DENVER — Out of all the states in the nation, Colorado offers the best sneak peek at what the nation will look like once President Barack Obama's energy regulations take effect.

Ten years ago Colorado became the first state with a voter-approved renewable energy standard. Larger utilities must get 30 percent of their energy from renewable sources by 2020.

The law has forced energy producers to switch from coal to natural gas, and the transition has been relatively smooth. But critics warn economic impacts remain to be felt.

Currently, Colorado has 12 coal plants and gets almost 66 percent of its electricity from coal-fired power plants.

The Obama administration unveiled a plan Monday aimed at cutting carbon dioxide emissions from power plants by nearly a third over the next 15 years.