A Republican-controlled US regulator unexpectedly rejected a Trump administration plan to assist coal-fired and nuclear power plants with subsidies.

The Federal Energy Regulatory Commission (FERC) decision deals a blow to Donald Trump's promises to restore coal as a primary source of energy in the US. 

The rejected plan would have provided a financial lifeline to an industry that has seen many bankruptcies in recent years.  These coal fired and nuclear power plants that are going out of business because of the current abundance of cheap natural gas and the plummeting cost of renewables.  The US Department of Energy says 531 coal-generating units were shuttered between 2002 and 2016, while operators announced plans to retire eight nuclear reactors.

Energy Secretary Rick Perry claimed that the loss of these antiquated units threatened the grid's ability to avoid power outages "in times of supply stress such as recent natural disasters".  But the FERC noted there was absolutely no evidence to support the specious claim.

Opposition to the Trump administration's plan drew from an unusual coalition of business and environmental groups.  And federal budget hawks said subsidizing the nation's oldest and dirtiest power plants would have costed US taxpayers more than US$10 Billion annually.