The growth in geothermal and wind energy is helping to reduce New Zealand's greenhouse gas emissions when dry weather depletes its hydro-generating capacity, a government report said Friday.

The New Zealand Energy Quarterly, from the Ministry of Business, Innovation and Employment (MBIE), showed that record low hydro inflows in the South Island for much of the first half of the year drove hydro generation in the June quarter to a four-year low.

Hydro generation in the South Island was 6 percent below the previous quarter and 25 percent down from the June quarter last year.

The renewable share of electricity generation, including hydro, dropped to 64 percent, the lowest since the June quarter of 2008 when renewables made up just 56 percent of generation under similar conditions.

Output from the Waitaki hydro scheme, which generated 35 percent of the country's hydro-electricity in an average quarter, dropped almost 30 percent, said the report.

Hydro output and total electricity demand in 2008 were similar to the June quarter, but increased geothermal and wind generation commissioned in the intervening years resulted in a 17-percent drop in the generation required from gas and coal in the June quarter when compared to the June quarter of 2008.

MBIE energy information and modeling team manager Bryan Field said more coal and gas still had to be burned, increasing greenhouse gas emissions to almost twice what they were for this quarter last year, but still 25 percent down from the June quarter in 2008.

"However, New Zealand continues to see the benefits of increased diversity in its renewable energy portfolio," Field said in a statement.

"New plants commissioned in the last two years meant geothermal and wind generation combined met 18 percent of New Zealand's electricity demand. During a similar dry period in 2008, they made up just 10 percent."