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Installing A Sub-Panel In A Detached Garage

July 20, 2006

Q: I have a detached garage approximately 35 feet from my house. I want to install electricity to it but, I’m not sure how much. How many volts should I install?

A: The voltage is just part of the question. You need to determine what you want to do in your garage to determine the amperage.

If you only plan to use it for hobbies then you probably only need one or two 120 volt circuits at 20 amps and GFCI protected.

If you plan to do any welding or need a larger air compressor I would install 220 volts at 100 amps.

The biggest thing you need to do is plan what you intend to do in your garage and then install power that exceeds your plans.

Installing a 100 amp sub-panel will allow for plenty of future changes or additions, but it will cost considerably more than installing a couple of 120 volt / 20 amp circuits. However, the 120 volt circuits do not allow for any future growth or changes.


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19 Responses to “Installing A Sub-Panel In A Detached Garage”

  1. Ron Sullivan on July 25th, 2006 12:54 pm

    What size wire and how many conductor do I use to run 200 amp from my meter socket to my 200 amp main breaker my pole barn ?

  2. Dewey Barnes on October 20th, 2006 9:10 pm

    I need to install a sub-panel off my main house panel, to provide a 220/240v 30amp circuit for my attached garage, which will be sufficient to provide power to two 30a/240v plugs. Could you tell me, preferably with diagrams, how to do this? I have a good knowledge of basic electricity and reading schematics and elecrtical diagrams.

  3. Gene on December 13th, 2006 6:04 pm

    I am in the process of upgrading my garage to convert it to a woodworking shop. I’ve installed a 100 amp breaker that gives me 6 circuits. My question is, what size of wire do I need to it from my house? I am not planning on doing any welding, just woodworking projects w/ an air compressor.
    appreciate any advise you can share w/ me.


  4. Administrator on December 15th, 2006 5:40 am

    Hello Gene,

    Thank you for your question.

    The size wire to feed a 100 amp depends alot upon how you are going to feed your panel.

    If you have an attached garage and you can feed your garage panel inside of your home, I recommend # 1 SER cable. This is aluminum wires and relatively inexpensive. However, this can only be used indoors.

    If you are going to supply power overhead, I recommend # 4 triplex. This will require you to do your grounding at the garage.

    If you are going to bury the wire, I recommend # 1 URD or larger with a # 4 USE ground.

    Your electrical panels are the most important part of your electrical system. These need to be wired correctly to ensure safety and that your breakers will trip. I recommend hiring a qualified or licensed electrican to do this work.

  5. larry smith on January 17th, 2007 2:20 am

    im going to run 220 to my garage,two wires will be hot and a neutral,im going to run the outlets using one hot side and a neutral and the lights using the other hot wire and a neutral,at the 220 outlet i will have two hots,will the third wire be a neutral or ground?

  6. larry smith on January 17th, 2007 2:47 am

    my garage is only 5 feet away and will only be runing a 220 air conditioner,what is the smalest size wire i can run to the load center from the house?

  7. Administrator on January 18th, 2007 5:15 pm

    Hello Larry,

    Thank you for your electrical question.

    I created a new post with your answers. Please click on the link below to see the answer to your electrical questions.

  8. Electrophoresis on March 24th, 2007 12:12 pm

    I am running electricity in my backyard to a detached garage, how deep does it need to be? If I have a sidewalk, will it be okay to bury it below the concrete?

  9. Administrator on March 25th, 2007 11:01 am

    Hello Electrophoresis,

    Thank you for your electrical question.

    The burial depth depends on numerous variables. Cover requirements are found in the National Electrical Code (NEC) table 300.5. You may purchase the NEC at your local book store or we sell the NEC in 3 different formats on our website.

    I’m going to assume you are going to install direct burial cable or conduit and wire across your lawn and under a sidewalk to the garage.

    Non GFCI protected 120/240 volt direct burial cable needs to be 24″ deep. PVC conduit needs to be 18″ deep. If the run goes under your driveway, it needs to be in schedule 80 PVC and 24″ deep.

    The direct burial cable is going to be the cheapest. However, the conduit will allow you to pull new or larger wire in the future without digging another trench. Direct burial wire cannot be installed in rocky soil.

