The corporate regulator says it is confident that electricity and gas lines companies can still make good profits from investing in their businesses.
The Commerce Commission has ruled these companies have to cut their profits by about $45 million a year, saying their current profits are higher than they need to be to ensure an adequate return on investment.
The decision will apply to electricity lines companies from April next year and to gas lines companies from 2017.
The commission's deputy chair, Sue Begg, said the decision gave electricity and gas lines businesses greater certainty.
The chief executive of the NZX-listed Vector, Simon Mackenzie, said the commission should be raising the amount of profits it can earn, not lowering it, but his company had not yet decided whether to appeal.