Size your heater using real greenhouse heat-loss math. Tweak glazing, insulation, and air changes quickly. See energy, runtime costs, and safety margin instantly here.
Enter geometry, envelope performance, infiltration, and energy details. The form uses a responsive grid: 3 columns on large screens, 2 on small, 1 on mobile.
| Scenario | Size | Cover | ΔT | ACH | Safety | Required output | Energy/day |
|---|---|---|---|---|---|---|---|
| Backyard winter | 10 m × 4 m × 2.2 m | Double poly film | 20 K | 1.5 | 15% | ~9.5 kW | ~134 kWh |
| Small tunnel | 6 m × 3 m × 2.0 m | Single poly film | 15 K | 2.0 | 10% | ~5.7 kW | ~67 kWh |
| Insulated structure | 12 m × 6 m × 3.0 m | Well-insulated panels | 25 K | 1.0 | 20% | ~10.8 kW | ~153 kWh |
Greenhouse heating demand is driven by the temperature difference between your inside setpoint and the local design minimum. Because ΔT raises losses linearly, a realistic outside temperature is critical. Many growers size for a cold, typical winter night and add a safety margin to cover occasional colder events and operational disturbances.
The U-value describes how quickly heat passes through the cover per square meter and degree. Moving from a single layer to a double layer can substantially cut required heater capacity. Repairs, sealed joints, and tight doors often deliver savings comparable to upgrading glazing, because gaps bypass insulation entirely.
Air changes per hour (ACH) combine leakage and any planned fresh-air exchange. In lightly built structures, infiltration can dominate total heat loss, especially in windy sites. Adjust the wind multiplier to reflect exposure, and consider night curtains or baffles to reduce drafts across plant benches.
A heater should meet calculated losses plus safety margin so temperatures recover after door openings and brief cold snaps. If required output is close to installed capacity, long runtimes are expected and temperature control becomes less stable. Two smaller heaters can improve redundancy and allow staged operation.
Operating cost depends on delivered heat, heater efficiency, and fuel price. Electric systems are simple to control, while gas and liquid fuels may reduce cost per kWh depending on local rates. Compare monthly fuel use to the estimate, then tune ACH and U-value until predictions match your real consumption.
Use a representative cold winter night for your area, then add safety margin. Sizing only for record lows often oversizes equipment and inflates costs for typical operation.
Start with the closest cover preset. After a few weeks, compare predicted energy to your measured use and adjust U-value or ACH until the estimate aligns with reality.
Leaking air removes warmed air that you paid to heat. In windy conditions, infiltration losses can exceed conduction, especially with loose doors, torn film, or unsealed seams.
Yes, if you have a measured wall-and-roof area or manufacturer data. It improves accuracy for tall end walls, complex shapes, or when you use internal curtains at night.
Use the rated efficiency for your appliance. If unknown, choose a conservative value. Short cycling, poor maintenance, and installation issues can reduce delivered heat and raise fuel use.
Seal leaks, add a second glazing layer, and use nighttime thermal curtains. Reducing ACH and improving U-value typically lowers required kW more than minor setpoint changes.
Daily weather varies, and sun can offset heating on bright days. Door openings, humidity control, and fans also change loads. Calibrate ACH and U-value using measured fuel use.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.