How to take an external connection from the main supply?


I am thinking of expanding my garage to a two new separated garage with workshop space. I might need two single-phase 240V and 120V circuits in the garage; I believe a 100A panel would be enough.

I have an external service panel with an electric meter outside my house. A 200A main breaker supplies to a 200A sub-panel located in my storeroom where all the house breakers are.

I want to use this outer 200A panel to supply a new circuit to a sub-panel placed in the new garage, but I can't take it into the underground because of the pool and septic system.

I thought of doing this myself with a little help from my electrical service contractors. Is there any reason I shouldn't do this on my own? If so, is there any reason I shouldn't use the existing exterior 200A service panel to supply my new garage?

Any help is welcomed!

Thanks for your advice.

  13 answers
  • Cheryl A Cheryl A on Jun 30, 2020


    Although you seem like you know what you want to do and how to do it, working with electrical is dangerous and also if it is not inspected after the work is done, you risk a fire and your insurance would not pay off if you didn't have licensed contractors doing the work - I know is true many states - not worth the risk to do it yourself

  • GrandmasHouseDIY GrandmasHouseDIY on Jun 30, 2020

    I did all of my electrical in my home EXCEPT installing the new panels (which I supplied and purchased myself) and having the new panels installed. One was my main 200 amp power to the house and then a subpanel off of that to the basement. That much power just makes me nervous honestly.

    To get power later to my garage I called an electrician and asked for their ideas. They ran four 20 amp lines underground from my power pole to my garage and put in four outlets for me on the outside of the building. From there I ran my lines. The four breakers are on my pole.

    Cost about $500 - a lot less cost than another panel and from the outlets I ran all of my own lines in the building wherever I wanted them. They chose to go underground because of trees but they definitely would have done an above ground line to the peak of the garage if it was less costly than underground.

  • If you want to be your own contractor and pull all the required permits and stick to an inspection schedule, go for it.

    However most if not all insurance companies will not cover any damage if you do the work yourself. Pull out your homeowners insurance policy or call your agent or broker.

    All work must be performed by professionally licensed contractors. Here in CA we have the Contractors State License Board (CSLB for short.) Every state has their own version of this.

    Hopefully your current electrical contractor fits into that category.

    My vote is to hire out and follow current building code in your state. Get a full price quote written estimate first so you are not slammed with a bill you can't afford. I suggest obtaining at least 3 written quotes for exactly the same work so you can easily compare bids.

  • William William on Jun 30, 2020

    Your dealing with high and low voltage. Your main panel may not work with another subpanel connected to it. Some codes do not allow overhead power lines form house to garage. Hire an electrician or ask for advice.

  • Mogie Mogie on Jun 30, 2020

    Agree with Naomie and think about hiring a pro for this. Just certain things that you shouldn't DIY if you aren't experienced with it. Just something I learned the HARD way. Best of luck on whatever you decide on.

  • Agnes Chrzanowska Agnes Chrzanowska on Jun 30, 2020

    agree with William ! It has to be done with high and low voltage

  • Ellis Ellis on Jun 30, 2020

    You should hire a contractor. This is a job where you will need permits, and most municipalities require a licensed electrician. Also, as Naomie said, you will need that proof for your insurance company and if you should ever sell your house. Just too much can go wrong with electrical work.

  • I personally would not do this on my own. Anything involving electricity could go way wrong very quick. Plus, electricity is a math game; you don't want to overload panels. I'd recommend be safer than sorry and go with a pro.

  • Lifestyles Homes Lifestyles Homes on Jul 02, 2020

    You can certainly tell your bidding electricians, that you will buy all supplies and go pull the permit, to help keep the prices down.

    Having had a $100K electrical fire, I can assure you that insurance companies will do anything to not only deny coverage, but also "blackball" a client.

  • Kmdreamer Kmdreamer on Jul 02, 2020

    Yes you could run off that panel but do put 200 in garage to you could also go over head with the wires.

  • Cynthia H Cynthia H on Jul 04, 2020

    Honestly, where we live, it wouldn't be allowed. Make sure you are following local regulations and will pass an inspection. Good luck and stay safe!

  • Betsy Betsy on Jul 04, 2020

    Hi Nellie: Unless you are an experienced electrician, I'd hire someone to do this for you. Also, they need to pull the permit, otherwise if you do and something goes pear shaped, your insurance won't cover it because you pulled the permit. Whomever pulls the permit is saying that THEY are doing the work, so unless you are experienced, never pull the permit, and if a company says they will save you money if you pull it, tell them to take a hike. Also, you will most likely need to pull a permit for your new garage/expansion, and the city would be involved in every aspect of the building/expansion. And, additionally, your taxes will increase :( Don't mean to rain on your parade, but just want to give you an umbrella :) Good luck

  • Deb K Deb K on Jul 05, 2020

    Hello Nellie, you can do what you need, but I would hire an electrician to run the wiring properly for you, better safe than sorry