The Austin City Council approved the Zero Energy Homes Initiative, which means the 6,500 new homes built this year must meet higher standards. And new homeowners will pay slightly more upfront costs, although energy-efficient extras and better mortgage rates will save them money in the long run.

New homes will be about 20 percent more energy efficient this year, and those standards will increase as the building codes are rewritten and updated every two years until 2015. The homes may be 70 percent more energy efficient in 2015 than today.

This move is just a part of the Austin Climate Protection Plan unveiled in February, which hopes to set a standard for U.S. cities. The plan pledges to eliminate greenhouse gas emissions from the city by 2020, rely more on renewable power and less on coal-burning practices.