditions

Canadian greenhouse glazing must survive snow loading per NBCC 2020 Climate Data, hail per ASCE 7 ULS, and freeze-thaw cycling. Practical U-values from CSA C22.1 and the Canadian Greenhouse Conference:

  • Single polyethylene (6 mil) — U = 6.0 W/m²·K, 2–3 year life in Canadian UV + cold, C$8–C$12/m². Acceptable for season-extension hoop houses only.
  • Double polyethylene inflated — U = 4.0 W/m²·K, 4–5 year life, C$18–C$28/m². The dominant choice for Canadian commercial greenhouses.
  • Twin-wall polycarbonate — U = 3.5 W/m²·K, 12–15 year life, C$55–C$85/m². Best for hobby and small commercial year-round operation.
  • Double-glazed glass — U = 2.8 W/m²·K, 25+ year life, C$220–C$340/m². Only justified for high-value crops in Greenhouse Belt operations (Leamington, Delta).

A 100 m² double-poly greenhouse with 2× envelope = 200 m². In Toronto (HDD18 ≈ 4000 K·day):

  • Double polyethylene: 4.0 × 200 × 4000 × 24 / 1000 = 76,800 kWh thermal/yr
  • Twin-wall polycarbonate: 3.5 × 200 × 4000 × 24 / 1000 = 67,200 kWh thermal/yr

Switching to polycarbonate saves 9,600 kWh thermal per year. At COP 2.5 that is 3,840 kWh electric, worth C$540/yr at C$0.14/kWh — recouping the upgrade in 12 years (good but not great).

The bigger insulation win is adding a Ludvig Svensson XLS-15 thermal screen, which drops night U-equivalent from 4.0 to 1.8 W/m²·K. That saves another 30 percent of heating cost annually and pays back in 4–6 years.

Supplemental lighting — sized for Canadian latitude

Canadian greenhouses sit at 42–60°N latitude. December daylight at 49°N is 8 hours of low-angle sunlight — well below what most crops need. From Agriculture and Agri-Food Canada’s controlled-environment guide:

  • Leafy greens (lettuce, kale, baby spinach, Asian greens): 80–120 W/m² LED, 5–6 hours supplemental.
  • Microgreens: 100–150 W/m², 12 hours/day on staged benches.
  • Brassicas: 100–150 W/m², 5–6 hours.
  • Tomatoes, peppers, cucumbers: 200–300 W/m², 8–10 hours — only economic in commercial-scale greenhouses (Leamington, Delta) with co-generation.
  • Cannabis (medical and recreational, Health Canada licensed): 400–600 W/m², 12–18 hours.

LED efficacy in 2026 — Heliospectra, Sollum, Fluence, and Quebec-manufactured Solartech — sits at 2.8–3.1 µmol/J. Replace any HPS or T5 fluorescent before sizing PV.

Worked example — 100 m² double-poly greenhouse in Ottawa

A homesteader’s 100 m² double-poly greenhouse near Ottawa, ASHP-heated, with leafy greens through the winter:

  • Glazing: double polyethylene inflated, U = 4.0 W/m²·K
  • Envelope: 200 m²
  • Climate: cold (Ottawa), HDD18 = 4500 K·day
  • Heat pump: cold-climate ASHP, average COP 2.5
  • Lighting: 90 W/m² LED, 5 hr/day, 210 days/yr
  • Fans + circulation: 5 kWh/m²/yr

Computations:

  • Heat thermal: 4.0 × 200 × 4500 × 24 / 1000 = 86,400 kWh/yr
  • Heat electric: 86,400 / 2.5 = 34,560 kWh/yr
  • Lighting: (90 × 100 / 1000) × 5 × 210 = 9,450 kWh/yr
  • Fans: 100 × 5 = 500 kWh/yr
  • Total electric: 44,510 kWh/yr
  • Annual bill at C$0.14/kWh: C$6,231
  • PV size: 44,510 / (4.0 × 365 × 0.77) = 39.6 kW
  • PV cost at C$2,300/kW: C$91,080
  • Simple payback: 91,080 / 6,231 = 14.6 years

The 39.6 kW system is large — most domestic roofs in Canada cap out at 12–15 kW, so plan a hybrid roof + ground-mounted PV array or accept partial offset. Adding a thermal screen to the greenhouse drops heating by 30 percent (and PV size to roughly 28 kW), shortening payback to ~10 years.

Common Canadian sizing mistakes

  • Ignoring thermal screens. A Ludvig Svensson or Phormium XLS-15 screen drops U-effective by 30–50 percent for less than C$15/m² installed. Add it before sizing PV.
  • Using HSPF without temperature derating. HSPF is a US Region IV (4°C) rating. CSA 745 cold-climate Canadian HSPF rates COP at −15°C and −25°C — much lower than the placard HSPF. Use COP at the local 99% design temperature.
  • Forgetting snow load. NBCC 2020 Climate Data puts Ottawa at 2.4 kPa ground snow, Quebec City at 4.1 kPa. Greenhouse structure must be engineered for it. Polycarbonate panels deflect under heavy snow; double-poly inflated handles it better.
  • Skipping the Greener Homes Loan. It is interest-free up to C$40,000 over 10 years. Even if you don’t need the cash, the lifetime savings vs taking on a 5–7% home equity loan are substantial.
  • Quoting Ontario Hourly Ultra-Low Overnight (ULO) as the average rate. ULO at C$0.028/kWh only applies 11 PM–7 AM. Day rate is C$0.14/kWh+. Greenhouse heating loads run 24 hours; weight ULO by your actual run-time fraction.

