American Wire gauge 1/0 is commonly confused with 1 AWG wire, but 1/0 is actually one level larger. As the numbers go down, the amount of copper goes up, so to make the next size after 1 AWG, manufacturers went to 1/0, then 2/0, then 3/0 and so on. Another way to understand how 1/0 is greater than 1 AWG is to call it 0 AWG, 00 AWG, and 000 AWG.

There are many types of electrical wires and cables that a homeowner may see on a day-to-day basis, but it is rare to see something as large as a 1/0 wire or cable. Most types of electrical cables in a house are Romex® and THHN cables. THHN wire has been double rated with THWN wire for years, which added the “waterproof” approval to the insulation.

The sizes that a typical homeowner might see throughout their home are 14, 12, and 10 AWG. Those are the most common electrical wire sizes that carry power from the basement electrical box to lights, outlets, and appliances throughout the house. The amount of power output from the dryer will be much greater than the amount of power sent to a light switch due to the amount of power the dryer needs to run.

Romex® is actually meant as THHN cables, so the same cable is used, but Romex® allows electricians or installers to run more than one cable at a time in a bundle rather than individually. This speeds up the installation process, especially when a new home or building needs to be completely wired from scratch.

The homeowner doesn’t really need to understand every type of cable that is installed in their home, but it can be helpful to understand the difference in size between the cables. A THHN THWN 1/0 electrical cable would most commonly be found feeding the entire electrical box. This size of wire will run from the telephone pole to your house and to the electrical box, providing you with about 300 amps. That 300 AMPS can then be assigned to every outlet, light switch, and appliance in the entire house until all 300 AMPS has been used. At that time, a new electrical box will need to be installed to supply power to anything new you may have, such as a hot tub, garage, or barn.