To encourage conservation and cover the higher cost of buying water from MWD at a higher rate, a tiered rate system for actual units (ccf) used is in place for water usage. This system imposes higher rates on customers who use larger amounts of water. One unit (ccf) equals 748 gallons. The per-unit cost charge covers the water delivery cost. It also covers the cost of treating the water to ensure that it's safe to drink, as well as energy costs for pumping the water to customers.