Water heating options
Most New Zealand homes use electric hot water cylinders. Others use gas or LPG hot water cylinders or instant gas hot water systems (which heat water as you need it). Both gas and electricity produce greenhouse gas emissions – but gas produces less than electricity when the latter is generated by burning fossil fuels.
Instant electric water heaters are sometimes used for washbasins or showers and are energy efficient because they heat water where is is used, eliminating heat loss from storage cylinders and hot water pipes. Drawbacks with instant electric hot water systems are that they are typically used when electricity is charged at the peak rate and they also require separate wiring for large flow-rates.
Instant gas hot water systems provide continuous hot water that never goes cold, as the water is heated as it flows to the tap. Gas is only used when your hot water tap is turned on.
There is no storage cylinder, which means there are no energy losses from keeping water in a tank hot. Systems can be up to 95 efficient and water temperature is set at a control panel reducing the risk of burns.
If you’re looking at an instant gas hot water system, look for one with automatic ignition not one with a pilot light. Pilot lights use gas even when the water is not being heated.
This is the most energy-efficient water heating option – the sun’s energy is free, unlimited and non-polluting. For many households, it is also the most economical – converting to solar can pay for itself over time through lower energy bills.
Converting to solar is particularly worthwhile for larger households, households that use a lot of water and for homes in sunnier areas.
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 the pros and cons of other water heating systems too.
Heat pumps use electricity far more efficiently than ordinary electric water heaters. They are usually used for space heating but some are designed to heat water.
They work by extracting heat from the air outside, using a process that’s like a refrigerator working in reverse.
Manufacturers often claim heat pumps give three times the heat.
Heat pumps lose efficiency as the temperature outside gets lower, so they are less efficient in winter.
Ask suppliers for the heat output figures
A wetback is a useful way to heat water in winter if you have a woodburner and a reliable source of dry, untreated wood.
You can also use a wetback with an open fire but open fires are very inefficient.