Electric hot water cylinders

Electric hot water cylinders are the most common form of water heating in New Zealand.


  • Relatively low upfront cost.
  • Some have smart controllers which vary when and/or to what temperature the hot water is being re-heated according to your household’s needs. By not keeping the cylinder constantly full of hot water when it’s not needed, these controllers are primarily designed to reduce a cylinder’s heat loss through its insulated walls. With a conventional modern electric cylinder, this heat loss costs about $90 to $150 per year. A smart controller can cut a portion off of this – by how much depends primarily on how much “spare capacity” your cylinder has, and the effectiveness of the smart controller.
  • You can buy cylinders with additional connections suitable for having a solar water heater, heat pump water heater or wetback added in the future.
  • Can be put on a controlled or night-rate electricity supply to get a lower electricity price.
  • A night rate electricity tariff in particular could lower your hot water bill substantially. It's not available in all areas of the country though - check with your electricity supplier first. Before switching to night rate, test that your cylinder is big enough to store a day's water. Switch it off first thing in the morning and back on before you go to bed for a couple of days to see if you run out of hot water. If you have enough hot water to see you through, organise a night rate tariff with your electricity supplier. For those with insufficient hot water, some electricity providers offer a night rate tariff with an additional hot water boost during the day. Check with your provider to see if they offer this service.

Keep in mind

  • The running costs of electric hot water cylinders are relatively expensive compared to other water heating options (unless a cheaper night rate tariff is used).
  • To reduce heat loss, put a hot water cylinder wrap around the cylinder, and pipe insulation around the first metre of the hot water pipe, particularly if you have an older hot water cylinder installed pre-2002. They are available from hardware stores.
  • The system needs to be correctly set up to ensure the water in the tank is regularly heated to 60oC to prevent the growth of legionella bacteria.
  • Use our water heating systems tool to compare the upfront and ongoing costs of different water heating options for your situation.

?Water heating systems tool

How they work

Electric hot water cylinders use an electric element in an insulated tank to heat the water to a temperature set by a thermostat.