We bought our house last December which has two gas tankless w/h’s. The only issue we’ve ever encountered is we have a 4 level row house, tanks in the basement and master bath on the top level. We have to run the water for several minutes before it gets hot, but after that you’re good to go. Main level was takes around 30 – 60 seconds to heat up. I love the fact that I can take long baths and never run out of hot water. My old townhouse ran out of water 1/2 before the tub was filled up.