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Question DetailsAsked on 3/29/2018

Can I add another main breaker next to the meter base?

I want to add power to my new garage. There is room for another 100-amp breaker next to the main breakers. Can i just add another breaker and run wire out to the garage?

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1 Answer


Sometimes - not usually. The incoming service drop (the transformer and wiring from the utility to your house), the meter box, the wiring from meter box to the main breaker box, the main breaker box all have to be able to handle to total of the main breakers. Any one of those has lower rating and it needs to be upgraded. Sounds like you have a 100A main breaker now - I would guess totl installed rated service is likely 125 or 150A - so adding another 100A breaker would be an illegal overload.


Each main breaker has to be rated at not more than the distribution/breaker panel (and connecting wiring) that it protects - so the right way to address this for electrician to start at the existing panel and confirm what its design load is and that its main breaker is correctly sized. Then size the new garge panel for what loads it is expected to have (and motors over 2HP, welders, electric car chargers, electric heat are commonly driving design factors there) and size the connecting wire and maini breaker for that. Then figure out if the existing service drop, meter base, and meter base to main breaker wiring needs upsizing.


In rare cases, if only running lights and a lightly loaded utility outlet circuit out there, it might be able to come off your existing distribution/breaker panel.


You can find a LOT of previous questions with answers about adding panels or circuits, including several in the past couple of months with links to lots of other older ones, in the Home > Electrical link, under Browse Projects at lower left.  Go through the most recent ones on that subject - should not have to go more than a few before you hit one or more with a listing of links to previous similar questions, which will have answers on sizing, panel rating factors, special considerations for heavy loads or future upgrades, and some ballpark cost numbers for different upgrades.

Here are links to a couple of them for starters:

Answered 2 years ago by LCD

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