The City and County of Denver has made sustainability a core business value, making energy efficiency a priority. Through its partnership with the Better Buildings Challenge, the City has committed to reducing energy use by 20 percent by 2021 across its building portfolio, which totals more than 6 million square feet. Mayor Michael B. Hancock plans to use the City's leadership to challenge private building owners, the non-profit sector, and schools to make similar energy reductions. Denver is undertaking a number of energy savings projects within its own buildings and working with external partners to save energy and money across the city. The City of Denver is lucky to have partners such as The Alliance Center for Sustainable Colorado, whose efforts showcase the rewards of deep retrofits focused on energy efficiency.