A 2009 Executive Order that requires federal agencies to cut
their greenhouse gas (GHG) emissions will result in a 28%
overall reduction by 2020. The figure is the aggregate of
targets set by 35 federal agencies, which will comply by
increasing their use of energy efficiency and renewable
energy.

Source: http://www.eere.energy.gov/news/news_detail.cfm/news_id=15779