It had taken the bank more than a year to secure its Queen St site, near the intersection with Shortland St, he said.
The Co-Operative Bank was also investing heavily into its online offering, including a new service that allows prospective customers to join the bank through its mobile app.
He said the bank planned to be a "fast follower" in mobile wallet technology, which allows consumers to make payments with their smartphones.
BNZ and ASB plan to use technology developed by Semble - a joint venture owned by Paymark, which is owned by the big four Aussie-owned banks - to offer mobile wallet services to customers.
Westpac is developing its own mobile wallet system, while ANZ has said it is "assessing developments" with the technology.
McLachlan said The Co-Operative Bank could offer Semble's technology to its customers once it was proven effective by other lenders.
"We're quite happy to let others muck around in that space and then we'll follow quickly."
The Co-Operative Bank added 10,000 new customers in the year to March, taking the total to 125,000.
It paid $1.3 million in rebates to customers in the last financial year, up from $1 million a year earlier.
The size of rebates depends on how much business customers do with the bank.
McLachlan said they ranged from $7 up to $400 - with an average of about $20 - in the year to March 31.
He said the bank's rebates were expected to "grow materially" over time.