Stacking Canadian incentives in 2026

  • Canada Greener Homes Loan — up to C$40,000 at 0% interest over 10 years for PV, batteries, heat pumps, and insulation retrofits.
  • Canada Greener Homes Grant (ASHP only) — up to C$5,000 toward a NRCan-certified cold-climate ASHP install.
  • Hydro-Québec LogisVert — C$5,400 toward a centrally-ducted ASHP, plus net-metering at full D-rate.
  • BC CleanBC Better Homes — C$4,000–C$11,000 for ASHP installs depending on income tier.
  • SaskPower Net Metering — credits exported kWh at full retail rate; rebate of C$0.20/W on PV install up to 100 kW.
  • Nova Scotia HomeWarming — covers up to 100% of insulation and heat pump costs for eligible households.
  • PEI Switch Programme — up to C$6,000 ASHP rebate.

Effective net cost on a C$78,000 PV + battery + ASHP greenhouse package after stacking can drop below C$45,000 in Ontario and Quebec. That is the math driving the 5× growth in NRCan-certified residential greenhouse PV permits across Canada between 2022 and 2025.

Sources

Frequently asked questions

How many solar panels does a Canadian greenhouse need?
A typical 100 m² double-poly hobby greenhouse in Ontario or Quebec heated to 12°C with a cold-climate air-source heat pump (HSPF 10, COP 2.5 at −15°C) plus 90 W/m² of LED supplemental light for 5 hours over 210 winter days needs about 33,000 kWh of electricity per year. At Ottawa's 4.0 peak sun hours that requires a 29 kW PV array — roughly 72 panels at 400 W each — and at NRCan-installed cost of C$2,300/kW post-Greener Homes Loan that is C$66,700 capex. After the federal Greener Homes Grant (heat pump portion only) and provincial PV rebates the payback at C$0.14/kWh runs at 11–14 years.
Will a heat pump work for a Canadian greenhouse in winter?
Yes if you spec a cold-climate ASHP rated by NRCan. Mitsubishi Hyper-Heat, Fujitsu XLTH, Lennox VRF, and Carrier Infinity Cold-Climate models hold COP 2.0 down to −25°C, validated in the CanmetENERGY Varennes test facility. Below −25°C the unit cycles to backup resistance, which is why most Canadian greenhouse owners pair a 24 kBtu cold-climate ASHP with a 5 kW electric resistance trim or a wood stove. Quebec greenhouses get the best economics at Hydro-Québec's residential D-rate of C$0.08/kWh; Ontario hourly Ultra-Low Overnight at C$0.028/kWh during 11 PM to 7 AM makes nighttime heating remarkably cheap.
What is the best greenhouse glazing for the Canadian climate?
Double polyethylene inflated film at U = 4.0 W/m²·K is the dominant glazing across Canadian commercial greenhouses — strong wind and snow loading per NBCC, low cost per square metre, and easy to replace after hail. For hobby and small commercial, twin-wall polycarbonate at U = 3.5 W/m²·K is the long-term winner. Single glass is a poor choice in any Canadian climate — U = 6.0 and brittle at −30°C. The Canadian Greenhouse Conference 2024 proceedings rate double-poly + thermal screen as the gold-standard envelope: U-equivalent drops to 1.8 W/m²·K with a deployed Ludvig Svensson XLS thermal blanket at night.
Can I run a Canadian greenhouse off solar in winter?
Yes for the lighting and fans, no for the heating. Canadian December solar irradiance at 45°N is roughly 20 percent of June values, so PV alone cannot offset peak winter heat. The practical pattern is grid-tied PV with summer surplus banked under Ontario Net Metering or Saskatchewan SaskPower NetMetering, drawn down through winter. A 12 kW PV array in Toronto banks roughly 15,000 kWh of surplus April–September that offsets 90 percent of heat-pump electricity from November–February. CanmetENERGY's monitored greenhouses in St-Bruno hit 78 percent annual PV offset using this pattern.
How much does a solar-powered Canadian greenhouse cost in 2026?
A turnkey 100 m² double-poly greenhouse with 15 kW NRCan-installed PV, an 18 kWh battery, and a Mitsubishi 24 kBtu Hyper-Heat ASHP runs about C$78,000–C$110,000 in 2026 before incentives. The greenhouse structure is C$18,000–C$30,000, PV at C$2,300/kW is C$34,500, battery C$11,000, and the cold-climate ASHP C$14,000–C$22,000 installed. The Canada Greener Homes Loan covers up to C$40,000 interest-free; the federal Greener Homes Grant covers up to C$5,000 of the ASHP; and Quebec, BC, and Yukon offer C$3,000–C$8,000 in additional provincial rebates.

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