There has been steady progress on the science and engineering behind nuclear fusion energy, but a demonstration plant is still likely to be 20 years away, Kimberly Budil, director of the Lawrence Livermore National Laboratory (LLNL), told MIT Technology Review.

“Some startups are making bolder claims than that, predicting a decade or less, “but I think the challenges are much more significant than people realised at the beginning,” Budil said. “Plasmas are really complicated.”