Under Spain's favourable tax laws, temporary non-Spanish residents are taxed at 24%, with minimal social security contributions, as compared to the top rate of 43% for Spanish nationals.

The costs of going green can be "minimal to non-existent if a sustainability policy is carefully thought out and cleverly implemented," Kaestner says.

Winemaking techniques are a factor also as are the viticultural techniques of the vineyard, such as dry irrigation or minimal or non use of pesticides.