The Government Accountability Office released a report May 2 finding that a performance-based tax credit for homeowners who invest in energy efficiency measures would more likely reduce energy consumption and emissions than a cost-based credit would, but that it would be more costly. The report, Energy Conservation and Climate Change: Factors to Consider in the Design of the Nonbusiness Energy Property Credit, suggested that homeowners would be required to pay for an energy audit to determine how much their efficiency has improved. The credit is a percentage of the costs up to $500 in 2011.