Accountancy firm PricewaterhouseCoopers last week published its annual compendium of lines companies' information disclosures, the first since Auckland-based Vector and New Plymouth-headquartered Powerco bought the assets of UnitedNetworks.

Vector won the United Auckland and Wellington electricity networks, while Powerco picked up the Thames-Coromandel area and some central North Island electricity assets, as well as some Wellington gas pipelines.

Vector, this country's largest lines company, was down the profitability table, with a net profit of 0.4 cents per kWh, while second largest Powerco was placed runner-up in the PWC profitability measures, with an after-tax profit of 1.5 cents.

Both companies' charges were below the industry average, though Powerco's were higher than Vector's.

The best performing was Westpower, which operates on the South Island's West Coast. It earned 2.6 cents per kWh.

Marlborough Lines, a community trust-owned company with less than 36,000 customers, earned an 18.3 per cent return, the highest in New Zealand. The worst performer was Network Waitaki, which earned a 0.4 per cent return.

Electricity Networks Association chief executive Alan Jenkins said many smaller, trust-owned lines companies would not be economic in any other ownership structure.