Talk me into 100A wiring vs 50A wiring

[jerry33]

The four main reason for 100 amp wiring:

1. Your TOU is short so you need to charge quickly to get the lowest rate.
2. Charging multiple cars.
3. Future proofing.
4. Listing your location on PlugShare as a charging spot.

 

[jerry33]

If your house and electrical usage is "typical", I would be skeptical if 200A service would be sufficient for much more than charging with a single 50A connection. Consider continuous loads simultaneously: A/C: 40A + AHU 20A + Oven 30A + Stove 30A + Dryer 30A + Washer 20A = 170A -- 80% of that (rated usage compared to breaker) is 136A; lighting and plugs then maybe 20A combined, and there's not much left.

For my installation, I had to upgrade utility service to 400A (two separate 200A meters) in order to run a 100A circuit for HPWC.

We charge two EVs and have all the other items, but the EVs charge at night (they finish about the time we are ready to leave) so the kitchen appliances don't enter into the load. The 50 amp A/C doesn't run as much at night as it does in the daytime (and where we live it's on the warm side).

Appliances cycle on and off, they are not continuous, so the load is lighter than the numbers would indicate. And, yes, the cooktop is 50 amps, but that's only if all five induction coils are working on high. More typical is two or three with only one on high so perhaps 15-20 amps is actually used.

 

[Drucifer]

Now for my "not helpful" answer.

I am building a detached garage with separate 200 Amp service from the 200 Amp service that my 3700 sqft house has, and am doing 2 NEMA 14-50 circuits.

1 circuit will be used for re-mounting my GE Wattstation, that actually is a 32 Amp 6.6kW EVSE.
1 circuit will be used for the UMC that comes with the car.

I already have an outside EVSE that I use on my Model S that is only 16 Amp (on a 20 Amp circuit) that I got for my prior Chevy Volt 5 years ago, that will remain in place.

I see zero reason for a single 100 Amp unit, unless you get paired HPWCs that have smart sharing on the one circuit, which for your use case might be the best idea of all.

 

[bhzmark]

It's all about marginal cost. If it's only $5 extra to go with 100 amps, then do that. If it's $1000 extra to do a 100 amps it's probably not worth it.

I would put the line at about $250 as charging above 50 amps has been rarely necessary, but still useful the occasional time that it happens. Without the ability now (or in the future?) to charge one car at more than 50, that makes it even less useful.

 

[bigdaddie]

We installed 100A at our current house so we could reasonably charge 2 BEVs simultaneously.

I did the same thing. I did the install of a 100A circuit. Pulling 3ga wire is a pain and I had to be creative to make room in my panel. The extra work is probably worth it as you can load share multiple wall chargers on that same circuit. Good deal if you have 2 cars.

 

[RandyS]

How about a compromise where you wire each HPWC for a 50 amp connection like you envision, but have the electrician use larger conduit that will accomodate larger wire down the road so it will be easy to increase the size of the circuit in the future...

 

[jimmyz80]

How about a compromise where you wire each HPWC for a 50 amp connection like you envision, but have the electrician use larger conduit that will accomodate larger wire down the road so it will be easy to increase the size of the circuit in the future...

Well part of the reason is that I'd ideally like to keep everything inside the walls. Since one of these walls is an exterior wall that I can only assume is load bearing, I can't imagine it'd be legal or easy to run 100A rated conduit through about a dozen consecutive studs. Pulling 6/2-NM through would be doable though I believe. I'll have to see what the electrician thinks our options are for that location. I just really dislike conduit lol.

 

[timx]

Pulling 6/2-NM through

If you have mice enter your garage (who get into a wall and may be seeking heat from a warm wire, then chew on cables to make enough room to move between studs), romex without conduit for 50A+ could be a fire concern. You could put conduit outside of the wall/ceiling and box around it for a more finished look if it's worth the effort.

 

[BigMskiman]

I've one car with dual charger, a 50A Wall Connector set to delver 40A. I can charge an empty battery from mid-nite to 8am, so there's no need for anything more. Staying at destination hotels is a different matter, they ought to have the 100A in case sharing needs to happen.

 

[nwdiver]

The four main reason for 100 amp wiring:

1. Your TOU is short so you need to charge quickly to get the lowest rate.
2. Charging multiple cars.
3. Future proofing.
4. Listing your location on PlugShare as a charging spot.

