Time-fill: Time-fill stations are used primarily by fleets and work best for vehicles with large tanks that refuel at a central location every night. Time-fill stations can also work well for small applications, such as a fueling appliance at a driver's home. At a time-fill station, a fuel line from a utility delivers fuel at a low pressure to a compressor on site. Unlike fast-fill stations, vehicles at time-fill stations are generally filled directly from the compressor, not from fuel stored in tanks. The size of the compressor needed depends on the size of the fleet. Although there is a small buffer storage tank, its purpose is not to fill vehicles, but to keep the compressor from turning off and on unnecessarily—wasting electricity and causing undue wear and tear on the compressor. The storage tanks are sometimes used to "top off" vehicle tanks during the day.
Time-fill stations are carefully architected based on the application they will be used for. For example, a transit bus company may need a larger compressor that can deliver 8 to 9 gallons per minute, while a refuse truck company can make due filling trucks at 3 gallons per minute using a smaller compressor. A consumer application may need far less—such as, less than half of a gallon an hour. These differences account for the large variance in the cost of installation.