Utilities cannot charge customers who produce some of their own energy more than other customers, the Kansas Supreme Court ruled Friday in a decision that strikes down proposed rates from two companies.

The state's highest court found the proposals by Westar and Kansas Gas and Electric constitute price discrimination against residential customers who use solar panels or windmills to generate some or all of their electricity.

The opinion, written by Justice Caleb Stegall, said such price discrimination undermines the policy preferences of the Legislature. It notes lawmakers codified into state law the goal of incentivizing renewable energy production by private parties.

Calling the utility companies' proposal unlawful, the state Supreme Court reversed a lower appeals court ruling that had upheld it and ruled the Kansas Corporation Commission erred in approving the discriminatory rate. It sent the matter back to the commission for further proceedings.