Cold-Start Energy Consumption and CO2 Emissions—A Comparative Assessment of Various Powertrains in the Context of Short-Distance Trips

The issue of CO2 emissions and energy use is particularly important during short trips, where cold starts cause higher fuel consumption and increased emissions. These conditions, common in daily commuting, make vehicle efficiency a key concern. To reduce their impact, hybrid and electric powertrains have been introduced, allowing electric-only operation that eliminates direct tailpipe emissions, although indirect emissions from electricity generation remain. Real-world data show that hybrid vehicles often consume more fuel and emit more CO2 than type-approval results indicate, mainly due to the medium battery state of charge (SOC), which forces the combustion engine to operate even over short distances. Additionally, engine thermal state and ambient temperature strongly influence energy use and emissions. This study fills a research gap by comparing vehicles with different powertrains under controlled chassis dynamometer conditions, analyzing fuel (energy) consumption and CO2 emissions over the same driving cycle at various temperatures. The results show how temperature and thermal conditions affect total energy use and emissions over time and distance. The highest consumption and emissions during short trips were recorded for the plug-in hybrid vehicle in charge-sustaining mode at −6 ± 1 °C, while the electric vehicle showed the most favorable performance.