The light, the fridge and the cigarette lighter (where you can recharge the batteries of your cell phone and digital camera, if you have a charger with adapter) run on a 12 volts battery, which reloads while driving. The sockets (and in some models the heater) need 230/240 volts (50 hertz). You can only make use of them when you have a powered site at a campground (where you can plug the vehicle into 240 volts mains power). If you are not from New Zealand, you will need a converter to operate your electronic equipment.
Depending on your electricity needs and the capacity of the waste water tanks you will need to stay at a campground approximately every 3rd night.
On the outside of the vehicle is a flap with 1 or 2 gas bottles behind. For taking hot water and for operating the gas stove the gas tap must be open. In some vehicles, the fridge runs partly or completely on gas as well. It's very important to close the gas tap when going on the ferry. Empty gas bottles can be refilled at garages and petrol stations.
At a dump station you can empty the waste water tanks (grey + black water) and fill up the fresh water tank. You'll find dump stations at most of the campgrounds and at some petrol stations. There are new ones and odd ones – if you aren't sure if it is actually a dump station, ask someone and don't empty your waste water into a common drain. It's needless to say that this is unwanted. To empty the waste water tank, fix the waste water hose (vehicle equipment) at the waste water pipe under the vehicle and hang the other end of the hose into the drain at the dump station. Wear gloves!
When you open the lever on the pipe, the waste water runs off. Use the water tap which is at the dumpstation to clean the waste water hose and the black water tank (if extra). There should be another so-marked tap to fill up the fresh water. Often there's a fresh water hose at the dump station – but you should have received one with your vehicle equipment, too. There's a list of all dump stations and further information on the website of the Ministry for the Environment.