As a homeowner (and end user) I can't stand Navien. Their support is awful. We just moved into our house six month ago, and the tankless unit is less than four years old. We realized that it took a long time to get hot water ' over four minutes! And or house is not very big. In fact, we have one shower right next to the water heater, and it takes over three minutes for that one to get hot. It's not conducive for washing dishes and baby bottles. And it's wasteful especially when we're in a drought. We had the annual maintenance done on the unit and the plumber informed us that our recirculation pump was shot. (The pump was shot after only 3 years of being in use). We called our home warranty company and they covered the pump for us, but it took over three weeks for Navien to get us the new pump. I should add that Navien will not speak to home owners directly, only plumbers. So any time something goes wrong with the unit, you have to call a plumber. (My husband and I are both engineers, and he works on pumps and systems at the local nuclear power plant, but Navien won't troubleshoot the issue with him). Once it was installed, we got hot water right away, for a bit ' then it quit working. There is an internal or external recirculation mode. We wanted to use the internal mode. (The external mode is great if you have an established routine, you can run it at the same time every day and you get hot water instantly. It basically keeps the water in the line hot all the time). If you're like us, with sporadic schedules, it's highly inefficient to keep the water in the external line hot all the time). The internal mode essentially heats a small reservoir (about a gallon). That water is always hot, it just takes a few seconds to get to the fixtures. We have had five different plumbers out here. First Navien said that the original plumber didn't flush/bleed the pump, so the second plumber did that. Again the water heater worked for about a day. Then Navien said the entire house needed to be flushed ' of course everything was fine with the water heater, but there might be debris in the line. So we spent over $500 to flush our system. The water heater worked for a few hours. The water will get hot, but then it won't stay hot at all. So a shower will use a gallon of hot water, then it goes lukewarm at best. Basically we have a 1 gallon water heater. Then it won't keep heating the water. Today the plumber came out (6th time) and did the troubleshooting with Navien. Navien recommended using the recirculation pump in the external mode. So we have that set to run all day. It turns on every few minutes ' I'm no expert but it can't be efficient at all. No one is able to tell us why the water heater won't work properly with the internal recircation mode. Also, no one will tell us why we can't get hot water if the recirculation pump isn't working or turned on. Before we had anyone fix the pump we could get hot water ' it just took a really long time.