(AP) — The Nebraska Public Power District — the state’s largest power utility — has rejected a proposal to buy up to 200 additional megawatts of wind energy by the end of the year, drawing fierce criticism from wind energy proponents.

The utility’s board voted 6-3 Friday against the additional buy.

NPPD CEO and President Pat Pope said the utility’s plants already produce more energy than customers require, and that buying more energy now doesn’t make sense.

But environmental groups criticized the vote. The Nebraska Farmers Union says the utility missed an opportunity, because it could have locked in historically low wind energy prices for the next 20 years.

The Nebraska Sierra Club says the board shirked “its legal obligation to provide electricity at the lowest reasonable cost.”