Telstra and Samsung will on Tuesday release Australia's first-ever phone on the new 5G technology – and already its download speeds are 12 times faster than the fastest widely available NBN plan.

The two companies showed off the new Galaxy S10 5G smartphone in Sydney on Monday, with an internet speed test hitting a peak of 1.2Gbps, or 1,200Mbps.

The NBN is theoretically capable of 1,000Mbps, but for most Australians the fastest broadband plan they can purchase is 100Mbps due to physical and commercial constraints.

This makes the latest mobile technology 12 times faster than typical NBN high-speed plan. A Telstra executive on Monday claimed that would later go up to 20 times (2Gbps) with software maturity.

Where can you use 5G?

Both Telstra and Optus are in the very early stages of rolling out 5G, so coverage is sparse. But if you're lucky enough to have 5G reception, your phone will have mind-blowing internet speeds.

"Its current footprint focuses on CBD locations and selected regional centres where more than 4 million people live, work or pass through every day," said Telstra consumer executive Kevin Teoh.

"We have started rolling out 5G in 10 cities around Australia. Over the next 12 months or so we expect our 5G coverage to increase in area almost five-fold and reach into at least 35 Australian cities."

Samsung mobile vice president Garry McGregor said Australia is just the third country to receive its first 5G smartphone.

"There has been many years of research and development to get to this point – and today represents the next chapter for what mobile technology can offer to Australians."

How much does it cost?

Telstra customers who bought the Samsung Galaxy S10 Plus earlier this year are eligible to receive a free upgrade to the S10 5G, which actually has a larger screen, a better camera and a higher-capacity battery.

The new 5G technology, understandably, doesn't come cheap during these early stages. The Samsung Galaxy S10 5G 256GB on Telstra's XL consumer plan will cost $144 per month on a 24-month contract.

Telstra has also this week released a HTC 5G hub device, which allows a SIM card to provide wifi for 20 devices. Pricing for 5G for that device will be revealed next month.

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