Unions and the Greens have condemned the latest part of NSW's power sell-off after New Zealand firm Trustpower snapped up five state-owned renewable energy generators for $A72.2 million.

The NZX-listed, Tauranga-based company is buying Hume hydro power station on the Murray River, the Burrinjuck hydro power station in southwest NSW and the Keepit hydro power station, northwest of Tamworth.

It's also purchasing Blayney wind farm, west of Bathurst and 80 per cent of the Crookwell wind farm in the southern tablelands.

The generators are owned by the state government's Green State Power corporation, which also operates a hydro power station at Brown Mountain in southern NSW and a 1614-hectare carbon offset tree plantation.

Treasurer Andrew Constance said proceeds from the sale, which was listed in December and is expected to be completed in July, will be spent on infrastructure.