Many utility and government programs exist to promote energy efficiency (EE) in residential buildings. While programs have succeeded in reducing per square foot energy usage intensity (EUI), they do not necessarily promote conservation, in terms of reduced total energy consumption. Using statistical analysis and data mining techniques, we examined relationships between home size, electricity and natural gas EUIs, and neighborhood level socio-economic attributes among similar to 1.3 million single-family homes in Los Angeles County (LAC). We observed that among homes constructed between 1900 and 2010, the growth in median home size by construction vintage year has outpaced combined EUI reductions by 60%. Results of a Monte-Carlo sampling procedure derived from these observed trends indicate that past historical energy savings within LAC, attributable to state mandated EE policies, could have been equivalently achieved by constraining growth in the size of newly constructed homes. These findings have significant implications for the design of future energy conservation policies within growing urban areas.