Doubt is being cast over whether the family of Folele Muliaga will be able to secure compensation.
Mrs Muliaga, 45, died on 29 May 2007 after the electricity supply to her home in Mangere was disconnected, preventing the use of her oxygen machine.
Mercury Energy, the retail arm of State owned Mighty River Power, disconnected the power because of an unpaid bill of $168.40.
Coroner Gordon Matenga has found that the disconnection contributed to her death and has criticised both Mercury Energy and the Counties Manukau District Health Board for their handling of the case.
The Muliaga family now plans to sue the power company and the board.
But a lawyer, Grant Cameron, who has experience in compensation claims, says that will be hard as New Zealand law does not adequately support families in these circumstances.
The inquest was told that Mrs Muliaga died of complications arising from her morbid obesity and the disconnection contributed to her death.
It also heard there was uncertainty as to whether her family was fully informed about the seriousness of her health and her care requirements.
Family members said they did not know Mrs Muliaga's medical records stated she was not to be resuscitated if her heart stopped.
The inquest took two weeks and heard from 20 witnesses.