The average system will give 3.8 gpm at 120 with an 80 degree rise. The thing is, there is no need to heat your shower water to 120. You can't use 120. You use it at 105-106. If you set the temp to 110, you will be right back up there at 4+ gpm, which will run two 2.5 gpm showers at the same time (2 gpm hot, the rest cold). The plumbing might not supply that, but the heater will produce it. I always ask my customers to answer honestly.. when will they be using two showers at the same time? That is the classic "magnum" mentality. "how fast will this Viper go? 150+... SWEET"Originally Posted by jadnashua
Tankless requires a different thought process. When you need more gpm, you turn down the heater. Why spend all that energy to heat it to 120, and then IMMEDIATELY cool it back off at the shower? These heaters come with remote temperature controllers. When you step into the shower, turn it down to 110 and hop in. Doing whites? turn it up to the max. Slow to fill the tub? Yes, you bet. There is no free lunch. Tankless does not deliver high volumes of hot water in a short order. I compare the tankless to the "tortoise", and the tank to the "hare". A 50 gallon tank heater will give you about 70 gallons of 120 degree water every hour. A tankless will give you (in my climate) 270.