This paper quantifies the relative cost-savings of utilizing a greenhouse gas emissions-weighted Clean Energy Standard (CES) in comparison to a Renewable Portfolio Standard (RPS). Using a bottom-up electricity sector model for Hawaii, this paper demonstrates that a policy that gives "clean energy" credit to electricity technologies based on their cardinal ranking of lifecycle GHG emissions, normalizing the highest-emitting unit to zero credit, can reduce the costs of emissions abatement by up to 90% in comparison to a typical RPS. A GHG emissions-weighted CES provides incentive to not only pursue renewable sources of electricity, but also promotes fuel-switching among fossil fuels and improved generation efficiencies at fossil-fired units. CES is found to be particularly cost-effective when projected fossil fuel prices are relatively low. (C) 2012 Elsevier Ltd. All rights reserved.