Propane is temperature dependent: the volume of propane in a tank rises and decreases with temperature. This means that propane expands with higher temperatures and becomes denser if they fall.
Propane volume decreases in winter
Propane users tend to get confused in winter: as propane is delivered into their tank, they notice that the level is slightly lower than expected. For example, if 200 gallons has been delivered into a 500-gallon tank on a particularly cold day it is likely that the propane tank gauge will read less than 40% (if the tank was empty originally). The reverse is also true for higher temperatures. This does not mean that there is less propane in the tank: at any temperature there remains 848 pounds of propane (4.24 lbs per gallon). Therefore, the amount of energy remains the same.
Automatic pressure compensators
Regulations exist at federal and state level to protect the consumer. The truck that delivers propane into your home has to be equipped with an automatic temperature compensator (for volume correction). During the propane delivery, this device checks the temperature of liquid propane and ensures the customer is getting the amount they ordered automatically. Automatic temperature compensators are configured to the temperature at the time of delivery so that the amount of propane a customer has ordered is the volume as the amount of propane they will have in their tank after delivery.