Colorado became the first U.S. state to create a renewable portfolio standard (RPS) by ballot initiative when voters approved Amendment 37 in November 2004. The original version of Colorados RPS required utilities serving 40,000 or more customers to generate or purchase enough renewable energy to supply 10% of their retail electric sales by 2015. In March 2007, HB 1281 increased the RPS to 20% by 2020 and extended a separate renewable-energy requirement to electric cooperatives, among other changes. House Bill 1001, signed by the Governor of Colorado on March 22, 2010 further increased the RPS for investor-owned utilities (IOU) and made other changes. The previous requirement of 20% renewable energy by 2020 was accelerated and increased to 30% by 2020. Colorados RPS now requires each IOU to provide specific percentages of renewable energy and/or recycled energy. The schedule starts with 3% for year 2007, up to 30% for 2020 and beyond. In addition, Colorados RPS requires all electric cooperatives and each municipal utility serving more than 40,000 customers to provide specific percentages of renewable energy and/or recycled energy: 1% for 2008-2010, up to 10% for 2020 and beyond.