Manabus.com

They are also in conjunction with the Naked bus so you get alot of choices with ride times and ticket prices.

It was fun traveling down to Auckland on a double-decker bus. The drivers are really friendly and the fares are really good, compared to other bus companies doing long-haul trips. I haven't tried it (yet) but they also have a sleeper bus, so you can sleep in comfort, and arrive fresh at your destination. Nice clean, modern buses with a good fare structure. Unfortunately, you can only pay online, so you need to book in advance. Otherwise, Highly recommended.

The cheapest but around, they have the mana bus and the naked bus which seem to intertwine. I love their overnight bus as they have actual beds you can pay to sleep in on the bus which have charging points and everything which is awesome. They are well worth it and you can get quite a good sleep if you bring a pillow!

Such a great bus! i usually travel on intercity but i decided to try Mana bus as they had such cheap prices. The journey was the same length and the bus just as comfortable but i saved $20 on the ride so it was very much worth it.

Very cheap and good bus company. They run from Auckland to Wellington and the tickets can be as little as $18 which is great. There is wifi on the bus and the seats are very comfortable.