Campsites are of a very high standard in New Zealand with powered sites, hot showers, full kitchens, TV and entertainment rooms. When you hire a Spaceship a large variety of information is included on all the campground options in New Zealand. This includes the 250+ DOC campgrounds (some of which are free camping).
The average nightly rate will be between NZD$8-$20PP/Night. Some camping grounds will allow you to use their facilities for only a few dollars without actually paying to stay the night and there are also good public facilities to use free of charge in many locations throughout the country.