By 2007, 24 of the 50 US states were generating at least 1 GW of green power from non-hydro sources, notes the 2009 NREL State of the States report. Wind energy accounted for the largest percentage of nation-wide growth in generation from renewable energy sources between 2001 and 2007, including a 30% increase in 2006 and 2007.

Biomass continued to expand its power output across most regions, with states such as Delaware, Utah, Minnesota and Alaska showing the most recent growth. Biomass continued to be strong in southeastern states, including Georgia, Alabama and Florida.

As a percent of total electricity generation, non-hydro renewable energy increased 33.7% between 2001 and 2007, reaching a national total of 105 TWh. California leads the country in total non-hydroelectric generation, although Maine is top when rated to population and gross state product. Washington leads in total green power if hydroelectric resources are included.

Solar capacity is concentrated in southwestern and northeastern states, and South Dakota ranks first in overall growth in non-hydro renewable energy between 2001 and 2007, according to the key findings of the report.

Generation from geothermal in the lower 48 states is concentrated in California, Nevada and Utah, and the leading states for wind energy are Texas, California, Iowa, Minnesota and Washington, although Wyoming leads in per-capita wind generation.

The 212-page report contains 101 charts which dissect renewable energy technologies and policies, as well as an appendix of clean energy resources. While it provides state-by-state comparisons, NREL says the report is not meant to be a renewable energy scorecard.

“This is the only report that looks at data from every state and attempts to quantify the links between renewable energy development and policy implementation," says NREL analyst Joyce McLaren, who led the report team.

“It's interesting to know where and how much wind energy is being produced, but knowing that alone isn't going to help move you forward. This report tries to identify how states are moving forward and which mechanisms are the most effective and efficient."

This is the second annual State of the States report. NREL energy analysts began compiling new data and making initial comparisons last February. The project was developed by DoE, NREL and the American Council for an Energy-Efficient Economy, and is funded by the DOE’s office of Energy Efficiency & Renewable Energy.

All but 14 states have adopted renewable energy portfolio standards or goals, and all but 7 states have net-metering policies in place. Certain policies appear to work particularly well in combination, explains McLaren, noting that more renewable energy has been developed in states that require utilities both to disclose their fuel mix and offer customers the option to purchase electricity produced with renewable fuels.

States that have a renewable portfolio standard appear to be generating more clean wind energy the longer the RPS has been in effect. States that implemented net-metering legislation in 2005 had significantly more green power generation by 2007 than states without such a policy.