HPWC installation research

[Hiquan]

Hi,
I've tried some searching but have not gotten enough information.
I'm researching on how to install an hpwc at home. I do have the 72A charge option and want to take advantage of it. My main panel is 200A and is located on one side of the house, and about 75+ feet away towards the other side is the garage. Power is split, 100A for this side of the house and the other half goes through a sub panel for remaining 100A for the AC units and dryer hookup. The garage is closest to the AC units.
In order to add this new 100A line:
Will I need to upgrade my main panel to a 400A box? Approximate cost? And do I need a city permit?
Also, any idea on how to run the 100A cable to the hpwc? Dig trench around house or run some pipe to the attic and then drop down to the garage? I am approximating 75 feet for this cable run.
I have not called for quotes yet, just wanted to do some research first to get a ballpark cost.
Any feedback appreciated.

 

[JHWJR]

You sound like a do-it-yourselfer, and I respect that. But if you are asking these questions, i recommend a good electrician who has answered all of these questions 300 times and no longer has questions about it. 100 amps are not to be trifled with.

That said, I would observe that some of this is subjective and judgment calls. My discussion with my electrician went something like this:

[Looked at the panel.]
He says: "Do you have an electric stove or a gas stove?"
Me: "Gas stove."
Electrician: "You can probably put a 100 amp service on this box then. If your lights dim for a moment when charging starts, you may want to have us take a look. We could then have a larger service run from the pole. That will require that we make arrangements with the electric company to change things at the pole and probably run a larger line to the house. But let's not do that until we see whether this works well enough and it probably will."

And it has worked very well. At least, that's how I remember it.

 

[Hiquan]

I do plan to get some professional quotes for this project after I get as much information as I can. Was hoping to get some feedback on approximate cost range I should be looking at.
Thank you for your feedback so far, the dialog with your electrician gives me hope.

 

[BrettS]

Honestly, the best way to get an idea of the approximate cost range is to have a couple people come out and give you quotes. You can get numbers from what others paid, but the costs will vary considerably based on location and distance to the breaker box and where and how the wire needs to be run, etc.

In order to answer some of your questions, though, 200amp service could be enough, or it could need to be upgraded. Again, your electrician would know for sure, but if you have a lot of electric appliances (electric drier, electric stove, electric heat, electric hot water, etc) then 200amp service might be pushing it. If all those things are on at once, plus 72amps to the car you are likely to exceed your 200amp limit. If you have mainly gas appliances then you’re probably not coming close to your limit and adding 72amps for the charger should be fine.

 

[animorph]

I was able to fit a new 100A charging circuit to my 200A box, but it just barely fit within the load calculations. We had an unused stovetop circuit that we were able to repurpose, freeing space in the box, and gas stovetop and dryer easing the load.

Read the HPWC manual to get the basic installation requirements. You'll have to check locally about any additional requirements (a cutoff switch is sometimes required). And you need to check about your city permit requirements. You can kind of do the load calculations yourself using an online calculator (there are standard calculations and assumptions that should be used). I paid for the load calc results from one of the guys that gave me estimates. I had my commercial electrician brother in law do the work, and he knew a few things about routing conduit through boxes that the inspectors liked to see.

Lots of stuff to research. I would have been happy to pay someone else to do it all, but... brother in law...

 

[ckwong]

My main panel set up is similar to yours with a 100A sub panel for second and third floor lights and stuff. My main panel (100A) has 2 central AC/Heat, electric stove and a microwave among other smaller things and my certified Tesla electrician said I will not be able to install an 80A breaker (72A charging) but instead installed a 60A breaker (48A charging). I also had him install a NEMA 1430 as a backup in case something went wrong with the HPWC so I can still charge.

At 48A my charging rate is ~35 mi/hr, do you think you will need a much faster charging rate?

 

[gavine]

For most people, 72A charging at home is way overkill. It can come in handy on road trips perhaps, but at home? Not necessary and not worth potential electrical upgrades. Most use 50A (29MPH) and from my experience, that is plenty for home.

