How Do Water Heaters Work

Water heaters are essential in commercial and industrial facilities — for restrooms, break rooms, process applications, and janitorial use. Understanding how different types of water heaters work helps facility managers choose the right system and recognize when electrical service is needed.

Storage Tank Water Heaters

The most common type. An insulated tank holds a reservoir of heated water — typically 30 to 80 gallons for commercial applications, much larger for industrial use. Electric versions use one or two resistance heating elements controlled by thermostats. When hot water is drawn, cold water enters the bottom of the tank and the elements cycle on to reheat.

Electric storage water heaters typically require a dedicated 240V circuit. Large commercial units may require 3-phase power. A licensed electrician must size and install the circuit properly for the heater's rated amperage.

Tankless (On-Demand) Water Heaters

Tankless heaters heat water only when needed, eliminating standby heat losses. They're more energy-efficient for facilities with intermittent hot water demand. However, electric tankless heaters require substantial electrical capacity — whole-facility commercial units can require 150–200 amps at 240V. A full electrical assessment is essential before installing a tankless system.

Heat Pump Water Heaters

Heat pump water heaters extract heat from ambient air and transfer it to the water, using 2–3 times less electricity than conventional resistance heaters. They're ideal for facilities in warm climates like Houston with consistent ambient temperatures. They require adequate space for the heat pump unit and a standard 240V circuit.

Electrical Requirements Summary