What Winter Heating Really Costs, by Greenhouse Type
Purchase price is easy to compare. But the cost of holding temperatures that make your plants happy across seasons is more complicated. The calculator below runs the math for different greenhouse structures based on the physics of their frames, glazing, and other features: published U values, R values, airtightness, climate normal temperatures for your zip code, and energy costs for different ways of heating a space. We designed the Growing Dome to perform in this test, but the results are as fair as we can make them, and we give the alternatives the benefit of the doubt if we had to make any assumptions. All assumptions are disclosed in the open on the page.
Calculate what heating a greenhouse costs
Enter your zip code for localized results. Select a growing dome and another similarly sized greenhouse type, select your seasonal goals, and what heater you use (or would be mostly likely to use). We prepopulate energy prices based on national averages, but enter your personal rates for more accurate calculations.
Where these numbers come from
The Growing Dome
22' Growing Dome
Versioned engine constants (v1.1) — each value carries its citation in the published methodology.
- Envelope UA
- 285 BTU/h·°F
- Growing area
- 373 ft²
- Thermal storage capacity
- 113 kBtu
- Continuous storage credit
- 8.1 kBtu/h
- Thermal capacitance
- 9,200 BTU/°F
- Interior volume
- 2,790 ft³
Comparison Structure
CoverLite 6 mm twin-wall, U-0.62/R-1.61 center-of-glazing (same datasheet as the seeded 10×20 kit), zero thermal-bridging penalty for the steel frame — deliberately generous. Airtightness baseline 1.0 ACH, the methodology's dome baseline. Half-ellipse geometry, 14′ span × 9′ ridge × 28′ long; full footprint counted as growing area. Thermal capacitance scaled from the seeded kit's declared 420 BTU/°F by interior volume. Service life 12 years, matching the seeded kit's basis. Corrections welcome.
- Envelope UA (derived)
- 610 BTU/h·°F
- Growing area
- 392 ft²
- Thermal storage capacity
- 0 kBtu
- Continuous storage credit
- 0 kBtu/h
- Thermal capacitance
- 930 BTU/°F
- Service life
- 12 years
- Sources verified
- 2026-07-27
How we ran the numbers
- Seasonal model: September–May monthly integration of day/night heating loads from NASA POWER climatology for your ZIP, with solar gain applied identically to both structures — a simplification that is generous to the smaller structure — and nightly thermal-storage banking. Full model: Climate & HVAC Sizing Methodology.
- Comparisons are nudged size-for-size: structures whose growing area is within 1.5× of the selected dome's are listed first, mismatched pairings are flagged rather than blocked, and the per-square-foot figures are the fair cross-size metric. The initial dome size is the closest match to the default comparison structure.
- Dome parameters for the selected 22' Growing Dome: envelope UA 285 BTU/h·°F, growing area 373 ft², nightly storage capacity 113 kBtu, continuous storage credit 8.1 kBtu/h, thermal capacitance 9,200 BTU/°F. The continuous credit is the methodology's design-night discharge quantity, disclosed here for symmetry with the preset declarations above — the seasonal model banks storage nightly rather than applying a continuous offset, so it never enters the cost math for either structure.
- Mechanism constants: Propane: 91,500 BTU per gallon at 80% vented-combustion efficiency. Natural gas: 100,000 BTU per therm at 80% vented-combustion efficiency. Electric resistance/IR: 3,412 BTU per kWh. Electric heat pump: 3,412 BTU per kWh at a fixed seasonal COP of 2.3. Vent-free combustion units convert more of the fuel to heat but add moisture the space must manage.
- Default fuel prices are EIA U.S. residential averages — propane $2.55/gallon (winter 2025–26 season average), natural gas $1.57/therm ($16.25/Mcf, March 2026), electricity $0.19/kWh (18.83¢, April 2026). They prefill the price field and are always editable — replace them with your local price for a real estimate.
- For heat-pump capacity sizing at design temperatures, use the Climate Calculator.
- Wood and pellet heating are excluded by design, not omission — their delivered cost depends on fuel handling and appliance efficiency ranges this comparison cannot state fairly.
- Cold-tail nights: nightly temperatures are modeled as a normal spread around the monthly mean, anchored to the zone's 99% winter design temperature (σ = (January mean low − T₉₉) ÷ 2.33, clamped 3–12 °F; each run's σ is shown with the season table). Nightly thermal storage offsets each night's first kBtu — equivalent to lowering the protected temperature — so high-mass structures ride out cold-tail nights that low-mass structures must heat through. Day-side loads remain monthly-mean based, and multi-week anomalies beyond the 1% tail (polar events) are still not priced.
- Preset-specific assumption disclaimers (glazing values, bridging, airtightness) live in each structure's basis sheet above. Corrections are welcome.
