What size wire for a shed? (2023)

When I built my first shed years ago, I quickly decided I needed power for some lights and to run my tools. Wiring the inside of my shed was easy, but I wasn't sure what size wire to run inside a shed.

The size of cord you find in your shed will depend on how far away you are and whether you are using 120v or 240v. If your shed is within 50 feet of the fuse box, you can use 10/2 UF-B wire. AWG for a 120V circuit up to 20A. This allows you to run multiple machines at the same time and provide light to your shed.

The above circuit provides enough power for a couple of lights and a couple of 120 volt outlets. If you want to power some heavy equipment like a welder, you'll need to upgrade to a higher amperage circuit breaker and smaller wire.

Next, we'll look at all of your options for using different wire sizes, including wire types, gauges, and leads.

Fast navigation

  • What gauge wire to use for a shed
    • Which cable for 240 volts?
  • Cable size to use: Examples
  • What happens if the wire cross-section is too large?
    • Can I use too thick wire?
    • What if my cable size is too small?
  • What size shed do I need?
  • How far can 10 gauge wire go?
  • Can I use an extension cord to power my shed?
  • Do I have to bury the cable?
  • Conclusion

What size wire for a shed? (1)

What gauge wire to use for a shed

Most shed owners need a few plugs and a few lights to see what they're doing. You typically need a little over 15 amps to power your lights and a miter or table saw at the same time. Use a 20A breaker and 10/2 AWG UF-B wire.

Here's why: A 20-amp circuit breaker ensures it won't trip if you're operating your tools and lights at the same time. Heavier devices, like a miter saw, are rated for up to 16 amps. While that doesn't mean it's running at 16 amps all the time, it does indicate that you can get close to that. In combination with lighting, a 15 ampere circuit breaker is not enough. Wow 20.

Typically in your home you use 14 gauge wire with your 15 amp 120 volt breakers and 12 gauge wire with your 20 amp 120 volt breakers. So why not use 12 gauge wire for your shed?

By using 10/2 wire for your shed you can upgrade to a 30 amp circuit breaker in the future. This will prevent you from removing the 12 gauge wire from the conduit and then threading the new wire through the conduit.

(Video) Wiring a Shed or Detached Building

If you are determined never to increase your amperage, which would allow you to run an electric heater and power tools, then 12/2 AWG UF-B wire is perfectly fine. The wire is the correct gauge for a 20 amp breaker.

Which cable for 240 volts?

If you're bringing 240 volts into your shed you'll want to run something like an electric fireplace or welder. If this is the case you will need a 50 or 60 amp circuit breaker in your main sub panel.

The use of 6/3 AWG UF-B wire allows you to bury it directly into the ground and is of a gauge low enough to safely power your 240 volt shed circuit.

If you are using lower rated 240 volt appliances such as

Finally, always check the voltage and total power requirements of the device you intend to use. Remember the old formula: volts x amps = power. Not all devices are the same. While your neighbor can run a power tool on a 15 amp circuit with a 14/2 cord, that doesn't mean you can. Always read the labels first.

Cable size to use: Examples

What size wire for a shed? (2)

The longer the circuit, the less capacity that circuit has to deliver voltage; this is called "voltage drop🇧🇷 The wire gives off heat, which is essentially a loss of electricity. The longer the cable, the more heat is lost.

If you run the cord to a shed far from your home, you could experience a power outage: tools not running at full power, dim lights, etc. That's because your 120 volt circuit is more like 108 volts... Or less!

One way to compensate for this is to use a thicker gauge wire, which reduces current resistance and voltage drop. Remember, the thinner the wire, the greater the resistance and heat loss. Make the thread thicker so you have less resistance.

Let's take a look at the wire size needed to connect a circuit from the main electrical panel in your house to your shed.

Note: The following calculations are in accordance with national regulations which prescribe a 3% voltage drop as the maximum allowable loss in a circuit.

(Video) How To Wire a Shed for Electricity | Ask This Old House

  • 150 ft run: A 120 volt circuit on a 20 amp circuit breaker requires 6/2 AWG wire for 150 ft.

We have already mentioned that if your shed is supplying power to your shed from a 20 amp 120 volt circuit breaker it must use 10/2 wire. However, this only works if your shed is 85 feet or less from the breaker box.

On a 150 foot, 240 volt, 30 amp circuit, the double pole switch would require 8/3 AWG wire to power the circuit breaker.

  • 300 ft run: A 120 volt 20 amp circuit would require 4/2 AWG wire. A 240 volt 30 amp circuit would require 4/3 AWG wire.
  • 500 feet: A 120 volt, 20 amp circuit would require 1/0 AWG wire. A 240 volt 30 amp circuit would require 3/3 AWG wire.

