THE National Broadband Network has revealed its expectations a year after the network is built - and this includes 8.6 million premises activated with a revenue of $5.4 billion in 2021.

The NBN's latest blueprint offers good news and bad news for more than 200,000 Australians - the good news is you'll be getting a faster internet connection using a fibre optic backbone.

But the bad news is, you'll also have to wait another year to get it.

NBN Co chief executive Bill Morrow said the network was on track to cost $49 billion at its completion - within a range of $4 billion - but the company discovered there were fewer homes to connect than it had anticipated.

"There's a difference of 300,000 from what we had said last year," Mr Morrow said.

"And this merely is just that there are fewer homes in the country than what the databases had suggested there were."

Mr Morrow also predicted this financial year would be the network's busiest, with three million homes and businesses on its road map as the NBN reached major Australian cities.

The reduced workload would not speed up the NBN's rollout, however, as Mr Morrow said "there may be more homes" in the streets workers had yet to "walk".

The NBN's new plan also confirmed one million homes and businesses would receive an upgrade to fibre-to-the-curb technology, rather than a fibre-to-the-node connection.

The faster technology, which used a fibre optic cable connected to a pit in the footpath, was expected to deliver 100 megabit per second downloads and would mainly be used in inner-city suburbs.

But 200,000 fibre-to-the-curb premises would have to wait an extra year to be connected to the NBN, Mr Morrow said, as the connections take "longer to construct" and would not launch until next year.

The new technology would also cost more than forecast, he said, rising from an estimate of $2800 per home to $2900, and making it $600 more expensive than a fibre-to-the-node or pay-TV cable connection.

Internet Australia executive director Laurie Patton said NBN Co's decision to add more fibre-based connections represented a "reasonable middle ground" for the network, as it would be less expensive to replace its shorter copper connections in a future upgrade.

"At least it can be upgraded to full-fibre at a later time," Mr Patton said.

"When it comes to fibre-to-the-node, it's a case of ripping it out at great expense."

NBN Co estimates 3 million homes and businesses will be connected to the network by June 2018 in its "biggest year yet".

But tech expert Alex Kidman said much of its accelerated rollout could be attributed to its move into "more densely packed regional and metropolitan locations".

The NBN is due to connect 11.6 million homes to the internet in 2020.