A new ruling by the Electricity Authority has revealed large customers hit by high electricity prices in March this year had little chance of avoiding them.
Genesis Energy prices surged to $20,000 a megawatt hour on 26 March - four times crisis levels and 200 times the average price nation-wide.
The spike occurred when transmission lines were down for long- scheduled maintenance, starving some northern North Island customers of normal supplies of electricity.
The Electricity Authority faulted Genesis Energy in an interim report and in a final report issued on Wednesday.
The authority says the high prices came with insufficient warning and many customers had no choice but to pay up - no matter what the cost to their businesses.
It says electricity companies in a powerful position must make sure customers know of forthcoming problems so they can take steps to minimise their cost.
An earlier ruling found the market was not working properly at the time and the Electricity Authority has upheld that ruling.
The authority found Genesis did not break the law, but recommends its prices be pared back from $20,000 to $3000, subject to more submissions.
The authority's chief executive, Carl Hansen, says the price surge was not adequately forecast. As a result, some buyers were locked in to using electricity at prices they could not afford and would never have chosen had they known.
