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Which is the cheapest? The diswasher or the sink?

dishwasher vs hand washing

Believe it or not but several studies have been carried out to compare the energy and water consumption of washing up by hand with using a dishwasher. The research shows that dishwashers generally use significantly less water than washing up by hand. Whilst it is difficult to compare actual costs due to variations in washing up habits, the studies concluded that provided the dishwasher is fully loaded and the economy programme is used it will be more energy efficient than washing up by hand and therefore cheaper.

Comments and Questions

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Dishwasher v Washing Up - Ian  2011-11-17 20:12:41
Eh, not so fast. According the the Government's 2008 (Update) Study (see BNW16: A comparison of manual washing-up with a domestic dishwasher) as part of the Market Transformation Programme using a dishwasher is more water efficient if 'compared' with washing up if you are cleaning over 3 place settings. As far as energy consumption is concerned it is only more efficient when being used for over 9 settings. The water efficiency was also based on an assumption that someone doing the washing up changes the water every 1.5 settings. It acknowledges that it has made these assumptions based on no understanding of how people wash up. My own research over the last two nights revealed that whilst the dishwasher was on night before last (for over an hour) it averaged over 1 khw of electrical energy. Whilst in the 15 minutes of washing up I did last night, I used about 30 w of energy, and 1 bowl of water!
Dishwasher v Washing Up - Richard  2011-11-18 10:39:39
Hi Ian I'm sure you have a point here, peoples habits are all important. In your own research I have to correct one or two errors, and they are common mistakes, seen them many times. You cannot say it “averaged 1khw of electrical energy” in this context ( and I assume you mean kWh – kilo Watt hour). You can however have an average power consumption of the dishwasher during its cycle and this probably is 1kW. Total energy is the power delivered over a period of time. So if the dishwasher was on for 1 hour this would be 1kW multiplied by 1 hour to give 1 kWh, it it were on for 30 minutes the total energy consumption would be 0.5 kWh. For your bowl of washing up again 30w of energy does not make sense. As an example; If it takes lets say 2 litres of boiled water diluted with cold to get the perfect bowl of washing up water. Then to keep the calculation simple consider a 2 litre kettle, boiling that water. The power consumption of a powerful kettle is 3kW and it will take about 4 minutes to boil the water, it will consume 3 x 4/60 or about 0.2 kWh of energy to heat the water to fill the sink. Have a look at this link on boiling kettles http://www.which.co.uk/home-and-garden/kitchen/reviews/kettles/page/faqs/ So in energy terms to use the same as a dishwasher you would have to use 5 bowls of water, and if you are just using one, then you are using less energy. I think a full dishwasher load would be several bowls. For me, I hate washing up nearly as much as ironing, so it has to be the dishwasher or the kids! Cheers Richard