In all but the most carbon-intensive grids, electric buses produce lower well-to-wheel carbon emissions than their diesel counterparts. The drivetrain energy efficiency is up to 500% higher than that of a diesel engine. They are quieter and produce lower levels of harmful urban pollutants (NOx and fine particulates). For governments aiming to reach greenhouse gas emissions targets in the transport sector in the next 10-15 years, the transition to electric bus fleets must begin now because buses remain in service for about 12 years.