Why don’t the Gallons Delivered equal what the Gauge Showed?

There are many reasons why the gallons delivered didn’t equal the amount you expected if you are calculating the expected delivery by the starting and ending percentage on the gauge.

Tank Gauges and Their Accuracy

Propane tank float gauges, which are the most common type of mechanical level indicator, are relatively basic and not highly precise. Their accuracy typically ranges from ±5% to ±10% of full scale, depending on factors like tank size, float condition, and installation quality.

• Best-case accuracy: Around ±5% when the float mechanism is in good condition and the tank is on level ground.
• Common real-world accuracy: Often ±10% or more due to mechanical wear, sloshing of the liquid, or the tank being off-level.
• Low readings less accurate: Float gauges are especially unreliable at very low tank levels (below ~10%) due to the angle and position of the float arm.

While float gauges are useful to gauge an approximate tank level, they are not ideal for precise measurement.

Using the Monitor Reading

If you are going by the monitor reading there are a few things to factor in. The monitor is reading the dial on the tank which is tied to the float gauge. The float gauge as explained above can have an error rate of 5-10% which yields the same error on the monitor reading.

Also, you need to consider when was the last reading reported? If the reading was not just before the tank was filled you may have used some gas in between the time the monitor reported and the tank was filled.

Temperature Effects

Temperature doesn’t change the total energy you’re buying (thanks to compensation), but it can affect how full your tank appears. Temperature has a significant impact on the gallons of propane delivered into your tank because propane, like most liquids, expands when it warms up and contracts when it cools down. Here’s how that affects delivery:

1. Propane is sold by volume (gallons), but it changes with temperature

• Warmer propane expands, so you get fewer pounds (or BTUs) of energy per gallon.
• Colder propane is denser, so you get more actual energy per gallon, even though the volume may appear the same.

2. Standard delivery is temperature-compensated

• In the U.S., propane deliveries are legally required to be temperature-compensated to 60°F (15.6°C).
• This means the metering system adjusts the gallons delivered so that, no matter the outside temperature, you’re billed as if the propane were at 60°F — ensuring fairness and consistency.

3. Impact on how full your tank appears

• If your tank is filled on a cold day, the propane is denser, and as it warms up later, it will expand — possibly making the tank report a higher reading on the gauge.
• If it’s filled on a hot day, the propane is already expanded, and as it cools, the volume contracts — making your tank gauge show a lower reading even though you received the correct amount.

Was the Tank Below 7% before Filling?

If your tank was showing 10% or less, the actual level in the tank maybe much lower or even empty. When a tank is below 10%, the gauge and/or monitor reading may not be accurate at all and the tank could be empty or close to empty.

Float Could be Stuck

If we filled your tank and it isn’t reading around 80%, your float gauge maybe stuck. When we fill we necessarily don’t fill till the gauge says it’s full, but use the bleeder valve which is a more accurate way to know the tank is full. If the gauge is stuck, you may have more gas than the gauge is reporting.

How Propane Depot Calculates the Gallons Delivered

Propane Depot has sophisticated delivery software and systems in place to eliminate the chance of errors in deliveries. First, to make a delivery the driver has to be on your delivery ticket on the trucks tablet. If they aren’t located at the address of the ticket they are delivering to, the system will not let the driver start the delivery. Then, once the delivery is completed, the meter reports to the tablet in the truck the exact gallons delivered which is then transferred to our office via a cellular connection.