Boulder Colorado\u2019s carbon fee on electricity is estimated to increase residents\u2019 utility bills by $16 per year and businesses\u2019 by about $45. The measure sunsets in 2012. Jonathan Koehn, Boulder\u2019s environmental manager, said the ballot measure gave city officials the option of increasing the fee if needed to get further carbon emission cuts \u201cto meet the increasing challenge of climate change.\u201d It also allows the revenue to be used for other approved carbon reduction measures, such as those to slash energy use at peak times On April 8, the environmental office will be asking the Boulder City Council to allow a tax increase and the dedication of some of the tax revenue to a demand side management program. The carbon fee, based on kilowatt hours used, is complemented by the state\u2019s renewable portfolio standard and stringent energy efficiency building standards. Colorado requires that one-fifth of electricity supplies be renewable by 2020. California requires that 20 percent of the generated electricity be renewable by 2010. In addition, there are both Colorado state and city rebates for residents and businesses that install solar and wind energy systems, which are in addition to the federal production tax credit to lighten the city\u2019s carbon footprint.