Frustrated by the pending shutdown of two nuclear power plants on Lake Ontario, Gov. Andrew M. Cuomo plans to order state regulators to mandate that, by 2030, half of all power consumed by New Yorkers be generated from renewable sources that emit much less carbon dioxide, people briefed on the matter said.

Mr. Cuomo, a Democrat, has already declared a goal of having 50 percent of the state’s power come from solar, wind, hydroelectric or other renewable sources in 15 years, but the state has had no means of enforcing that directive. The governor intends to have the Public Service Commission, which regulates utilities in the state, codify the requirement, these people said. Some of them, including a Cuomo administration official, spoke on the condition of anonymity because they did not have permission to discuss the proposed mandate.

The mandate would be another step toward the governor’s goal of a 40 percent reduction in carbon emissions from plants supplying the state’s electricity. In the intervening years, the energy policy would give utilities an incentive to use power generated by nuclear plants, which are considered clean sources, though not renewable.

By pushing utilities to obtain more of the power they distribute from less-polluting sources, state officials hope to delay the planned shutdown of two nuclear power plants on the shore of Lake Ontario. Aides to the governor have been trying for several weeks to dissuade Entergy from closing one of them, the James A. FitzPatrick Nuclear Power Plant in Oswego County.