The U.S. Department of Energy’s National Renewable Energy Laboratory (NREL) issued a report that shows the fuel economy benefits of hybrid electric diesel delivery vans when compared with similar conventionally powered vans. The report is titled Eighteen-Month Final Evaluation of UPS Second Generation Diesel Hybrid Electric Delivery Vans.

NREL evaluated fuel economy, maintenance and other data from 11 hybrid and 11 conventional step vans operated by UPS in Minneapolis. NREL Project Engineer Michael Lammert said that during the on-road part of the organization’s study, it found the hybrid vans achieved 13-20% better fuel economy.

During dynamometer testing, NREL put the vans through three standard drive cycled to simulate a range of delivery routes. The hybrid vans showed a 13-36% improvement in fuel economy, and up to a 45% improvement in ton-miles-per-gallon.

According to NREL, the hybrid vans utilize 44 kW electric motors, lithium-ion batteries, and regenerative braking. The vans operated by UPS were the same age and ran under similar conditions. The two groups of vans switched route assignments during the study so NREL could see how the vans operated on the same routes.

NREL stated it has been working with UPS for five years to track and evaluate the company’s hybrid vehicle performance. NREL performed its first study on first-generation hybrid vans operated by UPS in Phoenix in 2008. In 2010, UPS deployed 200 second-generation hybrid vans in eight U.S. cities, including the 11 evaluated in the recent study in Minneapolis. The second-generation vehicles feature “engine off at idle” technology that automatically stops and restarts the engine during brief stops.

You can read the NREL report here.