A plug-in hybrid vehicle includes a hybrid powertrain system and an energy storage device. A method for operating the hybrid powertrain system includes initially operating the hybrid powertrain system in a charge-depletion mode to reduce a state-of-charge (SOC) of an energy storage device. In response to an operator request, the hybrid powertrain system operates in an opportunity charging mode to opportunistically charge the energy storage device to increase the SOC of the energy storage device during a trip prior to achieving a minimum SOC that is associated with triggering operation in a charge sustaining mode.