 

[Dirk]

I have a 2X 200A main panel and the 72A option (did not buy it but the X got delivered with it as it became standard). I had several of the Tesla recommended electricians give me a quote. The required city permit added $500 to the bill. As I live in an Eichler (people in the Bay Area will know what that is...), all wiring had to go over (and through) the roof. I had a 200A sub panel in the garage for the kitchen but that could not be used as I have a 10 kW induction range. Total bill, including the $550 Tesla wall charger, was $2500.

But that's not where my story ended. The first time I charged the car at full power, I started at 11pm as I have the EV1 PG&E rate schedule which gives me 12c/kWh between 11pm and 7am. Everything went fine for an hour but then there was a bang and all power went out. I went outside and saw that the PG&E cable to their pole was blown right off the roof! Their emergency service came out at 1 am and they capped the cable that was laying on the lawn. Next morning they came with a couple of trucks and fixed the problem. As this was outside the house, they did the work for free. They showed me the probable cause: the weight carrying aluminum neutral cable was thinned out over a couple of decades by squirrels who used it to sharpen their teeth. The thinner cable and the additional heating at that spot weakened it enough to make it break. So the whole neighborhood knew about my new electrical car.

 

[Hiquan]

Ah thanks guys! Those are some useful feedback.
Although I don't disagree with the notion that 72A at home can be overkill, I also believe to think about future proofing if I have a chance. In this case, I do not have any prior electric vehicle charger installation nor were there any consideration for it at this house at the time it was built. I have a chance now to do it and I want to make sure it can accommodate more vehicles for the future should the need arise.
Anyhow, I have a lot more information now than when I started. Thank you everyone for that.

 

[aesculus]

I'm researching on how to install an hpwc at home. I do have the 72A charge option and want to take advantage of it. My main panel is 200A and is located on one side of the house, and about 75+ feet away towards the other side is the garage. Power is split, 100A for this side of the house and the other half goes through a sub panel for remaining 100A for the AC units and dryer hookup. The garage is closest to the AC units.
In order to add this new 100A line:
Will I need to upgrade my main panel to a 400A box?

If you fill out an application with your utility (PG&E?) they can run a load calc on your service and tell you when/if you ever get close to your load max. Figure 80 amps as a rough estimate. Keep in mind of when you use your power. If you only charge after 11 pm then there is a great chance you will never accumulate enough load to overtax your panel because only the car will be consuming energy then.

Approximate cost?

Depends on how much work you are planning on doing vs an electrician and the aestics you want etc. Hard to guess $500 - $2000 maybe.

And do I need a city permit?

Yes.

Also, any idea on how to run the 100A cable to the hpwc? Dig trench around house or run some pipe to the attic and then drop down to the garage? I am approximating 75 feet for this cable run.

Depends on aesthetics and access. Cheapest and uglest is to run the cable overhead in the garage and then in conduit/behind drywall when below 8 feet. More expensive is conduit everywhere but still pretty ugly, where putting it all behind drywall is labor intensive and more money and most expensive is buried.

Good luck but I agree with others posting above. Sounds like you should definately contract the work out but you need to be informed of your options before accepting a bid.

Don't let someone oversell you on needing a new panel without first checking with your utility on when and how much load you are going to add. It's not the total number of breakers you have, but when those breakers are going to be competing for power that matters. Using the car's scheduled charging times and your utilities rates will help influence when you charge and that will make a big difference on the system you need.

 

[ShadowR55]

I had an electrician install a 100amp breaker on my main and only panel to feed two HPWC's. The main panel has a 200 amp main breaker, 3 AC units, electric stove, oven and dryer but a gas water heater. I don't have a problem with lights dimming when both cars are being charged. Most of the lights in my home are LED.

 

[boaterva]

For a lot of info, see the FAQ in my sig. Most questions should be answered there by all the cases FlasherZ has documented.

Testing overload by lights dimming isn't really the best way if anyone was actually serious.

 

[Hiquan]

Hi Lee,
Awesome FAQ thread! Not sure why I didn't search based on FAQ initially. thanks!

