Water & energy efficiency

What matters most to you?
The perfect dishwasher balances washing performance against water efficiency, and drying performance against energy efficiency. But the perfect dishwasher is hard to find: dishwashers with high scores for washing are often less water-efficient; and those that are best at drying use more energy to do so.

A dishwasher’s main job is to wash dishes properly. It’s false economy to choose a model that has excellent water and energy efficiency but can’t do its main job: you’ll just end up using more water and energy rinsing and re-washing dishes.

To bring the focus of our test back to basics – cleaning your dishes – we've revised our rating scale so that washing is the most important part of the scoring.

Washing performance now accounts for 55 percent of the overall score (up from 40 percent). Drying performance, water and energy efficiency are each 15 percent. This means the overall scores for our previously tested dishwashers have changed.

Individual scores for washing, drying water efficiency and energy efficiency vary amongst our recommended models – so when choosing a new dishwasher think about what matters most to you.

Tip: You can achieve almost-perfect drying if you’re in the kitchen when your dishwasher finishes its drying cycle: just open the door to let most of the steam out.

Energy labels
The more stars, the better the efficiency. But make sure you're looking at the latest standard – AS/NZS 2007.1:2003. Ratings for this standard are based on a normal cycle, which takes longer and uses more hot water than an economy cycle. Under the old standard, the ratings could be based on an economy cycle.

Some models create an economy cycle by dispensing with the drying heater. It saves on power, but means you could have to get out the tea towel. This rather defeats the purpose of a dishwasher!

Water connection
While a hot connection usually gives shorter wash times, electricity costs can increase due to heat losses from the water pipes, especially if the dishwasher is well away from your hot-water cylinder.

Check the maximum allowable hot-water temperature for the machine. Your hot water supply may exceed this if you have a wetback system.

A cold-only connection is cheaper to set up and run, and more energy efficient, as the dishwasher itself heats and uses exactly the amount of hot water needed. A cold pre-rinse (which many models use) is also effective at loosening egg and cereals.

Is a dishwasher cheaper than handwashing?
It could be. If you wash by hand, we estimate you'll use around 40 litres of hot water (at least two sinks full) to wash the same pile of dishes that fit into a dishwasher. That costs about 13 cents. If you rinse the dishes with hot water (before or after) the cost rises.

Use the normal cycle of an efficient dishwasher, and it will cost you about 16 cents. Use an economy cycle, which leaves you with some drying, and the cost reduces to about 13 cents. The load will have had a pre-wash rinse, a detergent wash and a rinse.

Which detergent?
We're often asked what the best detergent is. The answer may well be that it doesn't matter - the dishwasher matters most. In a huge trial of detergents that included most of the familiar Kiwi brands, the Australian consumer organisation Choice used 200 households to do home testing.

Despite big differences in price, the testers didn't find equally big differences in performance. As one said: "All the products were good and we'd be happy to use any of them."