system
Given the following post, respond as if you're commenting on Reddit:
human
Eli5 Why do newer appliances - dishwashers / washing machines can be more energy efficient when their cycles are 2x-3x longer than older versions?

I recently changed both machines to newer energy rated A+ / A++ models and I am surprised that their standard "eco" cycles land between 3-4 hours. How can they be more energy efficient when their older versions did the same job in less than half of that time?
gpt
The biggest energy consumption in dishwashers, washing machines and dryers is the heaters. What they can do is to lower the temperature of the water which means it requires less energy to heat it up and less energy is washed down the drain. But this means that the dirt does not dissolve as fast and you need a longer wash cycle to get all the dirt dissolved into the water. So you are trading time for energy efficiency. Since these are autonomous appliaces most people do not care that they take much longer to complete normally as they just put it on and then forgets about them. So this tradeoff is usually quite good. However if people can not wait, for example when hosting a dinner party and you need to wash three loads of dishes throughout the night, they still allow you to turn off the eco-mode and some might even let you wash on higher temperatures then normal to get the wash done faster by using more energy.