This is an energy policy which aims to encourage investments in new renewable energy resources by regulating the share of renewables in power generation and requiring that a certain share of electricity generation stem from renewable energy. A renewable portfolio system relies on a market trade mechanism – a cap and trade system similar to that for carbon and thus differs to feed-in tariff. Under the renewable portfolio standards if an independent energy provider cannot provide the green energy, then the state utility has to step in to make up the deficit