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Building new garage- 100amp or 200amp service

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T

tmc2015

Member
May 24, 2015
41
1
USA
#1
Building an oversized one car garage. We are running dedicated service to then garage - it is $350 more to do 20amp service vs 100amp.

My ride doesn't have duals chargers, but I want to leave that option open. If we do 100amp service, can we run a 100amp circuit to an HPWC? Should we pay the extra just to be safe/have flexibility down the line? I don't foresee needing more capacity than 100amp, but who knows (our house was constructed in 1922 before the need for central air was conceived for example).

It is only a one car garage and there isn't much of a driveway (alley) so us having an second EV plugged in regularly is unlikely. However, I want to see if I can provide a secondary outlet on the outside of the garage for someone to use if they are in a pinch. That would be a NEMA 14-50 and I'd shut it off at the panel if I didn't want people using it. I really don't know how I can pull this off with the garage layout, but I want to be a good citizen. It really wouldn't cost much to put it in.

Inside, I have to decide on the HPWC vs NEMA 14-50. I guess I will do the latter and see if it is annoying to not have the convenience of a HPWC.
 
#3
Personally, I would..
"Future proof" the construction and go with a 200 amp service.
No one needs less electrical service in the future... it is always more!! and upgrading is twice as expensive as what ever you install.
What will you next EV need? Bigger battery and higher charger rate?
Will the future buyer appreciate the 200 amp service?
Will you want to use the space as a workshop?

The 200 amp service equipment is more robust and worth the investment.
Also have a bunch of 120/240Vac-20 amp, a couple of 240Vac-30 amp and at least one 240Vac-50 amp outlets installed along the walls inside during the construction.
If you are going to regularly charge a Tesla I would use the HPWC as it is safer (a more robust charger and set it up with 100 amp) than an UMC plugged into a NEMA 14-50.

I also would insulate and sheetrock the walls and ceiling. Compared to the slab and framing, finishing the interior is inexpensive and makes the space much more temperature stable.
If you don't use all of what is installed, it is still there for you or the next owner when it is need.
 
#4
200AMP? What in the world would you need that for (except to fast charge two teslas at once).
I know more is better, but why stop at 200? Why not 500?

Seriously, will you really ever need 200 amp?
I have a hard time justifying 100 amp :)
 
#6
kuttakamina said:
200AMP? What in the world would you need that for (except to fast charge two teslas at once).
I know more is better, but why stop at 200? Why not 500?

Seriously, will you really ever need 200 amp?
I have a hard time justifying 100 amp :)
Click to expand...

200 amp service equipment is about the same size and cost as 100 amp equipment.
400 amp equipment is 2-3 time the size and cost.
Again, with 200 amp you future proof the service but with 100 amp you will most likely want 125 amp or 150 amp for EVSE in the near future.
The HPWC is a 100% load and the 100 amp service is all but used up except the last 20 amps and you have yet to even have the garage built.
There is 100, 125, 150, 200 & 225 equipment but at that point all you are doing is selecting the main breaker and service entrance wire size as the added cost for the larger 200 amp is cheap.
However, it you want to keep it small and install the larger service if and when it is needed that works; just not the way I'd do it.
 
#7
We will never be in a position with this property layout to be charging two vehicles at the same time consistently - if we did, I wouldn't have an issue with timing or dialing back on the HPWC if we needed to make some adjustments like that or use the delay charge feature.

That said, for $350 (roughly 12% increase in cost) to provide some flexibility in the future, I'm leaning towards it. Charging overnight at 29 miles added per hour is fine now but if there is a bigger battery, etc, who knows. Honestly don't really need the HPWC at 100amp. Since the panel will be in the garage, running the wiring will be reasonable no matter what gauge. So first I will definitely do NEMA 14-50, it will cost under $20 since I already have some 6/3 wire from a 50amp second floor subpanel in the home. Then we will see how it works out and what to do next.

