We analyzed the economic and environmental impacts of the Energy Efficient Qualified Improvement Property (E-QUIP) proposal, which would allow accelerated tax depreciation for energy-efficient investments in commercial and multifamily buildings. The depreciation period for building investments currently ranges from 1 to 40 years, which is often much longer than the useful lifetime of the investments concerned. E-QUIP would give building energy investments accelerated and uniform 10-year depreciation if they meet strict energy efficiency criteria. It would apply to heating and cooling equipment, lighting, controls for equipment and lighting, and building shell components installed over six years. In the main scenario, we estimated that over their lifetimes, the measures spurred by this incentive would save $15 billion in energy bills (at a cost of $5 billion each to building owners and the U.S. Treasury), eliminate carbon dioxide emissions equivalent to the tailpipe emissions of 22 million cars and light trucks for a year, and result in a net increase of 130,000 job-years (total years of employment) spread over many years.