Boston Bob's commment is correct, the instant hot water is instant at the unit itself, then drops off as the hot water runs through the house, Installing a recirculating line will help if installed correctly. A house of 2-3 this unit when installed correctly would be OK. 4 or more and the recovery time may start to suffer. A unit running for an hour running hot water may tend to fade away as the recover starts to diminish, odd as it seems it is correct. In apartments they uses a type of heater with a return line the and heater is more along the line of a pool heater. Cost affective...? I would rather buy a new 50gal $200 water heater every 7- ten years. Can you get that savings on an instant heater??? Guessing no repair cost for a 5 year warranty unit, would cost 12 cents per day for 5 years for the purchase of the heater.