What is the electricity voltage in New Zealand?
Depending on where you are travelling from, it is likely that you will need a transformer. New Zealand operates on 230 volts (50hz), so appliances on other voltages will need a transformer.
Finding the voltage your devices operate on
Most devices state their operating voltage near where the power cord plug. If the voltage isn't clear then you may need to check on the manufacturer's website for more information.
Adaptors for New Zealand power sockets
You will also need an adaptor to suit NZ sockets. These can be purchased at the airport or online if you can't find one in your local stores. New Zealand sockets are usually three pins, rather than the two pin sockets that you may find in Europe and North America. (See Socket 1 on the useful socket comparison table available here.)