Vodafone is touting hassle-free upgrades as a big reason for customers to stick with its cable network service.

﻿Vodafone cable broadband customers in Wellington and Christchurch will probably stick with the service now they can get gigabit broadband, says the head of an independent broadband comparison site.

Vodafone announced on Thursday that most cable broadband customers could upgrade their internet plans to get gigabit download speeds, following a $22 million network upgrade.

At $110 per month for unlimited data, Vodafone's gigabit cable service provides customers in the two cities with a slightly cheaper alternative to getting gigabit broadband through the government-backed ultrafast broadband (UFB) network.

UFB gigabit plans retail from upwards of about $115 but more typically cost $130 to $140.

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Gavin Male, chief executive of comparison service Broadband Compare, said the upgrade appeared designed to stop customers defecting from cable to UFB and would probably achieve that goal – especially given the $110 plan price.

UFB upload speeds should still be superior but that probably wouldn't be enough to persuade many customers to shift, he said.

"Putting myself in the consumer's shoes if I already have cable coming into my property and then I can get gig speeds on it at a good price, you wouldn't look to move."

Vodafone acquired its cable broadband networks – which it has rebranded FibreX – through its 2012 purchase of TelstraClear. The highest download speeds available had been 100 megabits per second (Mbps).

The company first announced the gigabit upgrade plan a year ago and had originally expected to start offering the faster speeds from the middle of this year.

Vodafone consumer director Matt Williams said 70 per cent of customers could get the new service now, and the remainder should have it as an option by the end of the year.

Internet providers, including Vodafone, have been able to sell gigabit plans on the UFB networks built in Wellington and Christchurch by Chorus and Enable since the start of the month.

FibreX is based on a technology popular in the United States and in Australian cities called hybrid fibre-coax (HFC). It is widely regarded as generally superior to standard copper broadband but does not provide fibre-optic cabling all the way to the home.

It also supports cable television, including Vodafone's "triple play" Sky TV cable bundle.

Vodafone's technology upgrade moves FibreX to the latest version of HFC technology, called Docsis 3.1.

Chorus quotes an upload speed of "up to 500Mbps" for its gigabit service.

Vodafone said that in "really good conditions" it would expect its gigabit FibreX plans to offer a real-world performance of 700-900Mbps down and 90-95Mbps up.

But Vodafone is promising that FibreX should be relatively painless to order, which has not always been the case with UFB.

An annual report from the Telecommunications Disputes Resolution scheme said this month that delays getting UFB had been a significant contributor to the 2619 complaints it had fielded from the public over the year to June.

Vodafone said that if it was unable to upgrade existing FibreX customers to its gigabit service within three days, then it would give them a $100 credit.

Spokeswoman Elissa Downey said capacity and congestion would "not be a problem".

"The DOCSIS 3.1 technology is fully scalable at the node – meaning we can add more capacity as we go to ensure customers always get a speed experience as described," she said.