As part of a package of subsidies aiming to increase sustainable use of energy in tertiary sector buildings, the Brussels government offers financial assistance for building owners seeking to install renewable energy systems. The subsidy covers 40% of the investment cost in the renewable energy system, including studies. Renewable sources covered include: hydropower; solar energy (hot water and electricity); geothermal; biogas; waste gases (including agriculture and forestry); renewable energy using boilers; central heating systems using cogeneration. Small wind power systems are excluded, as are heat pumps are covered only under specific conditions (there must be a net gain in primary energy supply of the building; pumps using outside air are not covered). Photovoltaic panels used for water heating must be accompanied by an energy efficiency monitoring system for two years. The installed system must directly meet the buildings energy needs.