Snap Internet, which is believed to be the country's fifth largest internet provider, is the latest to ratchet up its data caps, launching a 1 terabyte plan costing $145 a month, with a phone line included.

The monthly data cap is equivalent to the storage capacity of about 20 Bluray disks or the entire hard drive capacity on most new mid-range computers.

Marketing manager James Koers said customers who were signing up to Snap's ultrafast broadband (UFB) plans and those using the latest copper-based technology, VDSL, were demanding larger data caps. The number of customers Snap had connected to the fibre-based UFB network was now in the "low hundreds" he said.

Koers said people would need to be watching a lot of streaming video to eat through 1Tb of data. People sharing flats and homes with teenagers tended to have the largest demand.

The Christchurch-based national provider previously offered a top cap of 550 gigabytes. Koers said he personally used about 20Gb a month.

Telecom began offering a broadband plan with 500Gb of data costing $119 or $129 last month - depending where customers live. Callplus and Orcon have both launched plans with "unlimited" data at $111 and $99 a month respectively, though with some strings attached.