Please note that a voltage drop of 3% is minimal. If you used an 8/2 wire to run 150 feet to a shed with a 20 amp breaker, you probably won't notice the drop. There? You would have to run multiple machines at full power at once to get 20 amps.

While I do not recommend exceeding the 3% voltage drop parameters, please understand that many people use a meter higher than prescribed by aVoltage Drop Calculatorand they see no difference in the performance of their tools or accessories.

What happens if the wire cross-section is too large?

If you go to your local hardware store, you'll find that wire comes in all shapes and sizes. You might be tempted to overcompensate when wiring your shed. For example, what if you start welding or install an electric furnace in the future? You need a bigger wire.

So you don't want to pay for a thread that's fine now, but isn't fit for future needs. Can you just run a heavier gauge wire with a lower voltage and amperage circuit?

Can I use too thick wire?

Yes, you can use a larger, oversized wire with a smaller loop. You will see no decrease or increase in circuit performance.

The only benefit is that the voltage drop in the circuit is reduced, although it's probably negligible at first.

You don't want to run your shed on 240 volts and find you need 6/3 instead of 10/3. There's nothing wrong with using a smaller gauge of wire when a larger gauge will do. Gives you room to expand without having to replace the cable.

The advantages of using a larger gauge of wire include:

  • Gives you the ability to increase the amperage of your breaker in the future without changing the wire size
  • Reduces circuit voltage drop and improves the ability of the devices in your circuit to operate at full power

What if my cable size is too small?

Using a cord that is too small for the circuit can damage the equipment, burn the cords, or cause a fire. For example, using 14 gauge wire in a 20 amp circuit will create a lot of resistance in the wires. This manifests itself as excessive heat, which can melt the insulation on the wires and cause a fire in your home or shed.

(Video) Complete Guide to Wiring Your Shed

At the very least, the cable insulation can slowly melt over time and pose a risk of electric shock. Being near insulation or other combustible objects is an extreme fire hazard.

What size shed do I need?

A shed requires different considerations than a house when it comes to power. Your shed will use electricity less frequently, but when it is in use, the performance of the powered equipment will be much higher. Saws, compressors, grinding machines - they all consume a lot of watts.

So running your shed at 15 amps is a mistake. You may not be able to use a miter saw and a light at the same time, so get a more powerful miter saw.

Use a 20Amp circuit breaker with the wiring recommended above and you can power multiple tools and lights from the same circuit.

If you need 240 volts in your shed for a larger piece of equipment like a welder, it will depend on how many watts the unit needs to use. A 30 amp circuit breaker will suffice for 240 volt appliances such as a window air conditioner. A welder will likely require a 60 amp breaker.

How far can 10 gauge wire go?

You can run 10 gauge wire up to 85 feet in a 20 amp circuit. If you use this type of wire in a 15 amp circuit, it can be as long as 115 feet. Beyond these distances, the circuit exceeds the recommended 3% voltage drop.

You can run 12 gauge wire up to 70 feet in a 15 amp circuit. That number drops to 50 feet if you run 12 gauge wire through a 20 amp circuit.

Can I use an extension cord to power my shed?

Yes, but I would not recommend itUse an extension cord to power your shedas a permanent solution.

While this is a quick and easy solution to powering your shed, the dangers of a permanent extension between your house and the shed is not a good idea, and here's why:

  1. It can tear, rip or rip.
  2. It is a danger to other people on the farm.
  3. It's inconvenient if you want to connect more than one device.
  4. You can't light your shed and use a tool at the same time.

Do I have to bury the cable?

Yes, the only type of cable you can use outdoors is the cable labeled "UF" which stands for "underground feeder". You can usually run this type of cable directly or in a conduit.

If you want to bury the cable directly into the ground, you need to dig 24 inches. If you use cable channels, 18 inches is sufficient.

(Video) Wiring A Shed

If you only run one circuit for your shed, you don't need a subpanel. However, you will need a circuit breaker where the electricity enters the shed. This could simply be a light switch that controls all the outlets and appliances in the shed.

If you have more than one circuit, you need a subpanel, which you can find explained in this articlehow to get electricity in a shed.

Conclusion

When it comes to electricity, safety is paramount. Be sure to turn off the main switch when installing a new switch in your box. Connect newly installed house wiring to the breaker box last to avoid risk of electrocution when installing wiring or outlets.

Wiring can be confusing and I hope this article has answered all of your questions about what size wire to choose for your shed. Remember never to take risks or guesses with electricity. If you still have concerns about wiring your shed or choosing a wire size, consult an electrician.

As always, thank you for taking the time to read this article. Please message me or comment below if you have any questions or would like to share your own experience of choosing a wire size for your shed.

Eugene Sokol

A handyman for most of his life, Eugene loves to be creative while inspiring the creativity of others. He has a passion for renovations, renovations and carpentry work.

(Video) INSTALLING AN ELECTRICAL SUB PANEL FOR SHED

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