Wiring an Electric Water Heater

In general, hot water heaters installed in most homes are powered by a 240-volt circuit. This particular voltage is counted as dangerous as it can cause serious injury or even death. It is important that the circuit is turned off when performing wiring in an electric water heater. However, the actual work of wiring an electric hot water heater is not that hard. Here are the steps on how to wire an electric water heater.

You will need:

  1. Wire Strippers
  2. Voltage Tester
  3. Wire Connectors
  4. Screwdrivers
  5. Needlenose Pliers
  6. Romex Connector (For New Installation)
  7. Electrical Tape

Electric Water Heater


  1. If the hot water heater already exists and needs to be replaced, the circuit is already present at the site. However, if you need to change over a gas-heated unit, you will need to do the circuit by yourself.
  2. You will need a 10-2 NM cable, 30-amp and a two pole to run for your circuit. It is important not to fill the tank with water until the tank is wired up. Make sure not to turn the circuit when the tank is not filled with water afterward.
  3. Depending on the type, the junction box cover where the connections will be made is placed on the top of the side of the hot water heater. Remove the cover by unscrewing the screws. You will see two lead wires and a ground screw inside the box.
  4. Use the voltage testers to make sure that the circuit is OFF before the wiring begins. Remove the knockout on the junction box with a needlenose plier.
  5. Strip the plastic outer sheath of the NM cable to about six inches of wire is exposed if the installation is new. Remove ¾ inch of insulation from each of the individual wires using wire strippers.
  6. Next, insert the wires through the Romex connector and then tighten the clamp screws. This will tighten the clamp over the sheathed section of the NM cable without exposing the wires.
  7. Insert the wires through the knockout and secure the Romex connector to the junction box using the available lock nut.
  8. Then, wrap the ground wire around the ground screw. Secure it by tightening it down. Twist the black wire from the feed circuit together with one wire from the water heater.
  9. Use a wire connector to secure the twists and wrap the electrical tape around the connections for safety. Wrap the electrical tape over its insulation with the white wire coming from the panel to identify it as the current-carrying line. Perform the same step at the breaker too. Connect it to the other wire from the water heater, the same as the black wire step.
  10. Turn the water supply back on and fill up the water heater with water after replacing the junction box cover. Turn the circuit breaker back on when the water heater is fully filled.

Image Credit:

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Additional Reading:

Solar Water Heating–Revised & Expanded Edition: A Comprehensive Guide to Solar Water and Space Heating Systems (Mother Earth News Wiser Living Series)

Convert Your Home to Solar Energy