Dishwasher energy and water efficiency


More energy efficient = low performance?

How efficient is your dishwasher?


Did you know that according to the Australian Bureau of Statistics, each household uses about 31 litres of water a day in the kitchen sink? Here at CHOICE, we haven't seen a dishwasher that uses that much water for a long, long time – not since the bad old days. Which means in this day and age, using a dishwasher means you really do save on water.

Newer models are now even designed so you don't need to rinse your plates before you wash, saving on the pre-rinse water too! And all that mucky work. But how well do these "efficient" dishwashers really work?

More energy efficient = low performance?

Parts of Australia experience water and power shortages, so eco-friendly upgrades are becoming more important when you're looking to buy or replace a dishwasher. The big question is, does a more efficient machine come at the expense of performance? We think so.

There are exceptions, but our tests show that machines that dry the dishes well tend to be less energy-efficient, indicating that good drying performance mostly comes at the cost of higher energy use. Few dishwashers manage to score very well for energy efficiency when tested on the "normal" cycle, which most people use.

Most dishwashers, however, do wash well so one way you can save water is by not rinsing plates before packing them – just scrape the food scraps off.

Our tips for choosing your next dishwasher:

  • Choose a machine with a very high energy efficiency score and low water usage. The downside to this is that you may sacrifice how well the dishwasher dries (see below).
  • Using the fast/eco wash cycle, and waiting until before you go to bed to run a cycle or choosing a delay start option so you use energy at cheaper rates.
  • Avoid a smelly dishwasher or having to pre-rinse dishes by choosing a model with a good auto-sensing program or half-load option, so you can wash a smaller number of dishes more often and economically.

For more advice and tips on choosing a dishwasher, see our dishwasher buying guide.

Can I save energy using hot or cold water connection?

In some cases yes, but you'll have to check the manual to see whether the dishwasher accepts a hot water connection. There are some pros and cons to both connections.

Cold water connection

Pros

  • You have full use of programs at different temperatures, such as economy, glasses, bio (programs suitable for enzyme-based detergents), and so on.
  • You'll get better results when using enzyme-based dishwasher detergents.
  • If you have a limited hot water supply, it doesn't get used up by your dishwasher – it'll heat up its own water.

Cons

  • Longer cycle times than with hot water (because of the extra time required to heat up).

Hot water connection

Pros

  • You can take advantage of cheap off-peak or solar hot water.
  • Faster cycle times because the dishwasher doesn't need to heat its own water.

Cons

  • You lose program versatility – for example, you can't effectively use eco, economy or glass/fast wash programs, which wash at lower temperatures.
  • You may need a tempering valve to reduce your hot water temperature if the manufacturer of your dishwasher recommends a lower inlet temperature. Higher than recommended inlet water temperatures can shorten the lifespan of the inlet valves.


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