Water heating solutions

iPlumber can help you choose the best option for hot water in your home or business

Hot water for less

The most efficient water heating options (in order) are:

Solar Water Heating

Hot Water Heat Pumps

Fireplace Wetbacks

Continuous Flow Hot Water

Gas Hot Water Cylinders

Electric Water Heaters

Solar water heating

Solar water heating provides large energy savings using the sun, however to maintain a hot water supply when the sun doesn’t shine, solar hot water systems usually have backup heating – so you will still need to consider other water heating systems as well.


  • Solar hot water heaters use the sun’s free, unlimited energy.
  • Well-installed systems can deliver up to 75 percent of hot water heating over a year, in most parts of the NZ.
  • Solar water heating is particularly worthwhile:
    1. when used in conjunction with a wetback on a fire that’s used as a primary space heating source over the colder months
    2. when used as a very simple pre-heater with no controllers, or pumps, and plumbed into the pipe feeding into your water-heating cylinder.


  • High initial cost compared with other water-heating options
  • Systems can be complex to design and install correctly
  • Usually need some backup system for when the sun doesn’t shine
  • Solar Hot Water Systems also need some annual maintenance.

Heat pump water heating

Hot water heat pumps use electricity far more efficiently than ordinary electric water heaters. Heat pumps work by extracting heat from the air outside, using a process that’s like a refrigerator working in reverse. Heat pumps are usually used for space heating, but the same technology can heat water. While heat pump hot water systems are more expensive to purchase than a standard electric hot water cylinder, their efficient operating costs mean that they are a good long-term investment

There are two main types of hot water heat pump systems:

  1. an all-in-one system where the heat pump is part of the hot water cylinder; and
  2. However we recommend a split system where the heat pump is located outside and the hot water cylinder (which can be a modern electric cylinder) is located either inside or outside the house.


  • Consumer NZ research shows that a well specified and installed heat-pump water heater would reduce your hot water bill by two-thirds over standard electric water heating
  • Heat pumps are up to 2-3 times better than standard electric hot water cylinders with warmer outside temperatures


  • Hot water heat pumps can be noisy (no noisier than a standard heat pump)
  • Hot water heat pumps are less efficient in winter

Fireplace Wetbacks

A wetback is a useful way to heat water in winter if you are replacing or installing a wood or pellet burner near your hot water cylinder. Ideally, the hot water cylinder should be located as close as possible to the fireplace to minimise the heat loss through pipes.


  • Wetbacks are most useful in areas with a cold climate and a long heating season, and where the wood or pellet burner heats the house well
  • Wetbacks can complement solar hot water, particularly to ensure year-round hot water in areas with low winter sunshine
  • Wetbacks are useful in areas with intermittent energy supply and abundant wood


  • Larger diameter water pipes (25mm) are recommended.
  • Many councils have regional clean air plans which strictly regulate the use of wood and pellet burners
  • There is no restriction on wood burners or clean air policy in Hamilton, but you will need council consent for a fireplace installation.

Natural Gas/LPG Califonts

Califonts offer instant and continuous flow of hot water – this style of gas water heaters are also known as a tankless, instantaneous gas hot water system.


  • Califonts are very efficient for up to 2 occupants, especially with natural gas – you only pay for what you use
  • Califonts have a range of units which include very high efficiency condensing models.
  • Califonts are one of the cheaper types of hot water heating to install.
  • Califonts can be a great way to pre heat water going into a larger storage cylinder which has a high demand.
  • Califonts have optional temperature controllers
  • Califonts are excellent for use where space is a premium

For instant gas hot water systems, ask for one with automatic ignition as those with pilot lights use gas even when the water is not being heated.


  • Califont continuous flow heaters have a short delay while heating water
  • If there is a power cut you will have no hot water.
  • These can be easily removed and targeted for theft, so addition of a security bracket can be beneficial here.
  • LPG Califonts can be one of the most expensive forms of hot water heating, best suited for 1-2 occupants or holiday homes.

Natural Gas/LPG Hot Water Cylinders

  • Gas hot water storage systems have a quicker heat recovery time than a comparable electric hot water cylinder.
  • You do need to check with council if consent is required when moving a storage hot water cylinder to a different location, inside or outside the dwelling.


  • With gas hot water cylinders you have hot water stored so there are no delays in heating water
  • Gas hot water cylinders have a very fast recovery time, reheating up to 200 litres per hour.
  • Gas hot water cylinders are cheaper to run than a califont continuous flow system for 4 or more occupants
  • Gas hot water cylinders are cheaper to run than electric hot water cylinders
  • Cylinders are a source of stored water for emergencies


  • Internal gas cylinders need ventilation and flues installed
  • these are more prone to rupturing and require preventative maintenance annually, a safe tray is a great idea if being installed indoors.

Electric water heating

Instant electric hot water systems & hot water cylinders

Instant electric water heaters

Instant electric water heaters are more energy efficient because they heat water only when it is used, eliminating standing heat losses from hot water sitting in storage cylinders and hot water pipes. However, they do have two drawbacks, in that they:

  • are typically used when electricity is charged at the peak rate
  • require separate heavy duty wiring for large flow-rates.

Instant electric hot water systems are best used as a supplementary system where an outlet is a long way from the main hot water system (for example, for washbasins or showers).

Electric hot water cylinders

Older hot water cylinders are often poorly insulated, leading to heat loss. Electric hot water systems that are less than “A” grade insulated are worth wrapping with more insulation. If you do insulate them, they must be entirely insulated, otherwise the thermal benefit will be minimal.

Most New Zealand homes have an electric hot water cylinder. Older cylinders tend to be very small with low pressure and are often poorly insulated, whereas modern electric hot water cylinders are high pressure/mains pressure cylinders. You do need to check with council if consent is required when moving a storage hot water cylinder to a different location, inside or outside the dwelling.


  • Electric hot water cylinders are relatively cheap to install
  • You have hot water stored for a few hours in case of a power cut
  • Cylinders are a source of stored water for emergencies
  • Electronic timers and Smart Cylinder options can reduce running costs


  • Less efficient to run that most other water heating options
  • Mains and low pressure hot water cylinders do require annual or bi annual maintenance, and if neglected they can burst causing damage to floors and walls (fitting of a safe tray is great way of preventing this but can cost around $300-500 extra).

Comparing Costs

EECA Energywise has an online tool to help you compare upfront costs (purchase and installation), annual running costs and lifetime costs of different types of hot water systems: http://bit.ly/EECA_WaterHeatingSystemTool

To see how much you’re currently paying, have a look at your bills over the last 12 months. It’s possible your hot water energy use is detailed separately on your bill. For an electric hot water cylinder, your hot water energy use may be referred to as ‘controlled electricity’ or come under a ‘Night Boost’.


If you have gas water heating, your gas bills may not list hot water energy use separately. If you use gas for cooking and space heating, have a look at some summer gas bills when you wouldn’t be using gas to heat your home.

If in doubt, contact your energy supplier for help with calculating the cost.

Need to replace an old hot water cylinder?

Or want help choosing the best option for hot water in your home or business?

Contact iPlumber

or have a look on Gen Less Water Heating System Tool web page.

iPlumber are the proud recipients of New Zealand Master Plumber of the Year Award for 2020
and we were also Waikato Master Plumber of the Year for 2019

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