How Long Does a 500-Gallon Propane Tank Last? (With Real Numbers)
A 500-gallon propane tank is filled to 80%, so it holds about 400 usable gallons. At whole-house heating rates of 4–8 gallons a day that lasts roughly 50–100 days; with only a water heater and stove (around 2 gallons a day) it can last over six months. Published answers range from 19 days to a year because they assume different burn rates, so use your own.
Plug in your numbers with the tank duration calculator.
Days of propane by daily use (400 usable gallons)
| Gallons per day | Days | Typical situation |
|---|---|---|
| 2 | 200 | Water heater and stove |
| 4 | 100 | Mild-weather heating |
| 8 | 50 | Cold-weather heating |
| 12 | 33 | Large or leaky home in a deep freeze |
Why online answers disagree
Some pages count 500 gallons instead of 400. One widely copied example divides 500 gallons of energy by a furnace running nonstop at 100,000 BTU per hour, which gives 19 days. Real furnaces cycle on and off, so that is a worst case, not an average.
Find your own burn rate
Divide the gallons on your last delivery by the days since the previous fill. As a benchmark, one industry source citing the EIA puts the average household at about 750 gallons for October–March, which is roughly 4 gallons a day averaged over those six months. January and February run higher.
When to refill
One supplier advises scheduling a delivery once an underground tank gauge reaches the low 30s (percent). In cold snaps deliveries can be delayed, so order earlier or use automatic delivery.
Estimate burn rate from your appliances
Gallons per hour = appliance input (BTU per hour) ÷ 91,452. A furnace rated at 100,000 BTU per hour burns about 1.09 gallons per hour while it runs. A 40,000 BTU per hour appliance uses about 0.44, and 150,000 BTU per hour about 1.64.
What matters is how long it runs. That 100,000 BTU furnace running 10% of the day uses about 2.6 gallons, 25% about 6.6 gallons and 50% about 13.1 gallons. This is why typical winter use lands between 4 and 8 gallons a day, and why a cold snap can double it. Check your furnace’s input rating on its label.
Cost per day and per fill
At an example $2.78 per gallon, a 400-gallon fill costs about $1,112. At 4 gallons a day that is about $11 a day; at 8 gallons a day, about $22.
Reading the gauge
Gallons left = 500 × gauge reading. At 30% you have 150 gallons, which is 30 days at 5 gallons a day. To keep a 14-day safety margin at 8 gallons a day you need 112 gallons, or about 22%, so a refill order around 30% leaves time for delivery delays.
Stretching a tank
Lower thermostat settings, sealing drafts and insulating the attic cut heating demand. Keep the furnace and filters serviced. If you smell gas, leave the building and call your supplier or emergency services from outside.
See also the 1,000-gallon tank and propane vs firewood costs.
FAQ
How many gallons are in a 500-gallon propane tank?
About 400 usable gallons, because tanks are filled to 80% to leave room for expansion.
How much energy is that?
400 gallons × 91,452 BTU is about 36.6 million BTU.
How much does a fill cost?
About $1,100 at an example price of $2.78 per gallon. Check your local price.