Water Heater Element Wattage Chart

Resistance is fixed by how the element is built and does not change with voltage; wattage and current do change with voltage, because power equals current times voltage, and current equals voltage divided by resistance. At a 240 volt supply, current is watts divided by 240, and resistance is 240 squared divided by watts.

Because power scales with the square of voltage, not with voltage directly. A supply running at 220 volts instead of a clean 240 delivers only about 84 percent of an element's rated wattage, a bigger loss than the roughly 8 percent voltage drop itself suggests, since a 0.92 voltage ratio squared works out to about 0.84. A weak or undersized service, a long thin feeder run, or a house pulling heavy loads elsewhere at the same time can all shave real recovery performance off an element that is otherwise correctly rated and wired, without ever tripping a breaker or showing an obvious fault.

Recovery rate depends on the temperature rise the element has to produce, not just its wattage; the same element recovers more gallons per hour through a smaller rise, since less heat energy is needed per gallon.

A standard residential electric tank with two elements is wired non-simultaneously: the upper thermostat controls a switching contact that gives the upper element priority, and the lower element only receives power once the upper thermostat is satisfied and that contact hands control down to the lower thermostat. The two elements are never both drawing current at once under normal operation. That single fact is also why the breaker and wire for a two-element tank are sized to whichever single element is largest, not to the sum of both elements' wattage, since the circuit never has to carry both loads simultaneously.

This is also why recovering the whole tank from cold takes longer than the single-element recovery figures in the tables above might suggest: the upper element first satisfies only the top portion of the tank near its own thermostat, then hands off, and the lower element works through the remaining, larger volume on its own. The two stages add together rather than running in parallel, which any recovery-time expectation for a full cold tank should account for.

Because only one element energizes at a time, the water heater's circuit is sized to the single largest element wattage installed, using the same NEC 422.13 continuous load method as the breaker and wire chart on this site: draw is watts divided by 240, design load is draw times 1.25, and the breaker is the next standard size at or above that design load.

Yes, indirectly. The recovery tables above are built around a specific temperature rise, the gap between incoming cold water and the tank's target output temperature, not around a fixed setpoint number by itself. A tank set to 120 F drawing from 50 F groundwater is working a 70 F rise; the same tank set to 140 F on the same incoming water is working a 90 F rise, and needs noticeably more recovery time per gallon for that reason alone, independent of anything about the element itself. Reading a manufacturer's published recovery rate without checking what incoming water temperature and setpoint it assumes is a common source of a real-world recovery rate that looks slower than the spec sheet promised.

Only if two separate limits both allow it: the tank manufacturer's maximum rated element wattage for that model, printed on the tank's data plate, and the existing circuit's breaker and wire capacity from the table above. A higher wattage element draws more current at the same 240 volts, and installing one beyond either limit means either exceeding what the tank's thermostat and wiring were built for, or overloading a breaker and wire sized for the smaller element that was removed.

Match a replacement element's wattage and thread pattern to the one being removed; a different wattage changes the breaker and wire requirement covered on the breaker chart.