As Nathan Kokes, Toyota's brand manager for advanced technology vehicles, told us back in April when the Prime was unveiled, giving the Prime only four seats was important for the car's overall efficiency. If the rear were to seat three across, the car would need to have more reinforcing material and its 3.3-kW charger would need to be moved. Those changes are possible, and Koji Toyoshima said he's ready to make them happen.
Toyoshima, the chief engineer for the new Prius and the Prius Prime, told AutoblogGreen during our pre-production test drive that he's looking forward to figuring out how to expand the rear seating area in the Prime. It's one of the things he's working on, alongside early, early work on the next-gen Prius, which isn't due for a few more years. Toyoshima couldn't share details on when a five-seat Prime might follow the four-seat version, but at least we know that this new Prime is not the end of the road for Toyota's electric improvements.