What kind of electric wire to run to a shed?

Written by james stevens | 13/05/2017
What kind of electric wire to run to a shed?
You need to use the correct type of wire for outdoor use. (Jupiterimages/Photos.com/Getty Images)

If your garden shed is located away from your house, you may want to run electricity to the shed. Ensure that you use wire suitable for an outdoor environment. Consideration also needs to be given to the distance between the shed and the power source in your home. You also need to work out what type of electrical equipment you will use as the wire must be able to carry the necessary electric current safely.

Wire Sheathing

The sheathing protecting the wire is extremely important, if you are running electrical wire outside. It needs to be heat-resistant, flame-retardant and water-resistant. There are two main types of wire suitable for outdoor use: thermoplastic, heat-resistant, water-resistant, nylon (THWN) and thermoplastic, heat-resistant and water-resistant (THW). If you intend to bury the wire, you need to get underground feeder (UF) wire. Outdoor wire needs to be placed inside a protective conduit.


Amperes relate to the current that electrical equipment consumes. The wire to your shed must have an amperes rating greater than the maximum amperage draw of all the electrical equipment you intend to use in your shed. It's best to work out what equipment you may use and look on the labels of the items to find out the amperes of each. If you add the amperes together and add on an extra 20 per cent, you know you will have wire that can safely carry the required amperes and allow for a little extra.


The distance current needs to travel between the power source and the shed is important to getting the correct kind of wire. Wire creates resistance and the farther the distance, the greater the resistance. Measure the distance from your shed to the power source, then double the result.

American Wire Gauge

The American Wire Gauge (AWG) is the standard set to define the thickness of wire. It's a numerical system that runs from 0000 to 20; the higher the number, the thinner the wire, so 20 is a thin wire. To work out the gauge you need, it's necessary to know the total amperes draw and the distance. Because the variables between the two figures have a direct effect on the wire size, there is not one type of wire size. For example, if the wire needs to carry 20 amperes and the distance is 15 feet, you need AWG 10, but if the current draw is 20 amperes and the distance is 80 feet you need AWG 2. However, if you provide the two figures to a reputable electrical store clerk, he will be able to tell you the wire size needed. Alternatively, there are many websites that let you enter the two figures and automatically calculate the wire size for you.


Electrical wire has detailed information printed continuously along the outer sheathing, so you can identify it. For example, it may have UF THW 10 printed on it, meaning it is underground feeder, thermostatic, heat- and water-resistant wire, gauge 10.

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