Tankless system takes forever to heat water

How far is the unit from the faucets?
When I had one, it was far away, and I let the water run slowly at first, just enough to trigger it to go on.

Im assuming its gas, not electric, right? Gas tankless water heaters will actually take longet to get hot water to the fixture than a tank water heater, because they have a purge time just like a furnace would, before it even lites and starts to heat the water. Now, the best way to cure this problem is to install a recirc line and pump on a timer. This will give you instant hot water when the recirc pump is running. The units we install have a pump built into them for a recirc line, and all the timing is computer controlled in the unit. However, as joypulv mentioned, if you can get used to doing it, just turn the hot water on slow for a minute or so to trigger the start up of the unit and then you should be good to go. Remember, most if not all tankless heaters have plusses and minusses, this is definatley one of the -s on most units. We will no longer install a tankless without recirc, just to many complaints, even when you explain it to them before you install it. Do know, that some units do fire up and start heating water quicker than others. What brand to you have?