Eleven years after EPA launched its Energy Star  Homes program, the marketplace  for new homes has  changed—but by how much?  That’s the question we set out to  answer by assessing more than 7,000  homes in the Phoenix Home Energy  Efficiency Study. In 2004, Advanced  Energy partnered with the U.S. Environmental  Protection Agency (EPA),  Arizona Public Service (APS), Southwest  Gas, and several national home  builders to assess thousands of homes in  the Phoenix area and to compare actual  energy use data for homes built to various  efficiency standards.Through assessing  the results,we wanted to determine  how much energy the baseline and  Energy Star homes actually consumed; if  homes built to Energy Star standards  were more efficient than baseline  homes; and if the implementation of  Energy Star and other efficiency programs  in new home construction  resulted in a reduction of total energy  consumption.