I recently switched to Grey Power Electricity because the quote they gave me was $9 per month less than my previous electricity provider. A saving of $108 p.a. (single household user assessed on 100 units). To qualify for Grey Power Electricity you have to first become a member of Grey Power (contactable via your local telephone directory). Membership costs about $20 p.a. With that you get a discount book and other benefits. If anyone is interested in getting their own quote from Grey Power Electricity they can contact them on 0800 473 976 Mon-Fri and have an electricity bill handy for comparison and quote.
[Also try powerswitch.org.nz. It makes shopping around for the best power price deal easy.]