Installing electricity to an outdoor shed will likely require some amount of drilling and digging in addition to the actual wiring. Depending on the level of finish in the outdoor shed, the job may also call for the modification of drywall. Whatever the layout of your home, wiring an outdoor shed calls for working both indoors and outdoors, but upon completion you will end up with a lit and/or powered shed.
Step 1 - Make a Path from Main Circuit Panel to Outside
You may have to drill through the foundation or underneath a porch, but you need to be able to run wire from the breaker to an outdoor conduit.
Step 2 - Attach a 60 amp Breaker
To give the shed 240v power from which you can control various 20 amp circuits to power lights, outlets, etc., start by wiring a 60 amp circuit panel to the main breaker. Make certain the breakers you are working with are turned off before you start wiring. Once in place, from that breaker run 6 gauge Romex cable through the path to outside.
Step 3 - Run the Underground Conduit
The best way to run cable from a house to a shed is to go underground. Digging a trench is easy enough in which to lay conduit, but if you have to go underneath a walkway, use a piece of diagonally-cut PVC. Dig a trench 8 inches down on one side of the walkway. Stick the pointed end of the PVC perpendicular to the path and pound it, a few inches at a time with the sledgehammer. Pull it out and empty it of soil by running a thinner piece of PVC through it. Do this until the hole under the walkway is complete.
Step 4 - Lay the Entire Conduit
Lay out the full length of conduit from where the wire exits the house to where it enter the shed. Use an unbroken length of PVC. The pipe should be sealed at both its exit and entry points to prevent moisture from getting into the pipe. Refill the trench, ensuring the backfill consists only of soil.
Step 5 - Attach the Mini Panel
With the 6-gauge wire from the main circuit panel ran to the shed, install a mini panel in the shed. This will ultimately receive power from the home’s main panel, but it will power smaller 20 amp circuits in the shed.
Step 6 - Wire 20 amp Circuit Breaker(s)
Depending on the power needs for the shed, wire one or more 20 amp breakers to the mini panel. These 20 amp breakers will be used to supply power to lights and outlets. Generators, heaters or big power tools should have their own circuit.
Step 7 - Attach Boxes and Wire Everything
With the 20 amp breakers in place, attach the light and outlet boxes to the shed’s studs and run 12/3 Romex to the outlets and 14/3 Romex to the lights. Wire all of the receptacles.
With power supplied to your outdoor shed, you can now turn it into a small shop, complete with lights, power outlets and possibly a heater or a generator.