NBN Co has claimed that the operating cost of powering up to 60,000 nodes across Australia each year will run at a far lower cost than the up-front capital cost of rolling out fibre to the premises (FttP).

As part of NBN Co's move to a multi-technology mix model for the National Broadband Network (NBN), the company and Telstra are trialling fibre-to-the-node technology across a number of states in Australia ahead of an expected wider rollout of the technology next year.

One of the major criticisms of going with fibre to the node instead of fibre to the premises is the cost of powering each of the nodes that are planned to service 384 premises each.

NBN Co's strategic review did not forecast the cost for powering the nodes in the current trials under way, but in answers to questions on notice from the July NBN committee hearing, the company indicated that its own working assumption is around AU$2,000 per node, per year.

This would put the annual cost of powering the nodes at AU$120 million, if the company reaches the 60,000 figure outlined in the Coalition's 2013 broadband policy.

Despite the high cost, NBN Co indicated that this would be cheaper than the capital cost of constructing out fibre to each premises.

"Each node services hundreds of premises, so the node electricity cost on a per-premises basis is very small, relative to the cost of extending fibre to each premises," the company said.

The average power consumption per node would be 6,709kWh per annum, NBN Co said. The batteries to power the nodes in the event of a power outage will cost AU$3,000 per node. Each battery has a life of 15 years, and can run VDSL with vectoring for up to six hours in the event of a power outage for 192 premises, NBN Co said.

NBN Co also, for the first time, detailed some of the costs for conducting the fibre-to-the-node trials. The initial trial of 10 nodes in Umina, and one node in Woy Woy, cost AU$1.4 million for design, construction, and equipment costs.

NBN Co's fibre-to-the-basement trial at eight sites in Carlton, Victoria, cost the company AU$765,000. This included a cost for VDSL equipment at around AU$40,000 per unit.

The company won't know exactly how many premises will be getting fibre to the node until NBN Co finishes negotiating with Telstra and begins a wider rollout.

NBN Co said in the response to questions on notice that although the NBN Co Strategic Review recommends a rollout of 24 percent FttP, 41 percent FttP/B, and 28 percent hybrid fibre-coaxial (HFC), this is just "preliminary", and not the final indication for technology to be used by the company.

Another criticism of fibre to the node is that NBN Co will be unable to upgrade single premises to fibre if the copper line to that premises isn't capable of achieving a minimum 25Mbps speed, with claims that a whole area would need to be upgraded.

NBN Co said that the cabinets the company would use would allow fibre upgrades for premises that require or request a fibre upgrade.

"FttN cabinets can be used to deliver fibre on demand. Fibre counts have been allocated in the NBN Co fibre distribution network architecture to support fibre on demand," NBN Co said.

"The NBN Co distribution fibre architecture supports both FttN and FttP deployments, including an upgrade path from FttN to FttP."

In areas where there are more premises than a single node can handle, NBN Co indicated that it is planning to use fibre to the basement where cost effective, and small VDSL2 nodes further into the field to reduce the number of premises per node.