ADWEC is owned by the government through ADWEA and is the single buyer of desalinated water and the single supplier of water for the distribution companies. The Abu Dhabi Transmission and Dispatch Company (TRANSCO), a public company, transports water from the desalination plants to the networks of the distribution companies. The Abu Dhabi distribution company (ADDC) sells water and electricity to approximately 216,000 customers in Abu Dhabi and its suburbs. The Al Ain distribution company does the same in Al Ain. The Abu Dhabi Sewerage Services Company is a public company in charge of sanitation. The Regulation and Supervision Bureau (RSB) for the Water and Electricity Sector in the Emirate of Abu Dhabi enforces relevant laws through licensing. It is in charge both of technical regulation and price regulation. As of January 1, 2015, UAE citizens pay 1.7 Dirham (0.46 USD) per cubic meter of water for a very generous first block of consumption, which is set at 700 liters per day for apartments and 7,000 liters per day for villas. Above these amounts, the tariff increases slightly to 1.89 Dirham (0.51 USD) per cubic meter. Previously, water was free of charge for UAE citizens. Foreign residents and commercial users were always charged for water, starting at 5.95 Dirham (USD 1.61) per cubic meter in the lowest consumption block. The introduction of water tariffs for residents aims at reducing subsidies, encourage the efficient use of water and raise awareness of the importance of reducing consumption. It was combined with a large public relations campaign, as well as advice for customers who want to save water. Even before the change in tariff, bills highlighted water usage beyond a certain level in red and showed the subsidy paid by the state. The two public distribution companies receive a government subsidy. In turn, they pay a bulk supply tariff reflecting the full economic cost to ADWEC, which in turn pays for the water received from the private IWPPs under Water and Power Purchase Agreements. Bulk supply tariffs are adjusted by the RSB every four years based on maximum allowable revenues. Investment in desalination plants is financed by the private sector through BOO contracts. Investment in water distribution and sewerage infrastructure is financed by the government through subsidies to the respective public companies. Investment in both power and water production and distribution was more than US$36 billion from 1999 to 2008. Since power and water are produced and distributed by the same companies, separate figures for investment in water infrastructure are not available.