Investment in new, clean electricity supply is not happening fast enough to replace closing coal power stations and the grid build-out lags what is needed for the energy transition, the head of the Australian Energy Market Operator will warn on Tuesday.

Daniel Westerman will say that investments are also urgently needed in “firming” technologies – such as pumped hydro, batteries and gas – to fill in the gaps when renewable energy is not available, with storage needing to expand by a factor of 30 by 2050.