On-demand water heaters

My impression is that how the tankless system is installed makes for better results. We have a Truma AquaGo and so far it has been pretty good. We have about 50 days of use so far on the new rig so I may have a different opinion in a year or two. Our system does have two recirculating loops; one to the kitchen and one to the bath. When the control is turned to normal, the heater starts and shuts off when the temperature rises in the loops. This provides near instant hot water and almost no waste. If hot water use is anticipated, normal is selected and hot water is ready in a minute or two. The Truma is so quiet that you have to stand right next to it to even detect that it is on, unlike the jet plane roar of the water heater in our previous motorhome. There is an Eco mode that maintains a minimum temperature in the system which is advisable in cold weather. Forgetting to switch to Eco mode will leave the heater to cycle on and off to keep the water hot in the lines wasting fuel and consuming battery power when dry camping. The true test is the shower. Previously, I had a heck of a time getting the water to the right temperature. Trying to conserve water by using the switch on the shower handle just caused the cold water to back up into the hot water line. Turning on the water again, you had to let it run for the hot water to come back. Now, once the single handle faucet is set to the right temp, I can control the flow from off to full flow and the temperature remains constant with no waste down the drain. With a water connection and the grey tank open, I could have hot water until the propane tank runs out. There was one issue so far. The pilot light on the control knob started flashing to indicate a fault. The fault code can be retrieved by observing the pilot light on the water heater with the door open. The fault code was not in the book, so I contacted Truma by email and they told me that the fault code I read indicated a program error in the control module. They sent me a new one which took all of five minutes to swap out. The old unit was returned in the provided shipping box. The Truma is expensive, however if it continues to perform as it has so far, I would not hesitate to recommend it on a new RV or as a replacement for a conventional heater. I would qualify that recommendation by saying that the recirculating feature is a must have to avoid water waste and to have consistent temperatures. There does have to be a minimum water flow before the heater kicks in, so without the recirculating system feature, there is no distinct advantage over a conventional heater.