New Zealand First has unveiled legislation to make electricity cheaper for over-65s.

The party's energy spokesman Andrew Williams has a member's bill to give SuperGold Card holders a 10 per cent discount on their winter power prices.

Mr Williams says that would cut about $100 off each household's bills from May to October.

"Senior citizens are facing a long cold winter as power companies prepare to hike electricity prices even further," he said.

"The last thing we want to see is the elderly unable to afford to heat their homes. This bill would minimise the chance of that happening."

Mr Williams' bill would result in the cheaper electricity being supplied by state-owned power companies Mighty River Power, Meridian and Genesis.

Party leader Winston Peters announced the policy before last year's election.

He also promised discounts on health and vehicle registration for SuperGold Card holders.

The card, which Mr Peters pioneered as Associate Minister for Senior Citizens in 2006, also gives holders discounts on transport, local body services and other businesses.