In North American kitchens, the dishwasher is almost a standard feature. After finishing a meal, pots and dishes are stuffed into it, and with a push of a button, one can go do something else. This process may seem effortless, but it leaves many people wondering – it takes two to three hours per cycle, slower than washing by hand in front of the sink, so why do we rely on it more? And does it save water or waste it?
According to the official explanation from the American appliance brand Whirlpool, as per the regulations of the National Sanitation Foundation, the water temperature in the dishwasher must be heated to at least 65.5 degrees Celsius (150 degrees Fahrenheit) to effectively sterilize. If the extra sterilization mode is activated, the entire process can be extended by up to 1.5 hours. In other words, the dishwasher is not “slow”, but it needs to heat the water to a temperature that is unbearable for human hands, and through repeated spraying, soaking, and high-temperature drying, this process itself takes time.
In a national survey on residential energy consumption in 2015 by the US Energy Information Administration (EIA), slightly over half (54%) of American households have a dishwasher and use it at least once a week. At that time, there were around 80 million households in the US with dishwashers, but about 16 million of them hardly ever used it, nearly 20%. This indicates that dishwashers are indeed prevalent in American households, but having a dishwasher does not necessarily mean it is used daily. Some families still prefer to hand wash or only use the dishwasher as a drying rack.
Adam Norris, a senior manager responsible for the dishwasher and washing machine product line at the British appliance brand Hotpoint, pointed out in an interview with the UK lifestyle magazine “Woman&Home” that the common belief that dishwashers are more water-intensive than hand washing is a misconception. In reality, modern dishwashers use approximately 14 liters of water for a standard cycle, and as little as 10 liters in eco mode, while hand washing the same amount of dishes can consume up to 100 liters of water.
The Energy Star certification program, led by the US Environmental Protection Agency (EPA), also supports a similar conclusion: a new dishwasher certified by Energy Star uses less than half the electricity of hand washing and can save up to 8,400 gallons of water per year.
The hygiene benefits are also evident. Norris explained that the dishwasher’s water temperature can reach at least 60 degrees Celsius, far exceeding the threshold needed for sterilization. In comparison, according to the Health and Safety Executive guidelines in the UK, domestic hot water should not exceed 44 degrees Celsius to prevent scalds – meaning the temperature tolerable by human hands naturally falls nearly 20 degrees below the temperature required for sterilization, a physical limit that hand washing cannot overcome.
A study from the University of Michigan published in the journal “Environmental Research Communications” found that in most cases, the greenhouse gas emissions and water consumption from using a dishwasher are less than half of those from hand washing. However, it’s worth noting that part of the funding for this study came from the dishwasher manufacturer Whirlpool, suggesting potential conflict of interest.
As for convenience, expert endorsement is not needed – simply load the dishes, add a detergent tab, press the button, and the next two to three hours are completely freed up to do other things. Some people half-jokingly say that the biggest contribution of dishwashers is reducing the common household friction of “who’s doing the dishes today” to just “who’s responsible for loading the dishes today,” easing tensions.
(For more reading:
10 things you should never do when washing dishes – Quickly check if you’re making mistakes)
(Note: The University of Michigan study was reported by Popular Science and originally published in the journal “Environmental Research Communications,” with funding from Whirlpool.)