Power
Most rental campervans run a house battery topped up by the engine while driving and, on better-equipped vans, a small roof-mounted solar panel. It's enough for lighting, charging phones and laptops, and running a compressor fridge, but not for anything that draws serious current — a kettle or hairdryer will drain a house battery fast. If you're stopping for more than a day or two without driving, keep an eye on the battery monitor and plan a driving day or a powered campground stop before it runs flat. Powered sites (holiday parks, not freedom-camping spots) exist specifically for this — a night plugged into shore power every four or five days is a common rhythm for longer trips.
Water
A self-contained van's fresh water tank is sized to the standard's 12 litres per person per day, which sounds generous until you're doing dishes and a quick wash out of it too. Refill at any public tap, holiday park, or i-SITE visitor centre — most are happy to top up a van's tank for free or a small donation. Treat any water you collect from a stream or lake as untreated unless you know otherwise; New Zealand's backcountry water can carry giardia, and it's not worth the trip home spent unwell.
Grey water and the toilet
Grey water (sink and shower runoff) empties only at a proper dump station — never onto the ground, even on grass, even "just a little." Cassette toilets empty at the same dump stations, which are free and common at holiday parks, i-SITEs, and dedicated roadside stations sign-posted with a blue dump-station symbol; both CamperMate and Rankers map them alongside campsites. Emptying illegally is one of the most heavily enforced freedom-camping breaches precisely because it's what causes councils to close zones for everyone.
Cooking
Most vans carry a small gas hob (butane or propane, refillable at petrol stations and some holiday parks) rather than an oven — meal planning leans toward one-pot dishes, pre-chopped ingredients, and food that doesn't need much prep space. A chilly bin or 12V fridge handles perishables; supermarkets exist in every town of reasonable size, so daily or every-other-day shops are normal rather than stocking up for a week.
Laundry and showers
Holiday parks are the default for both — most have coin-operated washing machines and hot showers open to non-guests for a small fee, and they're common enough (even in small towns) that a laundry stop every week or so is easy to fold into a route. Some DOC sites and public facilities have cold showers; genuinely off-grid freedom-camping nights mean no shower until the next stop with one.
Staying connected
New Zealand's mobile coverage is solid along main highways and in towns but drops out in exactly the remote, scenic spots freedom camping is best in — Fiordland, much of the West Coast, and parts of Northland and the Catlins included. A prepaid NZ SIM (the three main carriers are Spark, One NZ, and 2degrees) covers most of the country; download offline maps and any campsite-finder app's data before heading somewhere remote, and treat no-signal nights as a normal, expected part of the trip rather than a problem to solve.