Some advantages to the grower from the IWP scheme are already being reported. In addition, Montana reports that buyers are impressed by the environmental reports produced. The nuts and bolts of the scheme are straightforward. For a grower to comply, they must have no unacceptable scores. External auditors audit each grower every three years.
Membership is voluntary, but some wine companies require their contract growers to be members.
The scheme is also financially supported by the New Zealand Grape Growers' Council. At first glance, it looks like the answer to an environmental regulator's prayer. Vineyard practices that impact on the environment are steadily improving. More than that, growers are making the improvements voluntarily, without the need for regulation, monitoring, enforcement or education campaigns by local government, with their attendant costs. The practices of growers who do not join the scheme are also improving, as they see the cost savings and other benefits from the IWP practices.