Energy Minister Gerry Brownlee has rejected warnings that changes to the electricity industry could raise the risk of a system failure.
The Institution of Professional Engineers made the warning in a submission to Parliament's finance and expenditure select committee on the Electricity Industry Bill on Wednesday.
It says forcing Meridian Energy to swap some of its South Island hydro stations with fellow state-owned Enterpise Genesis Energy will make the generation system more complex and undermine the security of supply.
But Meridian Energy chief executive Tim Lusk says the proposal is not as complex as it looks and he is confident the risk can be managed.
Mr Brownlee says he, too, is not concerned.