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how big of service can I put in garage

scottgryffinrowyn's picture

I have a 100 amp  service in my house and want to run power to a sub pannel in my garage and I'm wondering how big of service I can make it. I was thinking of a 40 or 60 amp service, would this be possible? I live in house that has 2 2 bedroom units (each unit is approx 750 sq'). The units share the gas furnace, electric hot water tank and washer and dryer. The garage is one car (12x20), insulated with a small 4.5' high attic above, for storage that I will heat with a 1000w baseboard heater. The main garage area will be used for storage and as a hobby woodworking shop. Not sure yet how I'll heat it but I may just use a construction heater (240v) when I'm in the garage. In the future I would like to be able to run a welder and will most likely need at max a 220v 30 amp plug. Any comments from folks are most appreciated. I live in Vancouver BC.

Legally you can put a 100a (post #207167, reply #1 of 4)

Legally you can put a 100a feeder out there but from a practical sense you really need to do a load calculation to see where you are and what you can add.

There are some load calc Excel templates floating around on the internet


You should   consider (post #207167, reply #2 of 4)

You should   consider upgrading your service to 200 amp, or more. It may not be a huge expense and it will give you the extra capacity to add what you want. When we upgraded my house the power company determined that the cable feeder was already large enough so there was no charge from them. The only expense then was the new panel, ground rods, and the electricians time which was only about four hours. Oh, the permit fee was also an expense... about $100 I think. Not bad.

Normally I am capable of doing all the electrical work on my house and I could have done this upgrade. But I wanted to have it all done, turnkey, in one day. Whereas I must think through every step and take a couple of extra trips to the parts store, the electrician had all the experience, knew what the inspector would look at, and had all the extra gee-gaws in his van. His fee was money well spent as far as I'm concerned. We had lights that night.

My next-door neighbor just (post #207167, reply #3 of 4)

My next-door neighbor just had a separate service installed to his "Garage Mahal"/mancave.

Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

Depending on the layout, (post #207167, reply #4 of 4)

Depending on the layout, another option is to put the 200a in the garage and feed the house back with 100a.

It does have the advantage of being able to build the garage service, dig the feeder etc at your liesure and swing everything over in a fairly short time.

When I did it the electrician was hooking up the feeder to the house while the PoCo swung over the service. They moved the meter and off we went.

The most time consuming thing was separating the neutral and ground wires in the house onto the new ground bus..