State's Choice Act of 2014 - Requires Environmental Protection Agency (EPA) regulations issued under the Clean Air Act on greenhouse gas (GHG) emissions from an existing stationary source to give states the option to impose a carbon tax for those emissions instead of, or in conjunction with, applying a standard of performance.

Requires the carbon tax to be an excise tax: (1) on emissions of GHGs, or on a fossil fuel based on emissions of any GHG that will result from the use of the fossil fuel; (2) that is no less than 20 per metric ton of carbon dioxide equivalent in 2015; and (3) that increases in each subsequent year by no less than 4% above inflation.

Requires the EPA to: (1) evaluate a state's carbon tax in 2025 to determine whether the tax and other relevant state measures will achieve by the end of 2030 the goals of the regulation that is replaced by the tax, and (2) require the state to increase the tax if it will not achieve those goals.

Prohibits availability of the option to impose a carbon tax to states that:

• are materially undermining the effectiveness of the tax in decreasing GHG emissions through other policy changes, or
• that have not complied with any EPA requirement to increase the tax.