Arizona regulators will vote this week on whether to officially begin the process to repeal renewable energy standards for many of the state’s electric utilities that were first adopted 19 years ago.

Last year, the Arizona Corporation Commission took the first steps to repeal the Renewable Energy Standard and Tariff, or REST, rules. The rules require many utility companies to obtain at least 15% of their electricity from renewable sources, with 30% of that coming from sources like residential rooftop solar panels.