No idea. I'm more about less waste though, so that and the home renovation was what sold me. Self-install so the cost was relatively low.

http://www.hcsa.us/files/What-does-my-toilet-really-cost-me....

Just as a reference point, in SF, the first three "units" of water (748 gallons), costs $6.42/unit. Or $0.009 per gallon. After that, $0.011 per gallon.

That doesn't include things like delivery fees, sewer charges, etc.