The problem with a lot of methods of very frugal handwashing is that they don't actually do that good a job. There is some data about the resource usage of dishwashers including power, detergent and materials for the machine. I can't find a source right now (too early for me), but, if I remember right, that didn't include end of useful life data (i.e., when the machine becomes garbage) because there were too many variables.

Another common statistic that is often quoted here is that when dishwasher became prevalent, they helped prevent the spread of disease in a very noticeable way. That frugal handwashing isn't the best idea.

I do believe your water usage comparison. I only handwash party dishes (though pots, mixing bowls and knives regularly). My big dishpan holds several gallons of water all by itself.

I was one of those who posted previously about the disease issue.

Our family of five moved into a house in 1956 that had our first dishwasher. (KA) Mom remembers to this day (99 years old, now) that the frequency of colds, sniffles, etc. within the family decreased immediately. She was an excellent housekeeper. She wasn't ever careless about her hand washing....but there it is. I was only eight at the time but I remember.

IMHO, whether for sanitary, convenience, or conservation reasons.....handwashing doesn't cut it.

I've assumed this for some time, since when DH handwashes, he puts the hot on full blast and power-washes everything. ;) When he's done, it looks like a seal, otter or some other happy water mammal has been frolicking in the kitchen. Water in the sink, on the counter, on the drainboard, on the floor, on the wall....

Yup - DW have claimed this for years. My DD(now deceased) worked for the utility company and always told us this.
I also agree on decreasing illness - I know when I have to wash dishes by hand that they are never as clean as the DW.
Everything goes into the DW- including my china and crystal - I figure I am more likely to break them than the DW!
(OK - there are a few exceptions - calphalon pans - but can't use with my new induction and a few hand painted goblets)

Next step in staying healthy - eat yogurt - it decreases food borne illness! I didn't believe it until I saw a study!!!