Upgrading electrical service in an (OLD) detached Chicago garage

Upgrading electrical service in an (OLD) detached Chicago garage

I know the answer to this is, "you need to contact an electrician" but I thought I'd throw this out there.

I live in Chicago in a 110 year-old home with a detached garage. While the electrical service in the home has been fully upgraded, the two outlets in the garage are very old with their own separate fuse box. (And I am sure with old wiring).

So, can anyone comment on what might be involved in getting my garage Tesla-ready?

jat | 29 januar 2013

Yeah, I don't know that anyone is going to be able to provide much help without knowing the details of what you have now. If your main service has been updated (presumably 200A?), then likely the worst you would need would be replacing the fuse box in the garage and running new wires to it from the main breaker panel.

shop | 29 januar 2013

What breaker protection is there for the garage box? ie. usually there is going to be a breaker on the main panel that supplies electricty for the garage box. How many amps is the breaker and is it 240V or just 120V (takes up two spots or one spot, assuming regular size breakers, not quad or double ones). What does the garage box supply electricty to? It sounds odd to have a garage fuse box for just two electrical outlets, does it supply power for more things?

DonS | 29 januar 2013

Having experience working in a lot of these old houses, I'd bet the two outlets are on one circuit. Wiring is probably #12, which you should check, but that would allow a 20A circuit, or 16A actual continuous current at 110V.

One upgrade choice is to bury a 3/4" rigid pipe with #8 wires to supply a NEMA 14-50 outlet, allowing 40A continuous at 240V. Alternatively, you could install a larger run with a panel in the garage and be ready for anything you might think of in the future. I chose to install a panel fed with a 125A breaker off the main panel. This will allow me to rewire the garage, and could allow either a future HPWC, or perhaps two NEMA 14-50 outlets if I were to ever get a second EV.

Total material cost was $1300, and would have been about half with jut the outlet. Cost of copper wire is most of the difference. You could also choose a 70A or 100A garage panel depending on what you think your maximum future need will be.

Sudre_ | 29 januar 2013

My approach was similar to Don S. I figured in the future I will only be adding another EV to the detached garage so I went with a 100 amp panel. I ran three 1" pvc conduits out to the garage so I will have future options.

When you say the two outlets in the garage have their own fuse box?? what does that mean? I have seen some old wiring that had a 15 or 20 amp screw in fuse and an outlet all together but that was knob and tube stuff.... which is very possible in a 110 year old house. Not a very good outlook for a BEV charging.

When I was talking to the electrical inspector in my area about power to my detached garage, he recommended going with an entirely new panel, meter and drop (additional service). That way I could track the exact cost the car was using. The upfront cost was just too steep in my opinion.

DanD | 29 januar 2013


I have a 117 year old detached garage in Trenton, NJ.

The electrical was off of a fuse box, likely circa 1960 and enough power to run a few lights and a garage door opener.

I'm renovating the first floor due to some structural issues and in an attempt to improve the overall cleanliness (putting in insulation, sheetrock and adding a 2nd garage door). The garage is big 2000 SF on two floors.

However, I'm also upgrading the electrical and that means putting in a new panel with circuit breakers.

There aren't many things I wouldn't consider doing myself but this is one of them. Plus its absolutely required by my city and I'm sure yours that an electrician get a permit before doing the work.

My existing fuses blew every time the contractors ran their compressor so I feel pretty confident the Tesla would be powering up on a wing and a prayer.

My only problem is the city's permitting process. It's taken forever (mostly because Trenton is a basket-case). However, the work isn't nearly done and my car comes Thursday the 31st.

So my advice is to get a contractor going and pulling permits sooner rather than later.

I rewired in my first floor, put in all new lights and outlets in addition to the NEMA 14-50 and the electrical panel. I'm spending $5K on electrical.

iholtzman | 29 januar 2013

In the Chicago area call Don Butler at Kapital Electric. 630-400-7386
His company has installed outlets for many Tesla owners including me. He will be able to answer all your questions.

DTsea | 30 januar 2013

I have a 105 year old house in Seattle with a 95 year old detached garage. We ran a new power line from the breaker box (60 Amp breaker) through conduit to the garage. Terminated the prior 110V circuit to garage. 240V NEMA 14-50 (40A continuous draw) connected to 50A breaker in garage panel. Garage 110 service connected to 10A breaker in garage panel.

Electrician says Seattle code is that detached building needs its own panel for disconnect in case of fire. Seemed rational to me. Also Seattle code says building cannot have two independent power feeders- hence connecting the 110 service to the garage panel.

Wasnt too bad cost wise.