AND even if you're only charging at 48A your line losses are slightly lower due to the heavier wire.

 

[dhrivnak]

In over 7 years with my Tesla there was only one time I wanted/needed to charge above 40 amps. I normally charge at 24 amps to be easier on the grid. And I still always awake with a full battery.

 

[NOLA_Mike]

Is it any cheaper/easier to consider an 80A single breaker/circuit with Power Sharing? Or 70A?

I'd lean toward the larger circuit and Power Sharing which would allow you to get the full 48A (or more) charging when needed on a single vehicle. Honestly, from someone who has had a single HPWC on a 100A circuit for two years it is overkill for my needs. If I'm truthful, 240V @ 30A is more than enough for me to get full charge overnight and good enough for my home charging needs.

 

[andrewket]

I have to be able to charge our EVs in 4 hours to make the most use of our TOU plan. As a result, I have two HPWCs at 100A each, and a LCS-20 at 20A.

Being able to charge rapidly for a quick turn around has occurred a few times, and I've made use of high amperage charging in the wild a handful of times as well. But if it wasn't for the TOU plan, the marginal cost for the upgrade probably wouldn't have been worth it.

 

[jerry33]

Is it any cheaper/easier to consider an 80A single breaker/circuit with Power Sharing? Or 70A?

The difference is the cost between the 100 amp and 70 amp is minimal and not worth the bother--assuming you don't have to upgrade the service panel. Having two runs and two HPWCs does give you a backup in case one of them fails. If you already have a backup (14-50 or the existing HPWC) then that's not an issue.

 

[bikeandsail]

Everyone and every application is different. Do the math and decide. Higher capability is like insurance only important when you need it.

 

[Rocky_H]

I don't think it's worth doing the 100A line generally. Anything over 60A requires a shutoff switch, so you can do without that if you're running 50 or 60 lines. Also, the wire runs will be cheaper. Also, it's easier to install and work with thinner wire, which may figure into electricians' estimates. Since you are using wall connectors instead of an outlet, you could consider having one or both of them being sized for 60A, rather than 50. I'm thinking you said 50 just by default, thinking of a 14-50 outlet.

In general, I think having the higher amp charger in the car can be really helpful for bridging some gaps on trips sometimes depending on where you live, but having a high capacity wall connector with a huge breaker is usually overkill for at home. Unfortunately when I ordered my car, Tesla was only offering both bundled together as one package for about $3,600, which was pretty steep, so I skipped it.

 

[JST]

Pretty much my thoughts exactly. For 100A I'd have to use the Power Sharing feature, meaning ultimately with two cars charging I'd still just be at 40A to each car (same situation as simply running 50A to each wall connector separately). The only upside of using 100A and Power Sharing is that a single car could pull a full 80A if needed. But I don't own such a car and most likely won't unless the base-model charging transitions from 48A to 80A at some point in the future.

I had a similar thought process when I installed the wiring for my car several years ago. At the time I didn't even plan to put in a HPWC, just a NEMA 14-50, so why do anything more than 50 amps? Especially because I didn't get the dual chargers (that was the upgrade at the time).

But, in the end, I figured as long as I was stringing wire I might as well string a large enough gauge to allow an upgrade to 100A should the need arise. And I'm glad I did; after about a year I caved and bought a HPWC which I wired for 100, and then a couple of years later I bought a new (used) P85 that has dual chargers.

Future proofing is a good thing. Just do it.

 

[Mike M]

Our MX 90D is arriving tomorrow and luckily so is the electrician. Considered 50 or 100 AMP options and decided on 100 AMPS. Majority of the cost was in the labor for the install, and only a few hundred dollars to upgrade to 100 AMP service (due to the cost of the 2AWG wiring vs 6 AWG) from the breaker to the wall charger. Plan to eventually get a second Tesla so did it primarily to future proof, so it made sense to go 100AMPS. Its is also nice to know with just the one Tesla, I can charge at ~50 miles per hour. Also have an already installed 14-50 NEMA plug and Clipper Creek J1772 as back up (and for our Ford CMax PHEV).

 

[FlyingCookie]

Over several nights of a P100D I was charging at 28 amps at my friend's house and wasn't having any issues... Even from 18% SOC on a P100DL it only took about 11.5 hours to get to 100% charge. I'd say leave it at 50 amps and deal with the future in the future...

 

[Jimmy 1]

Did you ever wish you had bought a smaller hard drive? I rest my case.