System, methods, and other embodiments described herein relate to adjusting a trip fare according to in-vehicle charging provided by a passenger. In one embodiment, a method includes, in response to initiating a trip in the vehicle for a passenger, accumulating the trip fare as a function of traveling a route to fulfill the trip. The method includes metering one or more charging devices to identify a metered charge produced by the passenger operating the one or more charging devices during the trip. The method includes computing a fare offset according to at least the metered charge to identify an amount by which the trip fare is to be discounted. The method includes adjusting the trip fare according to the fare offset to account for an electric charge provided to the vehicle during the trip.