Transpower is the national grid operator. It takes a whole-of-industry view of the electricity sector and operates the system on behalf of NZers.
I work on the system operator side, which operates assets but doesn't build anything, so I'm less aware of how they consider sustainability on the grid. But they do have environmental targets that they track each monthly briefing. They do their best to reduce waste during construction, and they have implemented strategies to reduce impact of infrastructure on the land as much as possible. We are also a big part of the push to an increasingly electrified economy.