You call for a fill, the driver comes out, and when you check the gauge later it reads 80%. Maybe 78%. You were expecting something closer to ‘full.’
So what happened? Did something go wrong, or did you not get what you paid for?
Nothing went wrong. Here’s the plain-English explanation for this and a few other delivery questions we hear regularly.
80% is Full
Propane expands and contracts with temperature. A tank filled to 100% on a cold winter morning would be under dangerous pressure by a hot July afternoon. To allow safe room for that expansion, propane tanks are filled to a maximum of 80–85% capacity and the gauge itself is calibrated to reflect this, reading from empty up to around 80–85% even on a fresh fill. So when the gauge reads 80%, that is a full tank.
Expansion and Contraction
Say your tank was filled during the warmest part of the afternoon. By the next morning it reads 74% and you haven’t used any gas. You almost certainly do not have a leak.
When propane is delivered during hotter parts of the day, the gas has already expanded before it enters the tank. In the cooler overnight hours, the volume of liquid propane contracts and the gauge can show a drop of up to 5% without any usage.
If you’re seeing this and it concerns you, the simplest test is to watch the gauge over a few days of normal use. A consistent, gradual drop that tracks with your appliance use is normal. A sudden large drop or a smell of gas is when you call us.
How We Measure Our Deliveries
The dial gauge on top of your tank is useful for monitoring your fuel level day to day, but it’s not what determines how much was delivered. The pump meter on the delivery truck is calibrated by law, is far more accurate than the tank gauge, and is what you’re billed from similar to how a gas station pump works.
The gauge on your tank is accurate to roughly plus or minus 10% and can be affected by temperature and tank orientation.
What you’re billed for is what the truck meter recorded. If there’s ever a significant discrepancy that doesn’t add up, call us.
The bottom line
Propane delivery has a few mechanics that aren’t obvious if nobody’s ever explained them. We’d rather you understand exactly what’s happening than wonder about it. If something ever looks off after a delivery whether that’s a gauge reading, billing, or equipment, please give us a call.
Questions? We’re here.
- Marshfield: 417.468.2549
- Conway: 417.589.8961
- Seymour: 417.935.4100
- 24/7 Emergencies: 417.468.5668
Sources
- U.S. Department of Energy — propane volume and temperature correction
- Propane Education & Research Council (PERC) — delivery process reference
- propane101.com — tank gauge and delivery mechanics
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