I'm a week late with this post, but never mind.
Last week's topic on that little bit greener blog was water conservation.
A few years ago, our family invested in a dishwasher. At the time, I felt some environmental guilt about this, even though it was an A-rated appliance, because I had the impression that dishwashers used a lot of energy and water. Still, a lot of our personal energy was being wasted, standing over the sink. And certainly I never realised how much time was involved in washing up, until my evenings were liberated by not having to do it.
Since then, I've discovered that actually a dishwasher is a good thing, environmentally speaking, compared to washing up by hand. Apparently a day's washing up by hand typically uses 20 gallons of water, whereas a modern dishwasher uses less than 8 gallons. Look here if you want to read more http://shiftyourhabit.com/truth-or-trash/compared-to-hand-washing-dishes-using-the-dishwasher-not-only-consumes-less-water-but-is-more-energy-efficient-as-well/
I'm not sure our dishwasher is quite as wonderful as all that, even though we routinely use the economy setting, because it is several years old now, and new ones are probably more energy efficient.
I also suppose it depends on how many people live in your household, and how much washing-up is actually generated. We are a family of four at home, and run the full machine once a day (except when I've had a baking session, when I might need to run a second load.)