Hansen said Unison's tariff was not as cost-reflective as it could be, but it did not breach the code.
"Unison has informed us that its new pricing is an interim step towards our preferred approaches, as it considers it is currently constrained by incomplete roll-out of smart meters and limitations in retailers' billing systems, which are necessary requirements for service-based prices," he said.
Visiting Hawke's Bay last night, Green Party co-leader James Shaw said the authority had been captured by partners of the industry who were dealing with changes in the energy market in a defensive way.
"In any decision up for change, entrenched companies dig in and say they're not going to change. Companies that can adapt come out in front," Shaw said.
He said such charges discouraged those who wanted to switch to solar, when people should be encouraged to change.
Greenpeace climate campaigner Simon Boxer said Unison's charge put a tax on solar.
"This is a blatant move by the authority to wash its hands of protecting and promoting renewable energy like solar so that it can continue to massage New Zealand's electricity monopoly."
Unison general manager of business assurance Nathan Strong said it was pleased the Electricity Authority acknowledged there was no difference between a customer with solar panels and the average customer "in terms of their reliance on our network to supply them with electricity at peak times and in winter, regardless of how much electricity is used overall".
"Those customers who can't afford or are unable to install solar shouldn't have to carry the cost of the network being available to those who do.