Plug-in hybrid electric vehicles (PHEVs) use stored electrical energy from electrical grids as well as chemical energy from fuel as energy sources for propulsion and various auxiliary loads. Using their electrified powertrains, PHEVs are designed to achieve improved overall efficiency and lower emissions compared to conventional internal combustion engine vehicles (ICEVs). Real-world conditions may, however, require significant thermal management energy, lowering PHEV efficiency and increasing their tailpipe emissions. A series of on-road tests were completed in Canadian summer and winter conditions to characterize the operation of four 2018 model-year PHEVs: a minivan, an SUV, and two hatchbacks. Their respective thermal management equipment and associated control strategies are discussed in this paper. Vehicle equipment included electric air-conditioning systems, electric coolant heaters, advanced heat pump systems, and conventional heater core-based systems. The results are analyzed in terms of operation strategy, thermal management loads, tailpipe CO2 emissions, and various electric range metrics. In summertime, all vehicles were able to run all-electrically for significant distances, thanks to their electric air-conditioning systems. In wintertime, the two vehicles with electric coolant heaters immediately started their engines to boost heat production, but also used stored electrical energy to provide heat and/or propulsion. One vehicle had an advanced heat pump system, which allowed it to run all-electrically for significant portions of winter testing (albeit for shorter distances than in summer testing). The remaining test vehicle had no electrical heating capability, and thus required engine operation whenever cabin heat was needed, but blended-in electrical energy for propulsion when possible.