There is a gauge on the top of the tank under the lid which shows the percent of propane remaining in the tank. If you are on our Automatic-Fill program, we use a Degree-Day system which allows us to forecast when to make a delivery. Our Delivery Representatives generally come to refill the tank when the gauge reads between 20%-30% full. Or, you may choose to have the tank filled on a Will-Call basis, meaning you monitor the tank level and call us when the gauge reads between 20%-30% full. You may also place an order online.