What Gauge Wire Do You Use for Electric Water Heaters?

Low-Power Tank Heaters

• An average low-power tank water heater will use below 2,500 watts of power. With that wattage, many fire safety codes require a 12-gauge wire as the minimal safety requirement. This means that even at maximum draw, the wire runs no risk of overheating. As with any high-powered appliance, many codes also require that the wire used be copper, as copper is good for conductivity.

Higher-Power Tank Heaters

• Larger or higher-power tank heaters will typically use slightly more than 2,500 watts. With these larger heaters, use a 10-gauge copper wire along with a 30 amp breaker or fuse. The reason for the increased breaker is to allow for the increased electrical flow to the appliance.

Tankless Water Heaters

• Tankless water heaters draw much higher amounts of power at once to heat water as it passes a coil. In fact, many tankless heaters use around 9,500 watts of power at its highest drawing ability. In this case, a 6 to 8 gauge copper wire and a 50 to 60 amp breaker would be required. This is a general electrical guideline for the high amount of power. For optimal safety, verify the wire gauge with your local building codes.

Installation

• There are two possibilities for wire installation. You can either run the wire through your current cable sleeve if there is room. If there isn't, it's better to bury the wire underground and run it up the side of the house and against the eaves. If you do the latter, cover the wire in a PVC pipe. The pipe can be buried and secured to the home with brackets.