You can watch Marin's news conference by clicking on the image inside this story, starting at 1 p.m. ET.
Marin started to investigate complaints about unexpectedly high bills, no bills for months at a time and multiple bills for the same time period.
He said Hydro One ranks the highest in number of complaints of any organization he’s ever seen.
In one year, he said he'd registered 9,800 complaints about the utility.
Today, Marin will give an update on the investigation, although it’s not clear what that may be.
As for customer complaints, some remain unresolved.
Lillian Woodcock, who is 90 years old and owns a cottage north of Englehart, said the heating bill for that property has tripled in a few years.
She said she called the utility and wasn’t happy with the response.
“They didn’t give me an explanation but that they’d be in touch with me,” she said.
She added she also got a letter stating someone from the utility would contact her, but said she didn’t hear from them after that.
"I did get the one answer, well what did you expect, it’s only a summer cottage,” she said.
“So outside of that, I kind of gave up.”
Hydro One said it has implemented a promise to resolve customer complaints within 10 days, but can’t speak about individual customers.
The utility also said it has improved service in the past year by hiring more people in its call centre and increasing training.
The Ombudsman’s update will be live-streamed online at 1 p.m. this afternoon.