NBN's construction costs will blow out past the $41 billion price tag previously forecast for the infrastructure project, the company revealed today.

NBN today said its budget will likely increase by up to $15 billion, from the planned $41 billion to between $46 billion to $56 billion, likely sitting at around $49 billion.

The government's equity cap of $29.5 billion will remain in place, and will run out by June 2017. NBN will undertake debt raising from 2017 from private sector sources to make up the shortfall.

Communications and Finance ministers Malcolm Turnbull and Matthias Cormann attributed the change in the peak funding requirements to the company being, "for the first time", able to accurately account for construction costs.

"For example, in 2013 the previous management of the NBN published an actual average cost of $2200 to $2500 to connect each premises via FTTP," they wrote.

"The average cost to connect FTTP was never $2200 to $2500 – not then and not now. The average cost has been over time fairly consistent. As at 30 June, the actual cost was $3632 in direct capex and $4387 including lease costs."

Similarly, the company had previously underestimated the needs of rural and regional Australia with regards to fixed wireless and satellite, Turnbull and Cormann said.

" .. without substantial additional investment would not be able to provide services to around 200,000 premises," they said.

Capital expenditure for NBN's fiscal year 2015 came in at $3.3 billion compared to $2.5 billion in FY14 as the company funnelled more money into the build, and operating expenditure hit $1.3 billion from $1.1 billion last year.

NBN chief financial officer Stephen Rue blamed the increased expenses on the costs of switching users from the Optus and Telstra networks as well as workforce expansion.

"These costs will continue to increase with fixed-line and network growth," Rue said.

In its new three-year corporate plan, released today, NBN said construction in Tasmania and the Northern Territory will be complete by 2018.

It will have 9.1 million premises ready for services, 4.4 million activations, and will count $1.7 billion in annual revenue by FY18.

Under the new plan, around 20 percent of premises will receive FTTP - compared to 25 percent as detailed in NBN's strategic review - 38 percent will receive FTTN/B, 34 percent HFC, and 5 percent and 3 percent will be on fixed wireless and satellite respectively.

Doubling revenue, users

Total revenue for the fiscal year more than doubled, up 169 percent to $164 million from $61 million a year ago.

But the company's losses grew by 12 percent to $1.1 billion as it accelerated the network build.

The company also more than doubled the number of active end users on its network, now counting 485,615 compared to 210,628 last year.

Of that total, 399,854 are on fixed-line networks, 47,473 are on fixed wireless and 38,288 are on satellite.

Serviceable premises reached 1.2 million from 553,000 this time last year.

However, the number of satellite users was down slightly from 42,948 a year earlier, with the decrease attributed to capacity issues on the interim satellite service.

FTTN launch now "weeks away"

NBN will launch a fibre-to-the-node product for wholesale partners in "weeks", the company said today, while blaming delays on the rollout on negotiations with Telstra.

It is currently conducting trials of the technology, but recently dramatically scaled down the number of premises that would be ready for service when the FTTN product goes live next month.

NBN watcher Kenneth Tsang last week revealed just 2100 FTTN premises would be ready next month, compared to the 37,200 NBN had forecast in May.

G.fast

CEO Bill Morrow also revealed the company had starting testing G.fast and would begin trials of the technology later in the year.

G.fast promises faster connections of 500mbps on short loops. NBN Co had previously indicated plans to use vectored DSL for FTTN deployments.

NBN today said it was "highly likely" it would deploy G.fast because it saw a "degree of maturity around the world that will make good use of it in Australia".

Morrow also said the company would use DOCSIS 3.1 from the beginning for its impending HFC build.