I love cooking, and I cook every day for me and my wife (home office since 2008 helps there), and I love hearing about new things. I have the book “The Science of Cooking” which was fascinating.
Some people like to think they’re super water-efficient doing the dishes, but they’re not; dishwasher saves water.
About that. I know of one study done in Europe on this, and it was paid for by dishwasher companies, and didn’t exclude outliers like the guy who used about 400L of water doing the dishes by hand.
I once measured water and power usage of me doing the dishes by hand, and it was both below what I found online for dishwashers.
If you do 2-stage cleaning (soapy hot and cold clean water), then dishwashers will be better because they don’t. Amount and source of hot water governs if you are more energy efficient. The advantage of dishwashers is that a badly used dishwasher is far more efficient than badly (= wasteful) handwashing, and even efficient handwashing is not much better than dishwashers (though I wouldn’t know how to calculate production and recycling of the dishwasher itself, not even what order of magnitude that is). Which was, as far as I remember, also in the conclusion of the study, unless there has been another one since then.
It’s plausible that handwashing uses less electricity, specially if you let the machine heat-dry the dishes. But water? If you do the comparison against a fully-loaded machine, no way. Modern machines use half the water from machines of 15 years ago, and those were already competitive against handwashing. Best case scenario for handwashing (single water bath) still uses about twice as much water. Dishwasher detergent is stronger and the machine takes longer so it has more contact time, the chemistry heavily favours using less water for the same amount of gunk to dissolve.
In your case, as you already mentioned you only cook once a day and you don’t want to degrade your high end stuff in the machine, it’s reasonable that you won’t generate dishes enough to fill the machine. If you would be using a half-loaded dishwasher then it is plausible that you would use less water handwashing, but it’s still a close call - which is why I sometimes use the machine filled 1/3 without worry.
But water?
Give me a number. I use 6-8 L of water no matter how many dishes I have. From what I read, that’s about in line with the most efficient dishwashers.
You did say earlier that you cook once a day, meal for two. When I do that, all dishes for the day take a third of the maximum load on my machine, so I could wash once every three days, therefore averaging like 3 L per day tops? You handwashing every day are spending 6-8L daily which is more than double.
If it is true that you can spend <8L for an arbitrarily large amount of dishes, though, then I guess there must be an amount of dishes that you will outperform a dishwasher. They cannot handle an infinite amount of dirt, unfortunately. If you hand wash every 7 days you will be averaging less than 1L a day which really does sound unbeatable.
When would you not use two stages? Is it an option to leave the dirty soapy dishwasher on there?
