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In Hot Water

Water heating makes up to 35% of the energy bill of the typical kiwi household and with the cost of energy continuing to rise, the selection of the correct water heater is now more important than ever.

To make significant efficiency gains over time choose how you heat your water wisely as whichever system you choose, using it efficiently will mean less energy and water is wasted.

Heat pump water heating (HPWH)

Water heating using heat-pump technology is a good option when it comes to using renewable resources. Depending on where you are situated in New Zealand, energy efficiency from HPWH will be similar to and can often exceed solar. HPWH uses energy stored in ambient air as its main energy source. With all installations, give some thought to how close it will be to bedrooms and neighbours, given that there is some level of noise generated regardless of the model chosen.


With roughly two thirds of New Zealand’s power supply sourced from renewable sources, electric storage water heaters are a smart, low capital cost alternative to solar and heat pump options while still being relatively environmentally friendly. Insulation standards (MEPS) are such that heat losses from modern cylinders are minimal. Cylinders manufactured before 2004 did not have such high levels of insulation should be wrapped to prevent heat loss. An insulating hot water cylinder wrap costs around $70 and can reduce hot water costs by up to 20%. Electric water heating is still the most popular choice for New Zealand homes.


Water heating using gas will normally give faster recovery than electric making it a good lifestyle choice where the likelihood of exhausting your hot water supply frequently may be an issue.

There are two types of gas water heater – storage and continuous flow (sometimes referred to as instantaneous). Gas storage works on similar principles to electric storage, only the element is replaced by a gas burner. Continuous flow systems heat the water on demand. In low usage situations they are more efficient than gas storage as they use only a small amount of electricity on standby and do not need to store any hot water. However, in higher usage or frequent start and stop situations, their efficiency tends to be lower than a storage system due to the frequent heat loss during the cool down cycles that occur between start-ups.

Further on down the line

Regardless of what type of hot water system you install, there will always be heat losses as water travels from the heating source to the point of use, for example your kitchen tap or your shower. If you are building or renovating, you can minimize these losses by specifying a thermally efficient pipe such as environmentally friendly Fusiotherm, or by wrapping your pipes in insulation (called “lagging” in plumbing terms) as you go.

Flow restrictors or aerating taps and showerheads can further improve your the efficiency of your hot water system. These use air or cold water pressure to reduce the amount of hot water that comes out of your tap or showerhead, magically without appearing to change the temperature or the pressure of the water on your skin. Neither are expensive to purchase and could end up saving you a lot of money off your power bill.

The cheapest way to be more efficient is to change your habits. Wash your hands in cold rather than hot water. If you like baths, try saving them for special treats. Try to reduce the length of your showers – every extra minute of showering adds up to around an extra $80 per year in water heating.

Every little bit counts, both towards your bottom line and the planet’s.

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