State owned Genesis Energy's share of the Kupe oil and gas field has pushed its half year profits up by 125 per cent.

Vector profits for the first half of the financial year rose 6.9 per cent, despite revenue growth of just 0.8 per cent.

Profits for the first half of the year have slumped at Contact Energy, the stock exchange's largest energy company.

Solid Energy has posted a 56 per cent jump in first-half profit on record sales while warning earnings in the second half will be "substantially" down.

Mercury Energy is raising its power prices by 5.8pc, blaming charges from the national grid operator Transpower.