People used less electricity in Dunedin, Central Otago and the Wakatipu last month than in May 2009 as the region enjoyed a warm start to winter.
The Aurora lines network distributed 120GWh of electricity last month, 10% less than in May last year, Delta network services manager Lindsay McLennan said.
"This reflects the milder start to winter this year and that, in May '09, there were snowfalls to sea level by the middle of May," Mr McLennan said.
Dunedin had a better-than-average mean temperature (up 0.5degC to 9.8degC) and more sun (117 hours, or 117% above normal), National Institute of Water and Atmospheric Research figures for May show.