when we replaced our old 100 gal gas heater at our farm with three gas tankless we saved alot of propane. So much that our propane guy accused me of having someone else top off the tank between his trips. In home the tankless take time to get hot water. They advertise instant hot but it's not. The flow has to turn the burner on, then the burner has to get hot, then your water gets hot. It can take sometimes ten seconds before water at the sink is full on hot, even longer if your a long way from the heater. The advantage is you'll never run out of hot because it can keep up to big flow rates. We have rinia(sp?) at the farm and Noritz at my folks house. The Noritz is supposed to have a higher quality copper in the heat exchanger, according to the guy selling the Noritz That being said I like tankless.