Using GPS data logged for a representative sample of individual vehicles in private use, we assess the viability of plug-in hybrid electric vehicles (PHEVs) in Sweden for a wide range of techno-economic conditions. We determine requirements for PHEVs with the aid of a simple parameterization used to analyze the GPS data covering number of trips, driving distance per trip, and parking times, logged for 30days or longer, for 432 conventional Swedish cars. Good opportunities for charging and regular distances traveled between rechargings increase the potential for battery-powered driving and, along with a high annual mileage, enhance the viability of the PHEV. Therefore, commuters are likely to be the first drivers for whom the PHEV will be cost-effective. Making charging infrastructure available at work places would enhance the opportunity for this group of early adopters, as we show that charging while at work is comparable at the initial stage to halving the marginal battery costs for the average commuter.