score:2
I made a page that does exactly that. It can also take costs for accommodation, car rental and daily food and entertainment budget into account. For the trip you mentioned it might cost you a bit more than NZD 300.
Keep in mind that it will cost you an additional ~NZD 200 your you want to take your own car with you from north to south island on the interislander ferry. If you rent a car, it would be better to drop it of on one side and hire another car on the other island, pretty sure the rental companies have some sort of arrangement for that.
Fuel prices right now are $1.80 (Auckland CBD) or $1.70 (Auckland south) for 91 unleaded, but the pricewatch site gives you a better indication of fuel prices across all of New Zealand. Your fuel consumption depends on a number of factors such as type of car, extra load, speed, terrain (flat vs. hills and mountains) your personal driving style, city vs. highway so it's really hard to come up with an exact number. If you have 2 people in a mid-sized car with lots of luggage I would estimate 9 l/100km, and everything below that is a bonus. The fuel consumption car makers advertise are usually done under ideal conditions, and the real consumption might be up to 20% higher during everyday trips.
Upvote:1
I think the bare minimum km you can connect those dots is 1881km. (See this link for distance derivation)
You'll go over about 3 passes, so that might increase your cost a little. You won't be going much over 100kph due to the high degree of speed enforcement so that may save you some gas money. You'll also find that on the west coast of the south island due to its remoteness that prices can be up to 50% more than in say Christchurch. So in a small car say 9L/100km @$1.40nz$/L that's about ** £116** . I would allow probably 25% more for side trips and running around.
Upvote:2
Fuel prices are low at present in NZ, but fuel prices will vary from region to region. Tank up in big cities, not small remote country towns if you can help it.
You can check average prices here: http://www.pricewatch.co.nz/Default.aspx?lyr=15&price_type=avg
I would work on an average price closer to NZ$1.75 per litre.
I assume you are driving a smallish model rental car, so will get good fuel economy and with open road running in the South Island you are probably looking at about 1500km, 9l per 100km = 135 litres or NZ$250.
I personally would not worry about fuel prices so much. You need to stay alert when driving long distances and I believe you will end up spending more on food and drink for yourselves. A couple of people could spend more than your petrol budget on one meal at a high end restaurant.
Upvote:6
There are a number of websites where you can check the evolution of fuel prices. Taking a random result from Google yields this one.
With a rough daily price you can then use an online tool such as numbeo to compute and estimate of tour fuel consumption, using miles-per-gallon-type (mpg) metrics, and thus an average price for your roadtrip.
The fuel consumption (mpg-like) measures are highly dependent on engine type, displacement, fuel type, and driving style (urban, highway, mixed). To get a correct estimate you might want to look first at what type of car you are thinking of renting. Then with that information you can find the mpg (or litre-per-100km) on the car maker's website, and you can then make an educated guess of the fuel consumption. To be safe you can always round up towards a higher fuel consumption rating.