Heating & Energy

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Water heating options

Water heating is about a third of household energy use. So if you want to reduce your power bill, hot-water use is a good place to start. If you do it right and target the hot water that just gets wasted, the only difference you should notice is your energy bill shrinking.

We also explain the types of systems available, their advantages and drawbacks.

The cost of a shower

A daily shower can cost a surprising amount of money. And that's for your average adult – much less teenagers.

We’ve calculated the costs of heating water with a standard electric water-cylinder, natural gas (storage and instant), LPG (storage and instant), a heat-pump water heater, and a woodburner wetback.

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Reduce your use

Top tips for cutting down the amount of hot water you use.

  • Rinse dirty dishes in cold water rather than hot before you put them in the dishwasher.
  • Don’t use hot water to wash your hands at a sink where the water gets hot just as you turn off the tap.
  • Installing an efficient showerhead if you have mains-pressure hot water could save you around $500 a year. Efficient showerheads have a maximum flow rate of 9 litres a minute but some can be as low as 6 or 7.
  • Fixing a dripping hot-water tap could save you over $35 a month. A drop a second might not seem like much but it adds up to more than 80 litres a day – all for the lack of a washer costing a couple of dollars.
  • Installing volume-control aerators on taps can halve the water flow through them. The air mixed into the water stream means you don't notice any difference in how well the tap "wets". (But don’t use them on taps you regularly use to fill sinks, buckets or baths. You'll end up waiting twice as long.)

Cut your losses

Check out your hot water cylinder. Older non-A-grade cylinders will leak heat.

  • A hot-water cylinder that’s warm to the touch will benefit from a cylinder wrap. This reduces the heat loss and saves you money. (Modern hot water cylinders have better insulation, so fitting a cylinder wrap won't have quite as much pay-off but will still be cost effective over the life of the cylinder.)
  • Get the temperature of your cylinder checked the next time your plumber is at the house. The water needs to be 60°C or a little over to kill any legionella bacteria, but any hotter than 63°C and you’re just paying for extra heat lost from the cylinder. You can’t tell the cylinder temperature at a tap because you should have a tempering valve that limits the hot water you use in the house to 55°C (to avoid scalding).
  • The first metre or so of the hot-water pipe coming out of the top of the cylinder can lose a lot of heat even if there’s no hot water flowing. Putting pipe lagging on at least the first metre can markedly improve heat retention.

Electric hot water cylinders

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Gas hot water cylinders

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Gas continuous-flow heaters

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Heat pump water heaters

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Solar heating

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Continuous electric

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Wetbacks

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