A fluid heater (1, 1000) powered by an alternating current electric power source, said heater (1, 1000) comprising: a housing having at least one chamber, said housing having a fluid inlet and a fluid outlet; a plurality of electrically powered heating elements (5a - 5d), each of said plurality of heating elements (5a - 5d) positioned within a respective one of said at least one chamber for heating a flowing fluid; a power controller for controlling the connection of each of said plurality of heating elements (5a - 5d) to the AC power source; one or more fluid temperature sensors (7a - 7e) each responsive to fluid temperature at a selected location within the last one chamber; and a logic circuit for controlling a desired temperature of the flowing fluid from the fluid outlet, said logic circuit receiving temperature information from the one or more fluid temperature sensors (7a - 7e) and providing temperature information to said power controller; characterized in that said power controller is configured to connect each of said plurality of heating elements (5a - 5d) for at least one half cycle of each of the plurality of power cycle patterns defining a power level, the plurality of power levels at which said plurality of heating elements (5a - 5d) operate are selected from the group consisting of 0/2x, 12.5/2x, 25/2x, 37.5/2x, 50/2x, 62.5/2x, 75/2x, 87.5/2x, and 100/2x, wherein a numerator of each of these fractions represents the number of half cycles of an x Hz AC power source within one second during which said plurality of heating elements (5a - 5d) are powered, wherein the operation of each of said plurality of heating elements (5a - 5d) is sequentially timed to substantially reduce switching frequencies which otherwise would cause visually perceptible lighting flicker from the AC power source. a housing having at least one chamber, said housing having a fluid inlet and a fluid outlet; a plurality of electrically powered heating elements (5a - 5d), each of said plurality of heating elements (5a - 5d) positioned within a respective one of said at least one chamber for heating a flowing fluid; a power controller for controlling the connection of each of said plurality of heating elements (5a - 5d) to the AC power source; one or more fluid temperature sensors (7a - 7e) each responsive to fluid temperature at a selected location within the last one chamber; and a logic circuit for controlling a desired temperature of the flowing fluid from the fluid outlet, said logic circuit receiving temperature information from the one or more fluid temperature sensors (7a - 7e) and providing temperature information to said power controller; characterized in that said power controller is configured to connect each of said plurality of heating elements (5a - 5d) for at least one half cycle of each of the plurality of power cycle patterns defining a power level, the plurality of power levels at which said plurality of heating elements (5a - 5d) operate are selected from the group consisting of 0/2x, 12.5/2x, 25/2x, 37.5/2x, 50/2x, 62.5/2x, 75/2x, 87.5/2x, and 100/2x, wherein a numerator of each of these fractions represents the number of half cycles of an x Hz AC power source within one second during which said plurality of heating elements (5a - 5d) are powered, wherein the operation of each of said plurality of heating elements (5a - 5d) is sequentially timed to substantially reduce switching frequencies which otherwise would cause visually perceptible lighting flicker from the AC power source.