Traffic was down to one lane for most of the day until two cranes were used to pull the truck and trailer back onto the highway, which temporarily closed the road about 3.30pm.
Holden said after initial investigations it appeared the trailer unit had gone into loose gravel by the fog line and then had gone in the ditch, pulling the truck unit over.
North power spokesman Steve Macmillan confirmed the Northpower worker was the first on the scene and was able to help the truck driver. Power was knocked out to 215 customers in the area but they were back on at just after 3pm in time for milking.
A power pole was replaced.
"The Northpower worker did the right thing until the area was made safe and there was no risk of electrocution," Macmillan said.