He was checked by his mother at 2am. Mr Haaima said he was woken by his wife who shouted that the power was off.
"I ran into Wayne's room and tried to raise him by shaking him and yelling out to him, but he was cold to the touch so I knew he was gone," he said.
"The alarm on Wayne's Bi-PAP machine was still going. Wayne's mask was still in the correct position and there was nothing untoward in the room."
Coroner David Crerar quoted Mr Haaima's doctor, Don McKirdy, who said: "Wayne died peacefully in his sleep and was unlikely to have been aware."
The outage occurred soon after 3am. An electronic alarm in the PowerNet control room in Invercargill indicated that 967 customers in the Palmerston area were without power.
Two Otago Power Services contractors were dispatched to the Palmerston substation and found that two 33KV fuses on two transformers had failed, due to possible damage from what was described as "airborne debris".
Power was restored to all customers at 4.28am.
PowerNet general manager of network operations Gary Pritchard said there were no industry protocols for power distributors to advise medically dependent customers of unplanned power outages after they had occurred.
"If PowerNet is made aware of customers that require power for medical purposes then it may, depending on circumstances, make efforts to contact the customer at the earliest opportunity," he said.
"In this specific instance, PowerNet was not aware that this customer required power for medical purposes."
Mr Pritchard said the company relied on retailers to pass on information about customers who are medically dependent on their electricity supply. Its last notification came on June 14, 2007.
Coroner Crerar asked Mr Pritchard what action PowerNet had taken to warn special clients on the night of Mr Haaima's death. The answer was none.
Reading from a letter written by his wife, Mr Haaima said she and her husband wanted manufacturers of Bi-PAP machine to introduce battery back-up systems in case power failed.
"We would like to be informed on the progress in this matter if possible, and we are willing to assist in any way," she wrote.
The couple said their son was an "amazing young man who never complained or moaned about his situation".
"Wayne had a mind like a steel trap and a sense of humour to match; he also had an opinion on anything and everything and knew how to get his point across."
Mrs Haaima said Wayne's passing had left a huge gap in their lives and he was much loved and very much missed.
In May 2007 Auckland woman Folole Muliaga, 44, died after the electricity to her Mangere home was cut off because of unpaid power bills. Mrs Muliaga used an oxygen machine.
Mercury Energy changed its rules so they could identify customers who are medically dependent on their electricity supply in the event of an outage.