Core banking systems are the main way credits and debits are recorded, and the system that maintains transactions, histories and balances.
"It's the engine room that links individual account holders to the banking system."
Mr Earle said while the previous system needed "an army of engineers" and several days to change things, the new system enabled new products to be delivered within hours.
It also meant it was easier to "plug and play" when connecting to new mobile banking apps.
The launch is the culmination of two years' hard work by the team from every branch to head office.
"It's exciting for NZCU Baywide and our customers because we have updated the foundation for all our operations to give us wider scope to improve services in the future for many more people."
While the credit union did not have the financial backing of the big banks, the new system would enable it to be flexible and innovative.
"For us we can innovate on a smaller budget and keep pace with them."
Originally established in 1971 as Whakatu Freezing Works Employees' Credit Union, NZCU Baywide has grown to 16 branches throughout the central and lower North island.
"This is the largest change project we've carried out in our 47-year history," chairman Iain Taylor said.
"It responds to the needs of customers who are familiar with the types of systems used by leading mainstream banks - while we needed to be on a par with them, we also have ambitions for even better services in the future.
"This is a big result for us, but it's only the start. We are already working on phase two, which is modernising our internet and mobile banking platforms."