The navy is back to full fighting strength after a multi-million dollar upgrade to the Anzac frigate HMNZS Te Mana.
Te Mana, one of the navy's two frigates, finished sea trials last week after a seven-month refit when engineers put in new diesel engines, which significantly improved its performance and reduced fuel costs.
The ship also has a jet engine which is used for high speed running.
Earlier this year Te Mana's sister ship, HMNZS Te Kaha came out of a refit with the same engine upgrade.
The new engines cost about $57 million for both ships.
While the new engines are more economic, they will not allow the ships to go faster than their top speed of 27 knots.
The old engines could push each of the two frigates to 18 knots before a gas turbine kicked in for high-speed running.
The new engines could go to nearly 22 knots before gas turbines took over, making the ships more economic to operate.
Te Mana's engines had reached the end of their economic life span of 24,000 hours.
The ship also had auxiliary generators replaced, its quarterdeck deck space reduced to give added buoyancy and provide space for a new gymnasium and a relocated laundry, a new communications and control system and a modernised Phalanx gun system.
The 20mm gun system was the last line of defence against anti-ship missiles and aircraft but could also be used against fast inshore attack craft.
The cost of the upgrade to the gun systems on both ships was about $25m.
Both ships were alongside at the Devonport naval base in Auckland as the navy prepared to wind down for the Christmas and New Year break.
Te Kaha is expected to be in commission until at least 2025 and Te Mana until 2028.