This paper investigates the economic viability of plug-in hybrid electric vehicles (PHEV) in Shanghai, China based on a real-world in-use PHEV dataset. To quantify PHEV drivers’ gross profit compared with internal combustion engine vehicle (ICEV) owners, a total cost of ownership (TCO) model is adopted taking account of vehicle retail price, tax credits, subsidies, insurance, maintenance, energy prices, and resale value. The impact of the determinants for gross profit are examined in relation to vehicle distance traveled (VDT) electrically, gasoline price, electricity price, and car-buying cost. It is found that: (1) only 10% of the deployment of PHEVs (i.e., BYD Qin) is economically viable if the benefit from a free license plate is exempt; (2) the 100-kilometer gross profit of PHEVs increases linearly with the electric driving distance, while the saving of energy cost per kilometer decreases with the total VDT; (3) PHEVs’ profit could be significantly improved by reducing the car-buying cost—a decrease of 10% in car-buying cost makes 80% of the PHEV deployment feasible; and (4) if switching the daytime charges to off-peak hours, 50% of the PHEV deployment will become feasible.