Which size wire and breaker do I need for an electric water heater?
The wire and breaker size depend on which heating elements are in your water heater. Find the watt rating for the elements. This rating is usually on a tag on the side of the water heater. It is also printed on the elements. You can find the elements on the side of the heater under a plate attached with one or two screws.
For elements up to and including 2500 watts, the minimum wire size would be 12 gauge. With 12 gauge wire, use a 20 amp breaker or fuse. For elements over 2500 watts you must use 10 gauge wire and a 30 amp breaker or fuse. It is important to match the wire size to the correct breaker or fuse. The breaker protects the wire from overheating. You can use 10 gauge wire for lower wattage water heaters. If you are running wire for a new water heater, it is a good idea to use 10 gauge so that you are covered for any water heater you might buy in the future.
You can find wire on our web site at: http://keithspecialty.com/elec.cable_wire.htm