In regards to saving water, there can be huge benefits to doing so. I'm on the Utility Board overseeing the municipal utilities for my city (electricity, water, wastewater, trash). Our city is growing rapidly, and expanding a sewage system is extremely expensive. We're a city of ~60k and are spending ~$200mm to expand our wastewater treatment plants. And densification means current sewage lines can't support the buildings that need to be built.

More efficient appliances mean less water going through the sewer, and less wastewater that needs to be treated. Which means lower capital expenditures, which eventually come directly out of your pocket.