The Electricity Commission says households are paying nearly $130 million a year more than they need to in electricity charges because of inefficient light bulbs.
It says despite a rapid uptake of energy efficient bulbs, nearly 90% of homes still have mostly older-style light bulbs.
Commission chairman David Caygill says one home in every six has no energy-saving light bulbs fitted.
Mr Caygill says ordinary bulbs can cost just $1 but only last for about 1000 hours, as opposed to a $5 energy-saving bulb, which lasts between 6000 and 15,000 hours.
The commission is trying to make households aware that there are efficient bulbs for almost any room.