    Yes it is ok to install your conduit or direct burial cable below the concrete.

  10. CJ on November 15th, 2008 2:39 pm

    I am running a sub-panel to my garage that is attached and I was told to run SER-4. I have already run it approximately 70 feet, and left about 5 feet at either end to connect it to the main and sub. I wanted to know if that could handle a 100 amp 220 volts circuit…?

  11. Joe Garritano on March 14th, 2009 2:09 pm

    Is there a device to install across the buss bars of a 200 amp panel other than a breaker, that will give me two Lugs that I can tap to a 100 amp sub panel with a main in the sub panel for a garage. I think there is, but I don’t know what it’s called.

  12. steve talsa on July 3rd, 2009 9:03 pm

    i have just built a pole building approx 40″ from my house.
    i have 200 amp service in my house and i installed a 100 amp breaker panel in the building,
    my question is i was told i can run 2-2-4 triplex wire from my main box to my sub in the pole building? my main house breaker box is bonded, with a green screw , so if i use 2-2-4 where will i attach the 3rd wire? to the ground lug in the sub or to the neutral lug in the sub?

  13. lee on July 13th, 2009 4:21 pm

    I want to run a sub panel to my attached garage fifty feet from the main panel which is 150 amp service what is the maximum size sub box i can run and what size wire to connect

  14. Bill Neklia on October 1st, 2009 9:40 am

    I would like to run power to my detached garage so I have power for lights, an oil furnace, table saw, drill and grinder. I have 110 amp service at the house, Can I use a 60 amp circuit breaker at the house panel to send power to the garage.
    Would I use 3#6 wire (copper) Is it a 2 pole circuit breaker?



  15. Bill n on October 20th, 2009 11:26 am

    I would like to run power to my detached garage so I have power for lights, an oil furnace, table saw, drill and grinder. I have 110 amp service at the house, Can I use a 60 amp circuit breaker at the house panel to send power to the garage.
    Would I use 3#6 wire (copper) Is it a 2 pole circuit breaker?

  16. Doug on February 5th, 2010 1:39 pm

    I am running power to my detached workshop and need some advice.
    Here’s some detail: Installing 90amp dbl breaker in main house panel for power-up at workshop. Distance: 100 ft. Plan to use #3 Cu stranded x 3 runs for power and neutral/ #8 solid Cu for ground from main panel to ground bar in sub panel. Wires to be buried 18″ in conduit. Have a Seimans 125amp external sub panel with 8 possible circuits. Will use 4 total circuits: 2 for tool power @ 20 amp; 1 for workshop lighting@ 20 amp; one for loft and external security lights @ 20 amps.
    My issue is this: I can run feeders from the main panel in conduit to my crawlspace: should I run conduit through my crawlspace as well or can I secure the wires to the floorjoists? What would you do? Crawlspace is secure. Also: how high should the bottom of the sub panel be from the floor of the workshop? It will be INSIDE the workshop – I got an external box mainly for protection of the circuits and lockability to prevent curious fingers from being hurt. Do I have a workable plan? Suggestions are always welcome! Thanks for the help!

  17. tim on March 11th, 2010 9:36 am

    I put electrical service to my garage but am getting some feedback or something to my breaker box in the garage. I ran #2 Alum. wire in conduit 100 feet . The two hot wires conected to the 100 amp breaker in the house and the 3rd wire to the nutraul bar in the house. Same in the garage breaker box. I then drove in two ground rods 6 feet apart and ran ground wife to ground stud in the garage box.
    Every thing seems to work right but when I was done for the day of wireing outlets and lights I closed the breaker box in the garage and got a tingle from it.
    Any idea’s ?

  18. Mike on July 28th, 2010 7:33 pm

    i have a 200 amp service… i need to run a 200 amp sub panel to the outside of the house for a future hot tub instulation ( which will be done by that company)… i’m wondering what type of wire is recommended and what type box for the sub panel… the wiring will be run from the main panel through the basement rafters and punched through the wall to the outside, near the location of the future hot tub…

  19. jeremy on September 11th, 2011 6:36 pm

    hello, i was wanting someone to explain how you figure out what amperage goes in for garages and also once thats determined whats the most you can add to 40 or 60 amops for examole, how do you figure it out?