Gas bottle sizes and gas operated equipment differs with different campervans. Campervans with gas operated cooking, heating and water systems will use gas quicker than campervans with only gas cooking. 

If you run out of gas, you can refill the LPG bottle at many outdoor camping stores. Alternatively, if in NZ you can use the Swap 'n' Go service at many service stations. You can search for the closest LPG Bottle Filling or Swapping station in the thl Roadtrip App.

 If you have Pre Purchased Gas or the Re-Fuelling Pack then you don't need to return your campervan with a full gas bottle.