Fill Time: Fill time stations are primarily used by fleets and work best with vehicles with large tanks that refuel in a central location every night. At a time filling station, the fuel line from the facilities delivers compressed natural gas at low pressure to an on-site compressor. Unlike quick fill stations, vehicles at time fill stations are generally filled directly from the compressor, rather than from fuel stored in high pressure vessels. The required compressor size depends on the size of the fleet. Although there is a small buffer storage tank, its purpose is not to fill vehicles but to prevent the compressor from recirculating and running needlessly - wasting electricity and causing needless wear to the compressor. A storage tank is sometimes used to "park" the vehicle's tanks during the day. The time it takes to refuel a vehicle depends on the number of vehicles, the size of the compressor, and the amount of spool. Filling vehicles can take several minutes to several hours. The advantage of using a time filling station is that the heat of compression is lower, and this results in a fuller filling than a quick filling station can provide. Another advantage is that the fleet manager can control when the vehicles are full, such as during peak hours (such as at night) when electricity rates are lower. Time filling stations are carefully designed based on their intended use. For example, a transit bus company may need a larger compressor that can deliver 8 to 9 gallons per minute, while a waste truck company can fill trucks at 3 gallons per minute with a smaller compressor. A consumer application may require much less - such as less than a gallon per hour. These differences account for the large variance in installation cost