 

[boaterva]

Hi Lee,
Awesome FAQ thread! Not sure why I didn't search based on FAQ initially. thanks!

Glad you found it useful! It's sort of hidden in one of the other forums, which is why I like to include it in my sig.

 

[Rocky_H]

I'll just emphasize the part about that you probably don't necessarily need a 100A circuit if that is not going to fit well within your 200A service situation. First off, it's already overkill for 72A charging. 72A supplied would take a 90A breaker. Anything above that is wasted. Granted, 90A isn't a common size and might have to be ordered. 80A breaker would supply 64A, which is pretty close to your 72A level, so maybe consider that.

Also, I want to address where you mentioned future proofing. For adding more electric vehicles in the future, yes, that does make sense, because you want a big sized line, because it may have to divide into smaller pieces to feed more cars. But sometimes people have this idea that newer cars having bigger and bigger batteries or higher and higher charging power means they need to "future proof" with a really high level charging circuit, like they are buying computers that have to handle more and more bloated software in the future. This isn't like that. In fact, it's kind of the opposite. The amount of miles you drive in a day that you need to refill overnight doesn't scale up and up and up with car technology and bigger batteries in the future. And later cars might be a little more efficient, so you might get more miles on the same amount of time and power. 64A of charging current from an 80A circuit can get you about 46 miles per hour recharged. That's 276 miles even in a short 6 hour night of sleep.

 

[gavine]

That's 276 miles even in a short 6 hour night of sleep.

And, most people talk about the 8 hours of sleep time for charging, but most people are home for 14 to 15 hours a night. You CAN charge while you're awake. Some prefer overnight because of TOU rates, but again, you can charge earlier/longer if necessary.

 

[vandacca]

Having 100A Service (80A continuous charging) could mean that you you can simultaneously charge 2 vehicles at 40A each. But I agree that this is really overkill and probably only useful at most once a year for most people.

 

[gavine]

Having 100A Service (80A continuous charging) could mean that you you can simultaneously charge 2 vehicles at 40A each. But I agree that this is really overkill and probably only useful at most once a year for most people.

With my 100A dedicated service in my garage, I charge my Model X at 48A (60A breaker) and BMW i3 at 32A (40A breaker). Once the i3 gets replaced by the Model 3, I'll have to dial-back the Model X to 40A, and upgrade to a 50A breaker on the i3 circuit. The wire is already rated for 50A so no worries there.

 

[mongo]

...snip...
But that's not where my story ended. The first time I charged the car at full power, I started at 11pm as I have the EV1 PG&E rate schedule which gives me 12c/kWh between 11pm and 7am. Everything went fine for an hour but then there was a bang and all power went out. I went outside and saw that the PG&E cable to their pole was blown right off the roof! Their emergency service came out at 1 am and they capped the cable that was laying on the lawn. Next morning they came with a couple of trucks and fixed the problem. As this was outside the house, they did the work for free. They showed me the probable cause: the weight carrying aluminum neutral cable was thinned out over a couple of decades by squirrels who used it to sharpen their teeth. The thinner cable and the additional heating at that spot weakened it enough to make it break. So the whole neighborhood knew about my new electrical car.

Don't blame your poor car, the charger is 240V and doesn't add any load to the neutral conductor. (OK, if the phase conductors are right next to it, they could provide some heating, and yes the magnetic field produced by the charging amperage could have vibrated the wires, but direct resistive heating of the neutral, nah).

I hope the loss of neutral during the failure didn't wreck any of your 120V stuff.

 

[vandacca]

With my 100A dedicated service in my garage, I charge my Model X at 48A (60A breaker) and BMW i3 at 32A (40A breaker). Once the i3 gets replaced by the Model 3, I'll have to dial-back the Model X to 40A, and upgrade to a 50A breaker on the i3 circuit. The wire is already rated for 50A so no worries there.

Or get 2 of the latest HWPC and run them in master-slave mode on the same 100A line. That way the master HWPC can dynamically distribute the load based on the current state-of-charge of each vehicle.