> How does a dishwasher that only has to run once use more energy then one that has to be run twice?
The same way a toilet that has to be flushed twice, or more, saves water.
Exactly - we have a couple of decent, newer toilets, and they do the job, for the most part, but oftentimes need an extra flush. On the other hand, the one OLD toilet we still have (it's at least 50 years old) can flush down a hand towel and be perfectly fine (and yes, I know this is true because I prematurely flushed while I was washing it up and that old towel was gone in a flash!)
We have a newer dishwasher and I HATE it -- it takes forever, the dishes are still wet when it's done (even with the hi-heat drying cycle) and there are always a few dishes/utensils that need another run.