New Zealand's energy system has performed strongly against the rest of the world, but concerns remain over its energy security.
It ranks ninth equal out of 127 countries in the World Energy Council's Energy Trilemma Index, which compares how nations balance energy security, equity and sustainability.
Business NZ said the country's energy system continues to be sustainable and relatively low-carbon, and geothermal development has pushed sustainability performance.
It said although countries like Canada have more storage and countries like Sweden and Switzerland are highly sustainable, New Zealand had done a good job of balancing all three dimensions.
But its energy council executive director Tina Schirr said one worrying result in the index was the decline in New Zealand's energy security.
"It's mainly driven by things like import dependence ... oil particularly, and also the storage is getting smaller here in New Zealand on oil.
"The other thing is diversity of supply. Because we rely quite a bit on water, while this is a good thing for sustainability ... it's seen as less diverse.
"New Zealand's equity score - which includes our performance in providing affordable, wide access to energy - has been stable, although the 'affordability of electricity for residents' measure has declined over the last decade," Schirr said.
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She said more diverse energy supply is better for security.
She said this year's index result showed New Zealand continued to achieve strongly overall, but raised the question of what could be done to improve energy security in the future.