The 9100SXT actually has many advances recently, but for the most part, they do so little to increase efficiency compared to how efficient the system already is. Twin alternating sensor technology is about as efficient as you can get, but is the tiny gains in efficiency worth the cost in complexity and additional purchase price? Ultra efficient systems are nothing new, the problem is the math. Once you get to a certain efficiency level, it is simply a matter of tiny little advances. The real savings in the future is going to come from using less water in the house.