The government is being urged to move more quickly to pull together a national energy strategy.
The parliamentary commissioner for the environment has written to the energy minister, saying finalising a strategy by the end of next year was too late.
Simon Upton said there were already too many large energy proposals with competing claims on the table, including turning Lake Onslow into a 'battery', which would cost billions, or developing green hydrogen.
"I really wanted to say to the government, make sure you get on with this strategy and do it in a way which ensures the public can understand the tradeoffs and consequences that are being made that they will have to live with," Upton said on Tuesday, releasing a 10-page letter to Energy and Resources Minister Megan Woods.
"New Zealand is on the cusp of the greatest energy system transformation for generations," he wrote to her in December.
It was a good strategy in planning, he said, but "an unnecessarily drawn-out process that risks being overtaken by decisions and actions taken in the meantime".
"I am concerned that decisions taken by private and public agents over the next couple of years prior to the publication of the energy strategy could commit New Zealand to suboptimal outcomes."
Wide-ranging debate involving the whole energy sector was vital to get to a low-carbon, secure and affordable system, he said.
The big issues that demanded strategic thinking included more electric vehicles, more solar and wind generation, what to do about natural gas, biofuel use, short-haul and the Tiwai Point Aluminium Smelter.
Lake Onslow showed up how the debate might go in the absence of a strategy.
"The examination of Onslow by the government has caused a range of players to expend rather a lot of energy trying to cast doubt on its worth," Upton wrote, pinpointing electricity generator-retailers in particular.
Contact Energy, for one, has warned the costs of Onslow have been vastly underestimated.
The Onslow idea was to pump water into the lake to act as back-up for hydro generation when demand was high.
But the proposal had potential on its own to reduce system-wide risks during dry years in a way other options could not, so deserved wider debate, Upton said.
Woods has not yet replied to the letter, sent several weeks ago, the commissioner said.
RNZ has approached Woods for comment.