LPG heater runtime and cost calculator
How long will your gas last? Enter the usable LPG fill and your heater manual's consumption at the setting you use. Add your refill price if you want a fuel-cost estimate.
Assumes a constant stated fuel rate and usable fuel fill. Results are burner-on hours, not days on a calendar. This does not test appliance safety or account for other appliances, cylinder delivery charges or actual useful-heat efficiency. Your entries stay in this page and are not saved by this tool.
LPG cylinders · Gas heater fuel and running cost
One kilogram of LPG lasts five hours in a heater consuming 200 grams per hour. At 300 grams per hour it lasts about three hours and twenty minutes.
The burner setting and the appliance's stated fuel consumption matter more than the number of panels or the brand name.
Runtime in hours = usable LPG kilograms × 1000 ÷ consumption in grams per hour. This guide covers cylinder LPG. It does not use kilograms as a shortcut for a piped-natural-gas bill.
Find the consumption for your heater and setting
Look in the model manual for LPG or propane consumption, usually in g/h or kg/h. Check the selected setting. A label in kW may describe heat output rather than fuel input, so do not substitute it directly into a fuel calculation.
If the manual gives 0.2 kg/h, that is 200 g/h. If it gives a range, calculate each relevant setting. Do not assume every three-panel heater has the same flow rate or that “low” is always one third of “high.”
| Usable LPG | 100 g/h | 200 g/h | 300 g/h |
|---|---|---|---|
| 1 kg | 10 hours | 5 hours | 3.33 hours |
| 5 kg | 50 hours | 25 hours | 16.67 hours |
| 11.8 kg | 118 hours | 59 hours | 39.33 hours |
These are arithmetic examples, not specifications for any named heater or a promise that a cylinder will deliver every nominal kilogram under all conditions. Use the actual fuel fill, not the total weight of cylinder plus gas. Decimal hours are fractions of an hour: 3.33 hours is about 3 hours 20 minutes, not 3 hours 33 minutes.
Turn hourly fuel use into local cost
At an illustrative PKR 300/kg and 200 g/h, fuel costs 0.2 × 300 = PKR 60/hour. Four burner-on hours use 0.8 kg and cost PKR 240. Over 30 identical days that is 24 kg and PKR 7200. These are original hypothetical inputs, not today's LPG price or a typical household bill.
If your refill receipt lists only a fuel charge and a known net fill, divide that fuel charge by net kilograms. Separate deposits, cylinder purchase, delivery and other fees before deciding whether you want a fuel-only cost or an all-in refill cost. State which you use.
Record: net refill kg, fuel charge, heater model, fuel type, rated g/h, setting and daily burner-on hours.
Calculate: daily kg = g/h × hours ÷ 1000. Estimated remaining kg = starting kg minus cumulative use.
This is a bookkeeping estimate, not a cylinder gauge or leak test. Changing settings, other appliances sharing the cylinder and uncertain starting fill reduce accuracy. Have the supplier or qualified technician assess abnormal consumption; do not adjust regulators or test for leaks with a flame.
What if the gas rating is in MJ/h?
Australian heaters often show a fuel-input rating in MJ/h. If your bill is priced per MJ, multiply the applicable input MJ/h by running hours and the price per MJ. Add electricity used by fans or controls separately where relevant.
For LPG mass conversion, you also need a compatible calorific value and its basis. IEA Advanced Motor Fuels lists LPG lower heating values around 44–46 MJ/kg. Using an explicitly assumed 45 MJ/kg, 9 MJ/h of fuel input corresponds to 9 ÷ 45 = 0.2 kg/h. Do not mix a gross/higher-heating-value rating with a net/lower-heating-value conversion without reconciling the basis.
For a real specification reference, Rinnai Australia's 1005FT page lists gas input separately from output and provides installation/operation documents. Check fuel variant and rating basis in the exact manual. This is a manufacturer reference, not an affiliate recommendation or a claim that this model uses the table's assumed rates.
LPG and piped natural gas need separate calculations
A cylinder's kg price is not a natural-gas tariff. Piped gas may be billed using volume, calorific-value adjustments and energy units such as MJ, kWh or MMBtu. Use the bill's conversion method and your supplier's current tariff. Do not assume 1 cubic metre of natural gas equals 1 kg of LPG.
The same mass-flow method can estimate an LPG geyser's fuel use only when its own manual supplies the applicable fuel rate. Count burner-on time during hot-water demand; a room-heater's assumed g/h is not a geyser specification.
Is gas cheaper than an electric heater?
Compare the cost of equal useful heat, not merely equal hours. If a hypothetical LPG price is PKR 300/kg, its lower heating value is assumed 12.5 kWh/kg, and useful-heat efficiency is assumed 80%, then useful heat costs 300 ÷ (12.5 × 0.8) = PKR 30/kWh of useful heat. A resistance heater at an assumed PKR 50/kWh electricity is approximately PKR 50 per kWh delivered indoors.
Those assumptions do not establish a universal winner. Real fuel prices, heat losses, installation, ventilation requirements, servicing and electricity for gas controls can change the comparison. A heat pump needs its seasonal performance included and is not equivalent to a resistance heater.
Use your own electricity rate
Open the electricity bill and device estimator
Read how to calculate appliance electricity units and our methodology and limits. The device estimator calculates electricity; it does not turn LPG kilograms into an electricity bill.
Prepared 2 November 2026. Rates, prices, efficiency and schedules in worked examples are assumptions. No household test, live LPG price, affiliate arrangement or universal indoor-safety approval is claimed.
Choose the right calculation for your next question
Heating a room with electricity? Use the electric heater running-cost guide for 1000 W, 1500 W and 2000 W settings and thermostat cycling.
Heating water instead? Read the electric geyser and water-heater guide to distinguish element-on time from time connected to power.
For a household-wide check, use the seven-day energy worksheet before deciding which appliance to replace.
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