Greenhouse Heating Cost Calculator
Estimates the monthly fuel cost to heat a greenhouse based on its floor area, glazing, the inside-outside temperature gap, fuel price, and heater efficiency. Helps growers budget winter heating expenses.
Last updated: September 2026
Formula below · 2 sources (usda.gov, Wikipedia) · Updated Sep 2026
Compare with similar
About this calculator
Greenhouse heat loss follows Q = U × A × ΔT, the standard heat-loss formula in extension greenhouse guides. U is the glazing's heat-transfer coefficient (about 1.1 BTU/hr/sq ft/°F for single glass, 1.2 for single poly, 0.7 for double-wall poly and 0.65 for insulated double glass). A is the glazed surface area, taken as 1.8 × the floor area, typical of gable and hoop houses. ΔT is the target inside temperature minus the average outside temperature. Monthly heat = U × A × ΔT × 24 × 30 BTU. Dividing by 140,000 BTU per gallon (heating oil or diesel) and by the heater efficiency gives gallons of fuel, and multiplying by the fuel price gives cost: Monthly Cost = floorArea × 1.8 × U × (insideTemp − outsideTemp) × 720 × fuelCost ÷ 140,000 ÷ (efficiency/100). For propane (about 91,500 BTU per gallon), enter your propane price × 1.53; for natural gas, enter your $/therm × 1.4. Use the month's average outside temperature for budgeting; for sizing the heater, use the design low temperature instead. Air leakage typically adds 10-30% and daytime solar gain subtracts some, so treat the result as a planning estimate.
How to use
Say you have a 5,000 sq ft single-poly greenhouse (U = 1.2), maintaining 65°F inside when the month averages 25°F outside (a 40°F difference), with heating oil at $2.50 per gallon and an 85% efficient heater. Glazed area = 5,000 × 1.8 = 9,000 sq ft. Monthly heat = 9,000 × 1.2 × 40 × 720 = 311,040,000 BTU. Fuel = 311,040,000 ÷ 140,000 ÷ 0.85 ≈ 2,613.8 gallons. Monthly cost ≈ 2,613.8 × $2.50 = $6,534.45. Switching to double-wall poly (U = 0.7) cuts that to about $3,811.76.
Frequently asked questions
How does glazing type affect greenhouse heating costs in winter?
Single-layer polyethylene film has the highest heat loss rate (roughly 1.1 BTU/hr/sq ft/°F), while double-layer inflated film cuts that nearly in half. Twin-wall polycarbonate panels offer better insulation still, and glass with thermal curtains can approach the performance of polycarbonate. Upgrading from single to double-layer poly on a large greenhouse can reduce heating fuel consumption by 30–40%, paying back the investment within one or two heating seasons depending on fuel prices. Choose the glazing option closest to your structure; the calculator multiplies its U-value by 1.8 × floor area.
What is the temperature difference I should use for greenhouse heating calculations?
Use the design temperature difference, which is the gap between your desired interior growing temperature and the lowest expected outdoor temperature for your region (typically a 97.5% or 99% winter design temperature from ASHRAE climate data). For example, if you grow tomatoes at 60°F and your area's winter design low is 10°F, use a 50°F difference. Using average temperatures will underestimate peak heating demand and risk crop loss on cold nights. Always design for the worst-case scenario and then model average conditions separately for budget forecasting.
How can I reduce greenhouse heating costs without sacrificing crop temperature?
The most effective strategies are adding thermal mass (water barrels, concrete floors) to store daytime solar heat, installing thermal blanket curtains that close at night to cut radiative heat loss, sealing air infiltration at vents and door gaps, and using zone heating to keep only occupied benches at full temperature. Switching from propane to natural gas or biomass boilers can also substantially lower fuel cost per BTU. Many growers recoup insulation investments within a single heating season in cold climates where fuel bills otherwise dominate operating costs.