On adding the HPWC or an Exterior NEMA 14-50 to plug share - I will search the forums before I do anything like that but am open to hearing feedback from people who have done it. The only real reason I would pay for an exterior NEMA would be to support other EV owners. Giving access to the HPWC would mean giving access to my garage which creates additional exposure and is more of a pain for me. I could give a user the combo to a padlock on an exterior outlet or just flip the breaker for them in advance of their charge - pretty simple. Again, all of that is assuming I can figure out how to give access to an outlet where their car wouldn't be blocking the sidewalk or alley for others. They would have to block my garage door but that would be okay for occasional uses.
 
#8
Complete install included: a 14kW solar panel system along with upgrading main panel from a 200amp to a 400AMP (required utility company to bring a new feed from the street into my main panel); added a new 150amp sub-panel branched off my new 400amp main panel off into the garage where a dedicated 100amp breakers is now alloted to the HPWC for my dual charger MS while the other 50amp shared between spare a 14-50 and a 10-30 for future/alternative use. Future proof, making charging MS as fast as possible (short of a SC, of course), scalable to provide aboundant power to charge 1-2 more EV's, and still keeping the utility's power used to a minimum, this has been pricey commitment but the best way...and very happy with my investment.
 

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#9
I will also be running a new service to my garage which will hold the Tesla.
Beyond any doubt, it will be a 200 AMP service panel.
For the Tesla I will have a 100 AMP breaker feeding the HPWC using conduit and #2 copper wire.
Also for the Tesla I will have a 50 AMP breaker feeding a 10-50 outlet also using conduit.
The 10-50 will be a backup outlet should the HPWC ever fail.
Additionally, I will have a few 20 AMP 110v outlets installed on the three walls of the garage as well as the ceiling for lighting and garage door opener.

Although I anticipate very little use of the service other than the Tesla Recharging, the delta in cost for a 200 AMP service vs a 100 AMP is very minimal.
 
#10
Why not split the difference and run a 150 to the 1-car garage? That should provide plenty to an HPWC if you need the full 100 amps and then have some for your outlets, lights, saws, etc.

The bigger question should be - what is the service running to the property? Mine is only a 150, so running a 100 amp sub-panel service for my HPWC didn't make sense (plus the fact that I'm not getting the dual chargers). If your main service to the property/house is 200, then putting a 200 amp sub-panel on a 200 amp service doesn't make any sense and I doubt that meets electrical code.
 
#11
ibxspeedracer - will you share some more details on your install and how this is fed into your system? Any diagrams/brands/models/costs that you are willing to share would be appreciated - private message is fine.

chriSharek - this is new service for the garage, completely independent of the service to the house.
 
#12
For the $350 extra, do the 200. You won't regret it, and it will save you from having to upgrade to 200 later (and I'd guess there is a 90% chance that you'll do that upgrade within three years).
 
#13
Most of the things that we buy we do not "need." We want them.

100 A can feed a HPWC set to max 80 A charging. I would only use 30-50 A for overnight charging. That is plenty and it keeps the stress on the wiring and HPWC low.

However, 80 A capability would be handy if you routinely charge to 80%, and need to top off to 100% quickly to take a long trip. Also handy for visitors to charge up for their return trip.

The remaining 100 A can be used for the 14-50, and for all the other garage loads. The OP, or whoever eventually buys the property, may want more than a light bulb and a garage door opener. The 200 A service is for the entire garage, not just the car(s).

GSP
 
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#14
Gotcha GSP. I deleted my message because a search answered my question. But I see your point (I think you were replying to my message?).

here is the funny thing - the top two posts in this subforum are this, where people are overprovisioning for convenience and another where people are talking about using superchargers exclusively to save $5 of electricity.

Funny!!
 
#15
For $350, absolutely do the 200 Amp service. Remember that if you put in an HPWC on a 100 Amp breaker, there will be nothing left for the service outlets, lights, etc in the garage.

