The present invention relates to a user activated hot water heater and control system for processing hot water to hot water output locations, e.g. faucet, shower, or the like, such that temperature fluctuations and delays in hot water delivery are reduced. Additionally, the temperature of the hot water delivered is adjusted to a predetermined value determined by a user signature constructed from a potential user physical attributes such as height, weight, and the like. The user activated feature of the present invention will provide an energy savings resulting from the smart, upon demand, activation of internal and/or external recirculation systems. Additionally, in preferred embodiments incorporating tank-less water heaters, the hot water maximum temperature, T(maximum) is dependent on the preference setting or default value of the detected general category user or unique individual user. The user dictated control of hot water heater T(maximum) value will not only further increase energy savings, but additionally provide a safety feature that helps protects heat sensitive people such as children, the elderly and the like from potential water burns.