Wired blogs about Google engineer Darrell Anderson who invested in a $10,000 resource monitoring system:
The company's high-end systems provide granular data on a home's electricity, water, and gas consumption, and can compute carbon dioxide emissions from that information. Their system, part of which you can see above, can hook up to 100 types of sensors, and even allows Anderson to measure the pull from individual circuits.
While the company's standard package provides visualization options, Anderson decided to take the analysis into this own hands, logging the raw data and running it through GoogleCharts. That let him see that 25 percent of his home's energy bill was going to watering the lawn. And he got to answer the bath question.
Now, Anderson can say with confidence, "Taking a bath is roughly three times as expensive as taking a shower."
Nice but he'll have to take an awful lot of showers to recover the cost of his $10,000 toy.