Local governments are increasingly taking initiatives to reduce greenhouse gas (GHG) emissions. However, limited and inconsistent data makes evaluating the aggregate impact of relevant actions difficult. This paper focuses specifically on U.S. city governments' use of renewable electricity to power their own operations. It develops a range of rough estimates for the cumulative nationwide impact of this activity and finds that it results in an annual abatement of between 5.8 and 29.2 million metric tons of carbon dioxide equivalent (CO(2)e), with the best approximation being 6.2 million tons CO(2)e a year. This is about 20% of the estimated total that could be reduced if city governments used only renewable electricity to power their operations. Despite the considerable potential that remains untapped, even the maximum direct impact resulting from local government renewable electricity use is roughly estimated as less than 0.5% of total annual U.S. GHG emissions. Government procurement policies and "leading by example" provide opportunity for additional indirect impact. (C) 2012 Elsevier Ltd. All rights reserved.