I still remember our first dishwasher back in the late 70's - it was an electricity and water sucking noisy monstrosity taking up a good chunk of the kitchen - and it didn't even really do a very good job.

Much has changed in dishwashers in recent years - they use less water, less juice; are lighter, whisper quiet and far less obtrusive.. and they actually clean the dishes.

We recently purchased a new dishwasher after a lengthy interlude between machines. Needless to say, the family were keen on getting another dishwasher after 2 years without one. I managed to avoid the chore by washing dishes by hand badly. Did I do it on purpose? I'll never tell :).

I've been really impressed with the model that was chosen by the family. It has a 3.5 Star energy rating (266 kWh per year) and a 4 Star water rating (13.6 Litres per wash - about 3.6 gallons). It takes care of the dishes for a day for a family of four in a single cycle.

We'd likely use more water than that when hand washing. It was a little difficult to figure out if there's any electricity or gas saving when it comes to heating the water and general operation, but to heat water and then store it takes quite a bit of energy if you have a standard hot water system. Even a tankless water system is the same sort of principle as what a dishwasher uses anyway - our model doesn't use hot water from our system; it does the heating itself, so I suspect it would be highly efficient.

The topic has intrigued me, so I went hunting around for studies.

According to a 2004 study from the University of Bonn in Germany (Household Technology department):

"If you can afford an automatic dishwasher, use one - preferably a new one. A full, energy efficient dishwasher cleans best and has the lowest environmental impact of any method".

The Bonn research determined that an automatic dishwasher only uses 50% of the energy and a small fraction of the water, along with less soap.

However, on pondering all this a few "gotchas" came to mind that also need to be considered:

- A minor gotcha - dishwashing machine detergent tends to be more harsh on the environment and earth friendly options are fewer in some places - we're still looking around for a suitable product readily available - they seem to be more easily obtained in the USA from companies such as Ecover, Seventh Generation, Earth Friendly and Trader Joe's.

- It would take a lot of energy and resources to make a dishwasher - steel, plastic, packaging, freight etc; whereas the tools for hand washing are simple and ready made - your hands :).

- The Bonn study project partners were dishwasher manufacturers. That doesn't mean to say it was overly biased, but it's always something to consider when reading studies - the level of partner involvement and what their vested interest was.

So, I'm still in two minds about the long term environmental impact of our purchase. If the dishwasher lasts for many years, perhaps it was a "greener" choice for the task when the water and energy savings are taken into consideration. Here's hoping it does because it was certainly a lot more expensive than my family washing by hand :).

I guess another way to look at it was if the time you save in washing dishes you put towards environment oriented activities, or it meant that it gave you the extra time so that you could minimize the environmental footprint in other areas of your life; that might provide some (shakey) justification :).

One thing I do certainly advise - don't cut corners when selecting a dishwasher; spend the cash on a good one - shop around and read reviews from consumer organizations and take special note of energy star and water ratings - you'll certainly notice the difference in quality, energy and water consumption in most cases by spending a bit extra. A cheap dishwasher may also wind up in landfill a lot quicker - and that's certainly not good for your wallet; or the environment.