The purchase of the vehicles was supported by an additional $6m investment from the Government.
Hiringa chief executive Andrew Clennett said he was delighted to reach this milestone in the roll-out of the refuelling network, which would help decarbonise the country's heavy vehicle fleet.
"This achievement is the result of collaborating with our key partner companies and working closely with central and regional government, all of whom have the central aim of making green hydrogen refuelling for heavy transport a reality in New Zealand.
"The New Zealand Government's support in the early decarbonisation of heavy road transport has played a vital role in providing many logistics operators and their customers with the confidence to invest in and support zero-emissions fuel cell electric vehicles."
The hydrogen fuelling stations would be owned and operated by the Waitomo Group, which would incorporate them into existing fuelling sites.
Clennett expected the four fuelling stations and the vehicles would be operating commercially by the end of 2022.
Hiringa Energy would supply the hydrogen for the network, which would be produced at the refuelling sites through a process of electrolysis in the initial stages.
The company is planning to build its own hydrogen production plant which harnesses wind power. The hydrogen would then be distributed to the fuelling stations.
It would take 10 to 15 minutes to refuel one of the trucks, roughly the same time it took to fuel a diesel-powered truck, Clennett said.
He said the fuel would still be more expensive than diesel, but hoped to see price parity in the middle of the decade as the price of diesel increased and cost of hydrogen fell.
Clennett said tests using data had been carried out to ensure the trucks, which weigh 50 tonnes, could meet local regulations and meet the country's demanding road conditions.
"Capable of over 600km of range between refuelling stops, this is similar to existing diesel-based offerings," he said.
The price of the trucks would come at a premium, but Clennett hoped that through the Government's subsidy it would not result in dramatically higher leasing or freight costs.
He anticipated the price point would come down at a rate of 10 to 15 per cent per year as demand for the vehicles increased, allowing the manufacturer to produce the trucks at scale.
Hiringa Energy was planning to expand its network to the South Island through 2023, and would have more than 24 stations across the country in the next four to five years, Clennett said.