If it were me, doing a new garage, I would do 200 Amp service, install an HPWC on a 100 Amp Breaker, and a 14-50 on a 50 Amp circuit, leaving plenty of capacity left for outlets, lights, etc. Doing all the electrical during initial construction is the least expensive. The 100 Amp HPWC will be there waiting for when you upgrade to dual chargers, and is the easiest day-to-day charger, leaving the UMC in the car. On the off chance that your HPWC fails, or you want to test your UMC before a road trip, the 14-50 is there waiting for you. If you normally drive in, back out of the garage, putting the HPWC and 14-50 just inside the garage door on the left, will be convenient for you, and if a visitor arrives, you can run a cable under the garage door. If it fits, putting the circuit breaker panel and service entrance near where the HPWC and 14-50 will go, will reduce overall wiring costs.

Good Luck!
 
#16
I think it's a no-brainer. For only $350, I'd go for 200A. That extra charge will be a small fraction of the total construction cost. Upgrading later will be significantly more expensive.

Also, with only 100A, you could run into an issue with an indoor HPWC and an outside 14-50. What if you are charging at 80A and someone comes by and plugs into the outside 14-50? 100A, tripped main. 200A, no problem.

200A service will also have larger service entrance conductors, which means less voltage drop under load and (slightly) faster charging.

I'm thinking about building a 2 car detached garage; it would have it's own service as well. 200A is a minimum. I'm seriously considering going up to 320 or 400, depending on cost.
 
#17
I didn't look into more than 200 because that's the standard our electric company will pull - whether you do a 100 or 200amp panel, they bring 200 from the line. I'm guessing there would be a big cost from the electric company in addition to the electrician, but I can't speak with authority on that.

If I do the exterior outlet, it would be off or locked so there wouldn't be the random double charge scenario. Having the 14-50 inside as a starter is happening, then we will see how I modify. Putting one on the outside won't be hard either, but messing up the siding, etc, blah, we will see. This is an oversized one car so I also wouldn't be running a saw and charging my whip at the same time. I don't need more than 100amp and likely never really will, but I love flexibility/convenience which is my least favorite thing about this car.

And agreed on the earlier post on want vs need. None of us need a Tesla period.
 
#19
chriSharek said:
Why not split the difference and run a 150 to the 1-car garage? That should provide plenty to an HPWC if you need the full 100 amps and then have some for your outlets, lights, saws, etc.

The bigger question should be - what is the service running to the property? Mine is only a 150, so running a 100 amp sub-panel service for my HPWC didn't make sense (plus the fact that I'm not getting the dual chargers). If your main service to the property/house is 200, then putting a 200 amp sub-panel on a 200 amp service doesn't make any sense and I doubt that meets electrical code.
Click to expand...

In my situation, my home's outbuildings are a horse barn and 5 car garage. At present, this outbuilding complex is fed by an old 30 AMP underground feed from the house.
Nearby the barn is a utility pole. An electrician informed me that the most cost effective way to up the power to the outbuildings would be to run a new electrical service from the utility pole to the barn/garages. It is also much less disruptive. Here in CT, the utility company will run a new service for 0$ cost. The 200 AMP panel and main shutoff and wiring job (outlets and HPWC) is estimated to be about $2K vs an additional $6K to run a 100 AMP underground wire and uplift the panels in the out building. a backhoe and about 90 feet of trenching would have to be done through established perennial gardens and walkways. Not so nice a prospect in my eyes.

I had the utility company preview inspect the proposed install and the inspector stated that this was the best way to go, as my existing 200 AMP panel in the house would have to be upgraded were i to run an underground service. I am not sure if all utility companies will provide a new service for "free" but working with all new electrics for the constant duty charging of the Tesla is a benefit in my mind.
 
#20
Is there a chance you'll want a fridge, or maybe a minisplit for comfort? How about solar, might that get added?

It depends on your personality. Will $350, if overspent, bother you forever or be soon forgotten?

Do you have masochistic tendencies? Will you enjoy the inconvenience and regret if it turns out you could use it and don't have it? (Such people are less rare than one would think...)

.........

Art, your situation makes me wonder if there is a solar and Tesla powerwall opportunity...
 
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