AES Hawaii Inc. has agreed to significantly reduce greenhouse gas emissions at its coal-fired plant in Kapolei, which provides about one-fifth of Oahu’s electricity, the company said in a statement on Wednesday.

The announcement came after the Sierra Club earlier this week sued the Hawaii Department of Health, asking a state judge to require DOH make the power plant reduce its carbon dioxide emissions as mandated by state law. In its complaint, the Sierra Club said the department had failed to fulfill a duty to make sure AES had submitted a plan to lower emissions to at least 1990 levels by Jan. 1.

The Department of Health declined to comment when asked about the complaint. But AES said it planned to lower its carbon emissions.

“AES is doing its part to help Hawai‘i achieve its green energy goals by committing to reducing CO₂  emissions by 16% compared to a decade ago,” the company said in a statement attributed to Mark Miller, chief operating officer for the AES US Generation businesses.

David Kimo Frankel, a Honolulu attorney who filed the suit for Sierra Club, said the announcement indicates the group achieved its primary goal, which was to get the Department of Health to act and for the power plant to lower its emissions. Although there still has been no official plan, Frankel said it appears one is coming soon.

“Things will probably get resolved fairly quickly,” he said.