Calculator
Propane usage calculator
Gallons per hour, month, and year from an appliance's Btu rating, with tank life and refill frequency.
Propane carries about 91,452 Btu per gallon, per the EIA energy conversion tables, so gallons are total Btu input ÷ 91,452. Cylinder sizes use 4.24 lb of propane per gallon: a properly filled 20-lb cylinder holds about 4.7 gallons. Tank sizes are nominal shell capacity; tanks fill to at most 80% (the 80% rule) and the gauge reads percent of the shell. The state price is the EIA weekly state residential survey figure, published October through March; between surveys the last surveyed price prefills, labeled with its date, and stays editable. Everything here is arithmetic on the numbers you enter — weather, burner cycling, appliance condition, and gauge accuracy all move real usage. It is an estimate, not delivery scheduling, tank sizing, or safety advice.
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How propane usage is calculated
Gas appliances are rated by Btu input per hour — the fuel energy the burner draws when it fires, printed on the nameplate or spec sheet. Propane carries about 91,452 Btu per gallon, so consumption is one division:
gallons = Btu per hour × burner hours ÷ 91,452
A 100,000 Btu furnace burns about 1.09 gallons per hour of burner time. The number that takes judgment is the hours: a furnace that is "on" for ten hours may fire the burner for only four or five of them, which is what the duty-cycle field represents. Entering actual burner-on hours pairs with a 100% duty cycle; entering thermostat or schedule hours pairs with a lower one.
One caution on the rating itself: nameplates list input Btu. The heat delivered to the room is lower by the appliance's efficiency, and this calculator wants the input figure — an output rating understates fuel use, and discounting an input rating by efficiency double-counts it.
Propane gallons per hour by Btu rating
At full input, consumption scales directly with the rating:
| Btu input rating | Gallons per hour |
|---|---|
| 30,000 (fireplace insert, cooktop) | 0.33 |
| 50,000 (patio heater, small furnace) | 0.55 |
| 75,000 (tankless water heater, mid furnace) | 0.82 |
| 100,000 (whole-home furnace) | 1.09 |
| 150,000 (large furnace, boiler) | 1.64 |
| 200,000 (pool heater, low end) | 2.19 |
| 400,000 (pool heater, high end) | 4.37 |
Real appliances cycle and modulate, so average consumption over a day usually sits well below the full-input rate.
How long a propane tank lasts
Tank names refer to nominal shell capacity, and a tank is filled to at most 80% of it, so a "500-gallon" tank holds about 400 gallons full. The gauge reads percent of the shell: a 60% reading on a 500-gallon tank is 300 gallons. The Tank life tab counts the gallons between the current reading and a reserve level you pick, then divides by daily use — 300 gallons down to a 20% (100-gallon) reserve is 200 usable gallons, about 50 days at 4 gallons a day.
What changes actual usage
The arithmetic is exact; the inputs are the estimate. Outdoor temperature drives furnace burner hours more than any other factor, which is why the same house burns three times the propane in January as in March. Insulation, air leakage, and thermostat setting move the runtime; appliance age and condition move the efficiency; hot-water demand and generator load vary week to week; and float-style tank gauges read coarsely, commonly a few points off. The result on this page is the arithmetic of the numbers entered, not a metered reading.
Annual propane usage by home type
What a home burns in a year depends far more on what runs on propane than on any single number. EIA's Residential Energy Consumption Survey and its winter fuels reporting put whole-home heating as the dominant driver, with water heating, cooking, clothes drying and standby generators layered on top. The ranges below are a starting point, not a bill:
| Home or usage type | Typical annual gallons |
|---|---|
| Cooking and water heating only (propane, no space heat) | 200 to 300 |
| Whole-home heat, average climate | 800 to 1,200 |
| Whole-home heat, cold climate | 1,500 or more |
EIA's own regional averages for a recent heating season, from its Winter Fuels Outlook, put the typical propane-heating household at about 641 gallons for the season in the Midwest and about 519 gallons in the Northeast, both single-season heating totals rather than a full year including summer cooking and hot water load. The Appliance usage tab above turns any of these ranges into a per-hour, per-month or per-year estimate once the appliances actually running, and for how long, are known.
Adjusting for a warmer or colder than normal winter
Every range above assumes a roughly average winter. The real driver is heating degree days, EIA's standard measure of how much heating a day calls for: each day's average temperature is subtracted from a 65 degree Fahrenheit base, and the shortfall, zero on a mild day, is summed across the season. A winter with more heating degree days than normal burns more propane at the same house and the same thermostat setting; a milder one burns less.
To adjust an estimate for how a season is actually running rather than guess, compare it against a normal year: this site's own propane-weighted heating degree days tracker, built from the NOAA Climate Prediction Center's weekly data, reports the season-to-date total against its normal. A reading 8% above normal scales a baseline estimate up by the same 8%; a season running below normal scales the estimate down the same way. It is an approximation, since a house's actual response to weather is not perfectly linear with degree days (insulation and thermostat behavior both blunt the effect at the margins), but it comes far closer than assuming every winter behaves like an average one, and it costs nothing more than one extra multiplication once the Appliance usage tab above has produced a baseline gallons-per-year figure to scale.
Common questions
How do you calculate propane usage from a Btu rating?
Multiply the appliance's Btu input rating by its burner-on hours, then divide by 91,452 — the Btu in a gallon of propane. A 100,000 Btu furnace that fires 4 hours a day burns about 4.4 gallons a day. Use the input rating from the nameplate, not the heat output.
How many gallons of propane does a 100,000 Btu appliance use per hour?
About 1.09 gallons for each hour the burner fires at full input (100,000 ÷ 91,452). Cycling and modulation usually put average use below that, which is what the duty-cycle field accounts for.
How long will a 500-gallon propane tank last?
It depends on the gauge reading and the burn rate, not the tank name alone. At a 60% gauge a 500-gallon tank holds about 300 gallons; run down to a 20% reserve that is 200 usable gallons — 50 days at 4 gallons a day, 100 days at 2. The Tank life tab runs this count for any size, gauge, and usage rate.
How much propane does a generator use?
It varies with the generator's size and the electrical load it carries, not just its rating — a 22 kW standby unit commonly burns 2 to 3.5 gallons an hour between half and full load. Manufacturer fuel-consumption tables list gallons per hour at half and full load; those figures times expected run hours convert directly in the Appliance usage tab.
How much propane is in a 20-pound cylinder?
About 4.7 gallons when properly filled: propane weighs about 4.24 pounds per gallon, and 20 ÷ 4.24 ≈ 4.7. Actual fill varies a little with temperature and filling equipment.
Why does actual usage differ from the estimate?
The formula is exact, but the inputs move: outdoor temperature swings burner hours, appliances cycle and modulate below their rated input, equipment condition drifts, and tank gauges read coarsely. Weeks of identical settings can burn noticeably different gallons.