Propane Consumption Calculator: How Long Will Your Tank Last?

What the Propane Consumption Calculator Does

A propane consumption calculator converts appliance BTU ratings into gallons burned, tank days remaining, generator runtime and dollar cost. It totals every propane load in a rural home or RV, so one result covers the furnace, water heater, range, dryer, fireplace and backup generator. Nothing gets missed.

Most single-purpose tools only tackle one slice of the problem, such as how long a fire pit burns or how many hours a heater runs. This one doesn’t. Whole-home heating, generator runtime, tank planning and cost all sit on a single page.

How to Use the Calculator

List every propane appliance with its BTU input rating and daily run hours, then add your tank size, gauge reading and local price per gallon. Results come back as gallons per day, days left in the tank and daily cost, so you can schedule each refill ahead of time. Refills stop being a guess.

1. List every appliance connected to the tank, including the generator.
2. Enter each appliance’s BTU per hour input rating from its data plate or owner’s manual.
3. Type in the hours each appliance runs on a typical day.
4. Record the tank size in gallons and the current gauge percentage.
5. Copy your price per gallon from your latest supplier invoice.
6. Add the HDD for your location and your furnace AFUE to estimate a full heating season.
7. Review the results and schedule a refill before the gauge reaches 20%.

Inputs and Outputs Explained

The calculator needs five core inputs and two optional heating inputs. Core inputs cover BTU rating, run hours, tank size, gauge reading and price per gallon. HDD and AFUE handle heating. From those values, the calculator works out gallons per hour, gallons per day, days remaining, generator runtime and cost.

Inputs

Outputs

How Do I Calculate Propane Usage?

Divide an appliance’s BTU per hour input rating by 91,452, the BTU content of one gallon of propane, then multiply by hours of use. An 80,000 BTU furnace running 8 hours burns 640,000 BTU, which works out to about 7.0 gallons (26.5 L) per day.

Working in metric? Divide by about 24,160 BTU per liter instead, since that’s the energy in a single liter of propane.

Always use the input rating. Input BTU measures the fuel a burner consumes, while output BTU only measures the heat that actually reaches your home.

How Much Is Propane to Heat a House?

The cost to heat a house with propane equals the gallons used in a season multiplied by your local price per gallon. Seasonal gallons hinge on heat loss and climate. Furnace efficiency matters too. No verified national figure for a typical home is available, because a Maine farmhouse burns far more than a Georgia ranch.

Prices swing by state and season. Before you run the numbers, check the EIA Heating Oil and Propane Update for residential prices in participating states. To track the cost propane heat adds each month, compare actual deliveries with the estimate.

Heating Degree Days and AFUE

Season gallons come from one formula that converts heat loss and climate into fuel.

For heat loss per °F, ask a heating, ventilation and air conditioning (HVAC) contractor for a Manual J design heat loss. Then divide that number by the gap between your indoor and outdoor design temperatures. That’s your figure.

Pull HDD values for your location from the degree day data published by NOAA, using the station closest to your home. Local numbers matter.

AFUE is the share of fuel energy that ends up as usable heat. A 95% AFUE furnace turns 95 of every 100 BTU it burns into heat for the house. The rest is lost.

Here’s a worked example. The sample home loses 500 BTU per hour per °F and sees 6,000 HDD per season, with costs based on an illustrative $3.00 per gallon rather than a market price.

In this example, the 95% furnace saves about 155 gallons (587 L) over the heating season compared with the 80% unit. The gap repeats every winter.

How Long Does Propane Last in a Generator?

A generator runs for your usable gallons divided by its gallons per hour at actual load. Find that burn rate on the manufacturer’s spec sheet. Runtime drops as load rises, so a generator at full load drains a tank faster than the same unit at half load.

Swap in your own model’s burn rate. A generator that uses less than 2 gallons (7.6 L) per hour runs longer on the same supply, and a hungrier unit runs shorter.

Cold weather adds a catch. Small cylinders struggle to vaporize enough gas for large generators when temperatures drop, which is why standby units connect to American Society of Mechanical Engineers (ASME) tanks.

How Long Will a Propane Tank Last?

A propane tank lasts its usable gallons divided by the gallons burned each day. Usable gallons equal size times gauge reading. Under the 80% fill rule in National Fire Protection Association (NFPA) 58, a full 500-gallon tank reads about 80% and holds roughly 400 gallons (1,514 L).

Picture a full 500-gallon tank feeding a home that burns 8.2 gallons per day across all of its propane appliances. That tank lasts about 49 days.

Cylinders follow the same math. A 100 lb cylinder holds about 23.6 gallons (89.3 L), or roughly 2.16 million BTU, so a 40,000 BTU per hour load runs about 54 hours on one cylinder.

That 100 lb size works well for grills, patio and garage heaters, portable generators and some water heaters in small cabins. Whole-house furnaces need ASME tanks.

Example Use Cases

These two rural examples run the calculator’s math on sample appliances, a 500-gallon tank and an illustrative $3.00 per gallon. Swap in your own data plate ratings, gauge reading and supplier price before the results apply to your property.

Rural Farmhouse Winter Estimate

That farmhouse burns 8.2 gallons (31.0 L) per day. At the sample price, the daily bill comes to $24.60, which adds up quickly over a long stretch of cold weather.

Its 500-gallon tank reads 70%. That leaves 350 gallons (1,325 L), enough to keep all three appliances running for about 43 days.

Plan the order early. To refill before the gauge hits 20%, the owner needs to call the supplier within about 30 days of this reading.

Backup Generator During an Outage

Start with a full 500-gallon tank. It holds 400 gallons of usable propane, the most a tank that size carries under the 80% fill rule.

Now picture a standby generator whose spec sheet lists 3 gallons (11.4 L) per hour at half load during an extended outage. That’s 72 gallons per day.

Home loads still run. Add their 8.2 gallons per day, and the tank supports about 5 days of continuous outage before it runs dry.

Tips for Accurate Estimates

Accurate propane estimates come from real inputs: input BTU ratings, honest run hours, a current local price and a gauge reading taken at the same time each week. Check each estimate against delivery tickets. If they disagree, adjust the run hours until the calculator matches what the truck actually delivers.

• Use the input BTU rating, not the output rating, from each data plate.
• Count generator exercise cycles, which burn fuel even without an outage.
• Lower the thermostat at night to cut furnace run hours.
• Seal air leaks and add attic insulation to reduce heat loss per °F.
• Install a tank monitor for remote gauge readings and automatic delivery alerts.
• Order a refill before the gauge drops to 20%, especially ahead of winter storms.

Got questions?

Frequently Asked Questions