Alternative energy sources, such as wind, biomass and geothermal, are far more widely deployed than solar power, largely because solar can be prohibitively expensive. But that may be about to change for 40 Berkeley, Calif., residents. The Berkeley city council recently created a new tax district that residents can join to finance solar energy systems through their property taxes. Berkeley FIRST is intended to solve many of the financial hurdles facing property owners who want to install solar systems. Under the program, homeowners will be able to borrow money from the city's Sustainable Energy Financing District to install solar photovoltaic electric systems and then pay back the loan at a fixed rate over 20 years. One advantage of the program is that the tax will stay with the house if the homeowner sells. On a typical $22,000 solar energy system, residents would pay about $180 a month, based on a 6.75 interest rate, after state and federal rebates are issued. A calculator is available on the Web site to help homeowners compute the cost benefit of the program for their households. Initially, Berkeley FIRST will only fund about 40 installations and provide up to $37,500 per installation. If the program can be sustained, it will be offered again next year. Agencies in San Francisco, Santa Cruz County, Boulder, Colo., and the state of Colorado are also considering establishing solar financial districts based on Berkeley's model.