Quantifying the real-world CO2 emissions and energy consumption of modern plug-in hybrid vehicles

Abstract

Plug-in Hybrid Electric Vehicles (PHEV) can be classified as low CO 2 emissions vehicles in Europe if they emit no more than 50 g/km, and are viewed as favourable transitional technology for road transport electrification. Some recent studies challenge their effectiveness in reducing CO 2 emissions in real-world conditions. This study tested four Euro 6 PHEVs, both in the laboratory and on the road, for CO 2 emissions and energy consumption. The experimental results show that PHEVs in-use CO 2 emissions can range from 0 to 6 times the official type-approval CO 2 value. The results were analysed to derive relevant operation models and emission factors and benchmark their in-use performance with respect to the officially declared consumption values. A three-dimensional CO 2 emissions model is proposed based on charge level and average trip speed or wheel energy. When considering different users' charging practices and representative real-world conditions, PHEVs in-use CO 2 emissions are 1.5–2 times the official type-approval CO 2 value. Although the real-world emissions of plug-in hybrids appear to increase compared to the official values, they generally remain lower than conventional powertrains. The single-modelling element approach presented offers a novel, robust, and simple to implement way to include PHEVs in planning exercises, emissions calculation models to support national and regional inventories, lifecycle emissions estimates, and fleet-wide emissions monitoring tools.