"New Zealand is a strange country, cars drive by themselves," Mr Ostapczuk said.
A Rotorua Fire Station spokesman said the car and the building were not damaged.
"The van was parked and unattended. An electrical short caused the battery terminal to come into contact with the battery cone.
"This caused the van to move forward and roll."
Mr Ostapczuk said they would be contacting the rental company and their insurance company to change the van.
When contacted by the Rotorua Daily Post the Happy Campers company was unable to comment.
Today the trio planned to head out to Waiotapu and the Buried Village, once they got their car sorted.
Police and power company Unison also attended the scene.