Nature Energy 2, 17019 (2017); published 17 February 2017; corrected 6 March 2017.

In the version of this News & Views originally published, reference 5 was incorrect. The correct reference is given below. This error has been corrected in all versions of the News & Views.

5. Toutov, A. A. et al. Nat. Energy 2, 17008 (2017).