Transpower's received draft approval for a 193-million-dollar upgrade to the upper South Island power grid

The Commerce Commission's green lit the investment - to ensure it can meet rapidly growing demand in large parts of the South Island into the 2030s.

It will let areas north of Twizel access reliable, lower-cost power, generated by major hydro schemes in the southwest.

Grid Development Executive General Manager, Matt Webb, says demand's risen consistently in recent years - and this will accelerate as homes and businesses switch to electricity.