MONTPELIER (AP) - The state of Vermont is narrowing its suggestions about how to meet its long-term goal of getting 90 percent of the state's energy from renewable sources by mid-century.

On Monday the Department of Public Service outlined a progress report on its "Total Energy Study" that is designed to lay out by next summer how to reach the goal of 90 percent renewables by 2050.

Among the options being considered are "creation of an economy-wide carbon tax," requiring all energy providers to meet a fraction of their sales with renewable energy or energy efficiency and ensuring project have needed financing.

Director of Energy Policy Asa Hopkins said that until now the conversation about reaching the goal has been largely been "without a frame or structure."