Greenhouse Operating Cost Calculator
Calculate monthly and seasonal greenhouse operational expenses including winter heating energy, summer cooling fans, supplemental LED grow lights, and water.
Winter Heating Energy & Electrical Systems
Greenhouse Thermal & Energy Formula
Heating Heat Loss (BTU/hr) = Surface Area (SqFt) × (Inside Temp - Outside Temp) × U-Factor Heat Transfer; Heating Cost = Total Seasonal BTUs / Fuel Efficiency × Fuel Price; Electric Cost = (Fan Watts + Lighting Watts) / 1000 × Hours × Electricity Rate- U-Factor (Heat Loss): Single glass/film = 1.10–1.20; Double poly inflated film = 0.70; 8mm Twin-wall polycarbonate = 0.58; Triple-wall = 0.42.
- Surface Area: Total exterior glazing envelope (roof arches + sidewalls + end walls), typically 2.0x to 2.8x the floor footprint.
- Heating Fuels: Natural Gas ($1.20–$1.80/Therm), Propane ($2.20–$3.50/Gallon, 91,500 BTU/gal), Electric heat pump.
Step-by-Step Worked Example
Calculation Steps:
- Calculate propane gallons per month: 15,000,000 / 73,200 = 204.9 gallons
- Calculate monthly heating cost: 204.9 gal × $2.75 = $563.48 / month
- Add monthly electric fan and light energy: $563.48 + $65.00 = $628.48 / month
- Calculate full 4-month winter operating cost: $628.48 × 4 months = $2,513.92
- Calculate cost per square foot: $2,513.92 / 500 sq ft = $5.03 / sq ft
How to Use This Calculator
- 1Enter greenhouse floor area and estimated exterior glazing surface area.
- 2Specify target minimum night temperature and your local average winter temperature.
- 3Select heating fuel source (propane, natural gas, electric heat pump) and energy prices.
- 4Add daily operating hours for exhaust/circulation fans and supplemental grow lights.
- 5Review monthly heating and electrical bills along with total seasonal expenses.
Assumptions & Limitations
- Heating calculations use the American Society of Agricultural and Biological Engineers (ASABE) greenhouse heat-loss standards.
- Excludes non-energy inputs (fertilizer, potting soil, seed plugs).
Frequently Asked Questions
What is the biggest expense in operating a greenhouse?
Winter heating is overwhelmingly the largest operational expense, often accounting for 70% to 85% of total annual operating budgets in northern climates (Zones 3 through 6).
How can I reduce greenhouse heating costs in winter?
Install thermal heat-retention energy curtains to pull across at sunset, seal air leaks around doors and vents with foam gaskets, add 1-inch bubble wrap insulation to northern end walls, and use high-efficiency infrared tube heaters or unit heaters.
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