Just over 100 customers were reconnected by 1pm, with power restored to the remaining 107 customers by 9.30pm.
Repairs are ongoing.
A Fire Emergency New Zealand spokesperson said the lines caused a small fire on the grass next to the road but not on the car.
Two Whanganui Fire Station crews and a support truck were deployed to the scene.
Due to the fire and the live wires, the two people in the car stayed put until crews had the fire extinguished and Powerco had isolated the power supply away from the downed wires.
Once the people were extricated from the car and taken to hospital, the fire crews stayed on-site to assist with traffic and scene safety while the lines were repaired.
Crews left the scene about two hours after they arrived.
Police said the vehicle was removed from the scene and roads were reopened by around 3pm.
Inquiries to determine the circumstances of the crash are ongoing.