The share of renewable energy on the grid in New Zealand is the highest it's been in close to 20 years, the country's energy minister said Thursday.

The share of electricity generated from renewable resources last year was 79.9 percent, a 5 percent increase from the previous year.

"New Zealand's share of renewable electricity generation is the fourth largest in the world," Energy and Resources Minister Simon Bridges said in a statement.

The government attributed the rise to the growth in geothermal generation, which more than doubled in the last decade.

New Zealand last held an auction for oil and gas exploration in December, which Bridges said was the most successful to date. Around 149 million barrels of oil reserves remain in fields already in production and gas production was near 450 million cubic feet per day in 2011, the last full year for which the government has data.

In his statement Thursday, the minister said geothermal energy contributed more to the New Zealand grid than natural gas last year.

"This is a clear sign that when a government enables a market with direction and certainty, it results in real investor confidence," he said.

The government aims to have 90 percent of its electricity supplies through renewable resources by 2025.