Dishwashers versus Hand-washing

G Magazine

When it comes to washing up, is machine or man power best?

Dirty dishes in sink

It's time to wash up! But should you be using machine power or man power for the chore?

Credit: iStockphoto

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You've had friends over for a feast and then you suffer for it, altruistically shunning the dishwasher to wash the leaning tower of dishes by hand.

It's better for the environment than using a water-intensive dishwasher, right? Or are those newfangled machines efficient enough to pass the green test?

Out with the old

As with advancements in other white goods, better dishwasher design has resulted in substantial improvements in efficiency - so much so that replacing an old dishwasher can more than pay for itself because of reduced energy and water usage.

An Australian report for the federal government committee on Equipment Energy Efficiency (E3), found that from 1993 to 2005, water usage in the newer dishwashers was slashed by 39 per cent and energy usage was reduced by 36 per cent.

There is no need to worry about wasted energy in the manufacture and transport of a new dishwasher either.

According to a study published in Appliance Magazine, this comprises only five per cent of its total environmental burden; the energy associated with its daily use accounts for the rest.

The study assumed someone using the dishwasher for 15 years with 300 washes a year.

A life-cycle expert, Hartmut Kaebernick, who was most recently at UNSW, has concluded that dishwashing machine should "definitely" be replaced every seven or eight years.

If the cast-offs are disposed of through proper channels, recycling of parts and materials is likely.

Stars are significant

Spending a bit more on a machine with more stars makes a big difference.

The government's energy rating checklist shows that each additional energy star equates to 30 per cent less energy consumption.

As well, each extra water star means the machine will use 15 per cent less water.

Improved water efficiency also means less detergent can be used, which is better for our waterways. And if you choose a dishwasher detergent that contains no phosphates or which is certified by Good Environment Choice Australia, you'll get extra greenie points.

Testing hand-washers

But how do dishwashing machines stack up compared to washing by hand?

Bonn University's household and appliance technology professor, Rainer Stamminger, analysed the best dishwashers manufactured between 2002 and 2004.

He rated the efficiency of two machines washing 12 place settings (140 pieces). To account for a variety of dish-washing styles, Stamminger managed to convince 113 hand-washers to chain themselves to a sink.

Europe's best machines only used around 15 L and consumed between one kilowatt-hour (for a standard cycle) and two kilowatt-hours (intensive cycle) of energy to wash and dry the dishes.

The hand-washers, meanwhile, averaged a whopping 103 L, with one enthusiastic scrubber using 447 L!

However it should be noted that among the various hand-washing styles, the more common 'dishwashing economisers' used as little as 30 L of water.

Energy used by hand-washers started below the same amount of energy used by dishwashers on standard cycle. But more profligate hand-washers used up to 8 times this amount.

According to Stamminger's cleanliness scale, the dishwashing machines, on average, beat the hand-washers.

The verdict

Properly stacked dishwashers use less water and are usually better on the electrical energy front compared to hand-washing.

But there are some general tips for reducing impact either way.

Always scrape your plates into the bin with a knife or fork, and avoid pre-rinsing under a running tap.

If washing by hand, use two sinks - one full of hot, sudsy water for washing, and one filled with cold water for rinsing.

For dishwashers, make sure the machine is always full before you press 'go'.

Clean the filter regularly for increased efficiency, and, if you can, bypass the drying phase by opening the door to let out air while the dishes are hot - you'll be surprised how quickly they dry.

If you're in the market for a new dishwasher, shop by the stars.