Energy efficiency and power quality issues of AC voltage controllers in instant water heaters

Instant water heaters constitute a significant share of the electrical load in many households. Typical heaters have manually selectable discrete power settings to match the desired temperature. Such systems may however consume more energy than required, by operating above the temperature command. On the other hand, switch-mode AC voltage controllers can provide continuous adjustment of output power and have better temperature regulation capabilities when controlled in closed-loop mode. However, the switching operations distort the line current and incur power losses. This paper investigates the use of such controllers and examines their effects on temperature regulation, energy consumption and power quality.