Electricity prices could rise by up to $100 a year if the NSW poles and wires network is privatised, an analysis has found.

In a McKell Institute report, commissioned by union-funded Stop the Sell Off campaign, economist Stephen Koukoulas warns overhead costs could drive up prices by up to $100 annually.

Mr Koukoulas says the large physical span of the network will also lead to higher staff and servicing costs.

The report also argues the short-term gains of selling the network are outweighed by drains on the budget in the future.

NSW Premier Mike Baird had announced he will seek a mandate at the March election to privatise 49 per cent of the network and use an anticipated $13 billion from the transaction for infrastructure projects.