Past 7 nights, most fleets switch to a weekly rate that's roughly 15-25% cheaper per night than the daily rate. That makes 14 days the sweet spot for cost-per-day. A realistic shoulder-season budget for a couple in a 2-berth is NZ$300-560 per day all-in, scaling to NZ$465-750 for a family of four in a 4-berth. Driving distance for a typical 14-day route is 2,200-2,600 km depending on whether you cross the Cook Strait.
Couple in a 2-berth, 14 nights, shoulder season
Vehicle: NZ$2,100-3,500. Fuel (2,400 km, diesel): NZ$540-720. Holiday parks (12 powered nights at NZ$55-75): NZ$660-900. Food and groceries: NZ$560-840. Activities (Milford + one extra): NZ$280-440. Insurance buyout: NZ$420. Ferry (if both-island route, 6m vehicle plus 2 passengers): NZ$320-450. Total: NZ$4,880-7,270.
Family of four in a 4-berth, 14 nights, shoulder season
Vehicle: NZ$3,200-5,200. Fuel (2,400 km, larger vehicle ~14L/100km): NZ$640-870. Holiday parks (12 family powered sites at NZ$70-95): NZ$840-1,140. Food and groceries: NZ$840-1,260. Activities (2-3 paid stops): NZ$420-680. Insurance buyout: NZ$420. Ferry: NZ$380-520. Total: NZ$6,740-10,090.
Peak summer adjustment
Mid-December through January adds roughly 25-35% to the vehicle and 10-15% to holiday parks and ferries. A couple's NZ$4,880 shoulder trip becomes NZ$6,200-6,800 in peak. A family's NZ$6,740 becomes NZ$8,800-9,600. Book the ferry at the same time as the vehicle in peak season — January Wellington-Picton sailings sell out 3-4 months ahead.
Note on prices. NZD ranges above are mid-2026 estimates from current rental fleet quotes and published holiday-park rates. Peak summer (mid-December through January) sits at the top of each range or above; shoulder season (March-May, October-November) sits at the bottom. We'll confirm live numbers for your dates when you send us a trip outline.