BASIC ELECTRICAL WIRE SIZE
 Learning the basics of your home's electrical wire size and function is important if you've decided to incorporate any electrical work into your next remodeling project. Learning how to estimate electrical work and materials is pretty simple, once you learn what size goes where. Always check with your county or city to be sure you're legally allowed to do this work. Most states require you to hire a professional electrician for anything over simple replacement of switches and outlets ... and maybe installing a ceiling fan! If you are allowed to do other electrical jobs yourself, avoid creating problems with the inspector by understanding the wire sizes. The power that enters into your home comes from your utility company, and is measured in amps and volts. The transformer on the pole outside your home governs the power you are provided and determines the size of your service panel. Most service panels (called "breaker box" by some) are 200 amps today, but homes operated on much less in the past. Your grandparents probably had a 60 amp fuse box!  Before you begin doing any electrical projects, you should understand how amperage (amps) is related to the actual electrical wire size, defined by the term "gauge" or thickness. Wires are manufactured in different gauges to ensure they will not overheat and cause a fire hazard or lose voltage. There are 4 things that cause voltage drop. Material, Area, Length, and Temperature. Material is copper or aluminum wire. Aluminum has a higher specific resistance so there's more voltage drop per foot than copper. Area is the gauge, or thickness, of the wire. A larger gauge carries more current and has less voltage drop. Length is resistance. Longer wire means more resistance and more voltage drop. Temperature is a factor because higher temps may cause more resistance. Wires that are not heavy enough to properly carry the load to a particular item heat up because of this. Figuring Out Which Gauge is Needed First, as odd as this sounds, the smaller the gauge of the wire, the more amps the wire is able to handle. That's because as the numbers go down (ie: 16 gauge, 14, 12, 10, etc.) the wire diameter goes up. In other words, an 18 gauge wire is much smaller than a 10 gauge. This is determined by the American Wire Gauge System (AWG) and is simply the amount of current that the particular electrical wire size can safely handle without getting hot. Knowing this is important when you're trying to estimate electrical work as a part of your home improvement project. The wires behind the wall are 14 and 12 gauge and they have specific places they service. Your 14 gauge wires run from 15 amp circuits and the 12 gauge wires from 20 amp. If the 15 amp service run is over 50', however, you might want to use 12 gauge. More and more homes are built and remodeled today with 12 gauge only. Specific Wire Gauges and Their Uses
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Using aluminum wiring instead of copper means using the next larger electrical wire size on all applications. For example, a 15 amp breaker would require a 12 instead of 14 gauge. Homes today are being built without 15 amp breakers at all. 20 amp service insures no (or fewer) overloads. 
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