Employment Relations Act 2000, s 67D(6)
Relevant factors for what will be reasonable compensation for making yourself available above your guaranteed hours include:
how many hours you have to make yourself available for
how that number compares to the number of guaranteed hours
any restrictions placed on you – for example, if you can’t drink while you’re on call, or if you have to stay local rather than just being available by phone
your regular pay or salary.