INTRODUCTION The City of Austin has considered energy efficiency for new construction an important issue since the adoption of its first building energy code@ the 1983 Model Energy Code (MEC)@ in late 1983 (Austin 2008a). Austin@ as well as all Texas municipalities@ is allowed to pursue more stringent building regulation than would exist at the state level as a result of home rule legislation. In the case of Texas@ the state did not have an energy code prior to 2001 while Austin continued to adopt@ and supplement@ updated energy codes such as the 1986@ 1989 and 1993 MEC followed by the 2000 International Energy Conservation Code (IECC) in late 2001. Although the city used the MEC as a foundation for energy efficient construction@ it incorporated more aggressive conservation features not covered in the MEC through local admendments. One such example of an Austin amendment was an effective shading coefficient (SC) for fenestration when the MEC prescriptive codes required none (CABO 1983@ 1986@ 1989). Due to the long history of energy efficiency ordinances by the city@ combined with the availability of electrical energy data from Austin Energy@ this city is well suited to examine the energy impacts resulting from the implementation of residential energy codes. It is the goal of this study leverage energy data@ along with other information@ to investigate the persistence and realization of energy impacts from refinements in the residential building energy code. It is also the intent of this paper to examine the energy impacts as a potential for improvements in residential energy efficiency across the entire population. There are several cities currently exploring options in improving home energy efficiency through ordinances or consumer education at the point of sale of an existing home. These communities considering such initiatives include San Francisco@ Seattle@ Denver@ Portland and Berkeley as well as Austin itself. Although the administrative details for these initiatives are still being fleshed out@ the question arises about the potential impact of minimum energy efficient standards. Improvements under consideration include attic insulation@ repair or replacement of duct work and installation of solar screens; predominantly the measures that form the foundation of the residential energy codes for the City of Austin.