Vodafone New Zealand boss Russell Stanners says its cable networks will be 'future-proofed' through a $22m upgrade.

Vodafone will upgrade its cable broadband networks in Wellington and Christchurch to provide gigabit download speeds, at a cost of $22 million.

The speeds are 10 times faster than the highest speeds now available on the networks and match the fastest "Gigatown" home broadband plans being offered in Dunedin over the government-backed fibre-optic ultrafast broadband network.

Vodafone chief executive Russell Stanners said it would upgrade the networks progressively, with the first customers getting the option of the speed hike from the middle of next year.

Its gigabit cable broadband service would be "affordable", but further information on customer plans and pricing would not be available until next year, Vodafone said in a statement.

The company acquired the networks in 2012 through its purchase of TelstraClear.

Vodafone would be one of the first operators in the world to upgrade its cable networks to a new technology standard, DOCSIS 3.1, Stanners said. The upgrade, which would increase the overall capacity as well the speed of the network, will be carried out with the help of Chinese technology partner Huawei, he said.

Spokeswoman Elissa Downey said the upload speeds would also not be announced until next year. But an Australian government report suggests upload speeds of 100 megabits per second are achievable using the technology.