Know your fuel cost before winter hits. Enter usage, price, and efficiency for clear totals. Download reports and tune settings for smarter gardening today.
| Use case | Usage rate | Hours/day | Days | Price | Efficiency |
|---|---|---|---|---|---|
| Small greenhouse heater | 1.2 therm/hr | 6 | 30 | $1.80/therm | 90% |
| Propagation tunnel | 0.9 therm/hr | 5 | 21 | $1.65/therm | 88% |
| Outdoor kitchen burner | 45,000 BTU/hr | 1.5 | 12 | $0.000055/BTU | 60% |
Examples are illustrative. Always use your meter and bill data.
1) Total usage in entered units
TotalUnits = UsageRate × HoursPerDay × Days
2) Unit conversion through kWh
Entered_kWh = TotalUnits × kWhPerUnit
For m³, kWhPerUnit = kWhPerM3 (user input).
3) Gas input energy and useful heat
If usage is useful heat: Gas_kWh = Entered_kWh ÷ Efficiency
If usage is gas input: Useful_kWh = Gas_kWh × Efficiency
4) Price normalization
PricePerkWh = PricePerUnit ÷ kWhPerUnit(PriceUnit)
5) Cost totals
VariableCost = Gas_kWh × PricePerkWh
FixedCost = ServiceCharge + (DailyFixed × Days)
Subtotal = VariableCost + FixedCost
Tax = Subtotal × Tax%
Total = Subtotal + Tax
Garden heating often runs for long periods, so small tariff differences become meaningful. This calculator standardizes gas use into kilowatt‑hours, letting you compare therms, cubic meters, or BTU on one cost basis. When you switch price units, the derived price per kWh updates instantly, making supplier quotes easier to evaluate. Use input basis when your meter reads volume but the invoice lists energy; conversion bridges the gap.
Efficiency matters because the plants feel useful heat, not fuel input. If you measure burner output or want to estimate delivered warmth, select useful heat and enter appliance efficiency. The tool then back‑calculates required gas energy. This is helpful when upgrading to higher‑efficiency heaters or adding insulation curtains in a greenhouse. Set realistic efficiency values for older unit heaters, and avoid counting standby losses unless included in measured output.
Fixed charges can dominate short billing cycles. Daily meter fees and one‑time service charges are added before tax, matching common utility billing logic. Including these items helps you plan a realistic winter budget, especially for small tunnels where variable gas use is low but account fees remain constant. If your region applies tax only to consumption, set service charge to zero and add it later for consistency.
Operational scheduling is where gardeners gain control. Use hours per day and days in period to model night‑only heating, frost protection weekends, or seedling propagation phases. Pair the result with temperature targets and ventilation plans to decide whether to reduce runtime or improve heat retention instead. Model shoulder seasons separately, because spring and autumn loads are usually lower than mid‑winter baselines.
Reporting supports decision making and record keeping. Download CSV to archive assumptions with your project notes, or export a PDF summary for clients, landlords, or farm managers. Recalculate with alternate prices or efficiencies to build scenarios, then choose the option that meets crop needs at the lowest predictable cost. Keep exports with date stamps to track pricing impacts and support clear year‑over‑year comparisons for planning.
Which unit should I choose for usage rate?
Use the unit you measure directly. If your heater is rated in BTU/hr, choose BTU. If you track therms or m³ from the meter, choose those. The calculator converts everything to kWh automatically.
What if my bill price is per cubic meter?
Select m³ as the price unit and enter the billed price. Then set the energy content value so the conversion matches your local gas quality. Your utility may list a conversion factor on the invoice.
How do I estimate efficiency for a greenhouse heater?
Check the equipment label or manual first. Older vented unit heaters may be around 70–85%, while condensing models can exceed 90%. Use a conservative value when planning budgets to avoid underestimating costs.
Do fixed charges and taxes apply to all users?
Many accounts include daily meter fees, service charges, and tax or VAT. If a line item does not apply, set it to zero. This keeps totals aligned with your local billing structure and improves comparisons.
Can I model short frost‑protection events?
Yes. Use a small number of days and the expected hours per day for the event. Add any one‑time service charge if it still appears on the bill. The per‑hour metric helps compare strategies quickly.
Why does the tool show cost per useful kWh?
Useful kWh reflects heat delivered to plants after efficiency losses. This metric helps compare heater upgrades, insulation improvements, or different fuels on a consistent delivered‑energy basis, rather than only on fuel input.
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.