In 2011 Moniz, a nuclear physicist, stated that wind and solar were “poorly suited for large-scale use in the absence of an affordable way to store electricity”. He was named energy secretary in 2013.

Taking questions Tuesday at AWEA Windpower, Moniz says the point he made four years ago remains “qualitatively” true.

But, he says, the threshold at which intermittent renewables become a problem for grid stability has been “pushed out”.

“We’ve