Telstra's chief executive Andrew Penn said the company's HFC cables worked just fine until the NBN made "technology changes" to them and also admitted the company cannot tell customers how fast their NBN internet will be until after it is connected.

Key points: Telstra says HFC "currently delivering a great experience" for its customers, NBN changes causing "issues"

Telstra says HFC "currently delivering a great experience" for its customers, NBN changes causing "issues" CEO Andrew Penn says Telstra will soon advise the market on the financial impact of NBN HFC rollout delay

CEO Andrew Penn says Telstra will soon advise the market on the financial impact of NBN HFC rollout delay Mr Penn says 5G mobile is not a complete substitute for the NBN but will "impact it as a business"

Speaking to The Business presenter Elysse Morgan during an American Chamber of Commerce in Australia (AmCham) lunch, Mr Penn said he supported NBN Co's decision to delay its rollout on the Hybrid Fibre Coaxial (HFC) network by six to nine months while it resolves technical problems leading to internet dropouts.

However, Mr Penn emphasised that those problems were not inherent in the cable, much of which was installed by Telstra.

"That is the same cable that currently provides internet services for Telstra's customers and also for Foxtel pay TV services and for those services it is absolutely fine and delivering a great experience," he said.

"It's in the process of NBN taking it and making whatever technology changes they are making to it where they have some issues."

It is not just HFC that is causing problems for NBN Co and telcos using its network, with several internet service providers compensating customers for slower-than-advertised speeds.

Telstra's boss said his company cannot accurately tell customers how fast their speeds will be until after they are connected.

"NBN cannot advise on what the actual speed is that's available in your home until it actually gets connected," Mr Penn said.

Pressed on how Telstra would advertise speeds to customers, Mr Penn said it promised a baseline and then offered upgraded speeds at an extra cost for customers whose connection could support it.

"Because NBN cannot tell us until they actually connect a home what speed they can provide to that particular home," he explained.

5G mobile won't make the NBN 'redundant completely'

Despite the repeated problems with slower than anticipated internet speeds, dropouts and higher costs, Mr Penn said he did not expect that enough customers would abandon the NBN for mobile connections to make it redundant.

"I think you will see some customers on the fixed network decide to just go mobile only, but ultimately the laws of physics apply, and if you were to carry the same amount of data on a mobile network at a national level that is currently carried on a fixed network there would have to be such a very, very significant investment in mobile capacity," he said.

"There's no doubt that 5G and mobile will play a bigger role, my point is that it won't eliminate the NBN completely.

"It'll probably impact it as a business, because they'll probably ultimately have a smaller proportion of customers that they're serving, but it won't render it redundant completely."

As for the financial impact, Mr Penn said Telstra is still calculating the short-term cost of the latest delay in the NBN rollout and will update the market in the coming days, including whether there would be any further cut to the company's planned dividend.

"Financially, there's net-net no long term change, because this affects the timing of when we receive the various different payments but, as you can imagine, there's quite a lot of complexity in the relationship between NBN and Telstra financially," he said.