Power utility Eskom on Wednesday called on consumers to switch off geysers, pool pumps and all non-e.
Their owners were killed in battle in the 18th and 19th centuries and sent to Europe where collectors had an intense fascination with strange civilisations.
The largest repatriation of Maori remains came from nine museums and a university in France which handed them over to a group of tribal representatives in Paris earlier this week.
Elders were in tears as they welcomed them home in a traditional ceremony at the Museum of New Zealand, Te Papa, in Wellington, where experts will try to research their heritage in order to restore them to their tribal ancestors for burial.
About 500 more tattooed heads are believed to be held in other museums in Europe and the United States, which are reluctant to repatriate them for fear of setting precedents for the return of artefacts.