The current standards for dishwashers took effect in 2013. The standards, which were based on a consensus agreement between manufacturers and efficiency advocates, specify minimum energy and water efficiency levels. The standards require that standard-size dishwashers use no more than 307 kWh per year and 5.0 gallons of water per cycle.
In 2024, DOE finalized amended standards for dishwashers based on a joint recommendation from manufacturers and efficiency advocates. The new standards for dishwashers will cost-effectively reduce energy consumption by 15% relative to the current standards while also cutting water waste. Dishwashers
It is a general problem, but what started me thinking about it was being told by my dishwasher that it would take three and a half hours to wash the dishes. That seems, judging by a quick search online, to be longer than average but still within the normal range. I have not been able to find figures online for how long dishwashers took twenty or thirty years ago but, by what I remember, it was substantially less — and the dishes ended up dry, which ours don’t.
The explanation is in the final word of the quote above, “waste”. The owners of dishwashers pay for water and power, so if making them more efficient in those dimensions was costless, did not require giving up something else, there would be no need for the Department of Energy to make the manufacturers do it. I conclude that it was not costless, that it either made dishwashers cost more or do their job less well — take longer, not dry the dishes as well, not clean them as well. Using more power or water to do a better job is not waste.
David Friedman, “Optimizing On A Single Variable”, David Friedman’s Substack, 2025-06-02.
September 20, 2025
QotD: Why modern dishwashers suck
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