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 swap a bottle at many service stations, The Warehouse, Mitre 10 and other outlets. 

If you have Pre Purchased Gas or the Express Return Pack then you need not return your campervan with a full gas bottle.