Siemens are a well known brand name, probably more through mobile phones than anything else. Their reputation has successfully transferred to their range of kitchen appliances, including dishwashers, and microwaves.
Siemens actively try to be more environmentally friendly, and most of their non-budget machines will include features such as ecological cycles, where less water is used, and at lower temperatures. One feature also involves used hot water beign used to heat up the incoming cold water.
Since Siemens has such a reliable reputation, expect to pay more that you might for a different brand.