Excellent video. I did this. I downloaded the last 13 mos electrical power usage for our home from DTE Energy here in Southeast Michigan. It gave maximum demand by the hour in an MS Excel compatible spreadsheet form. I used the "max" function and found the maximum kWh level of usage covering over 9600 hourly readings. I then divided by 240 and multiplied by 1000. The answer was 44.1 amps. So, speeding ahead, the inequality is met for the amperage levels under my consideration. Thank you!
FANTASTIC and helpful video. I've searched a long time for someone to explain how selecting a breaker works, specifically for EV. You make it very clear. I have experience adding an electrical sub-meter and am not afraid of electricity, however understanding the calculations is something I didn't want to screw around with. Thank you!
Super helpful. When putting in the new circuit, I wanted it to be capable of the highest possible draw to be as future proof as I could make it. But when selecting an EVSE you don't necessarily need one that can draw the absolute maximum the circuit can handle. I figured out that a 32 amp EVSE was going to easily handle everything I need, 99.9% of the time. So I got a slightly smaller EVSE, which does three things, all good for me: (1) it was a bit cheaper to buy initially, (2) the car charges at a marginally slower rate which is good for the batteries; and (3) the wires in the wall, the plug, etc. are all running a solid notch below what they are theoretically capable of handling, which just creates some additional margin of safety. Code is the minimum requirement you need to meet, but there is nothing wrong with pulling 32 amps through a circuit that is theoretically capable of handling 40 or 48. It is basically the same idea as plugging a 60watt lamp into a standard household outlet that can handle up to 1,800 watts. Most people who haven't lived with an EV don't understand that you plug it in when you get home in the evening and then you really don't much care how long it takes to charge as long as it is ready to go by early the next AM. Fast charging is rarely important at home, you really only care about that when you are on a longer trip and you have to top off the battery to continue the journey.
Yes, indeed. I'm trying to install an EV charging outlet in my garage. What I'm trying to figure out is: is it even worth the extra cost to buy a 240V/60A outlet and breaker as well as more copper if I will most likely charge at 24 or 32A? I might be paying an additional $100 or so for something that I will never use.
@@ledzeppelin1212 I think that depends on how long you plan to be in your current house more than anything. Batteries and charging rates are only going to get better. I decided to future proof because I may be in the house for another decade. If I knew I was moving in three years I might have done things differently. I would say you have to be confident there is a 0% chance you will need higher charging rate because plug and wire are cheap compared to the cost of the electrician. You definitely do not want to pay to have it all ripped out and replaced in five years.
Super helpful, thank you! My local utility wouldn’t let me download a years worth of data all at once, I had to do it one month at a time. I have a 200Amp panel and found that my typical monthly usage peaked around the mid 30s to low 40s in amps, but then found one day, where for about 4 hours, our usage peaked at 66Amps, which when I looked it up turned out to be a large social gathering we hosted at our house. Now I know, which is awesome! Before this I was thinking I would need to get a 14-50 outlet, but now I know my panel can support the 60Amp wall charger. Very cool!
Stick with the 14-50. My wife's 2016 model X can only charge at 40 amps anyhow, and my new model 3 only 32 amps. The 14-50 plug and cable can handle that and is cheaper than the permanent EVSE, which won't let you charge any faster anyhow. I could only fit a 30 amp breaker in my panel anyhow so I charge at 27 amps and it still charges in only a few hours. As long as it's ready by morning, who cares about charging faster, even if it is possible.
@@JethroXP Ahh, apparently all but the M3RWD are now capable of taking 48 amps, but with no option for the dual charger to get the higher capacity like there used to be.
Best of the best tutorial to figure out whether Tesla home charger can handle up to 44 mi of range added per hour at 11.5 kW / 48 amp output or not!!!! 👍👍👍👍
Thank you sir for this Master Class of this topic. Long contemplating my first EV acquisition, I now consider myself very-well informed. I do have one question remaining, regarding house electrical wiring. Working with an architect and builder, I designed and built my home 12 years ago. I requested a dedicated circuit with high-capacity wiring from the service panel to the garage wall. I told them to terminate the garage end of the wires in a standard junction box since my plan was to hard wire the wall-mounted charger. And for inside the service panel, I told them to hold off installing a circuit breaker, just leave the three wires (L1, L2, ground, NO NEUTRAL) unconnected to anything. The breaker would be selected and installed in the future. Long after moving in, I discovered that the electrical subcontractor used #8 AWG (19-stranded copper THHN/THWN-2 wires inside dedicated raceways) for the wires between the service panel and the junction box in the garage wall. It's about 35 foot run. From what I have read, based on wire gauge and the distance of the run, the highest amperage circuit breaker I can install would be a 30 amp. Agree? Or could I install a 40 amp breaker?
My breaker box was able to supply the 2 60 amp breakers I used a pair tandem slim breakers as all the slots were occupied. One tandem has the original circuits, the other handles the charger. Amperage used during charging can be controlled through the Tesla app. It is more efficient to charge at a lower current. A lot of heat is dissipated into the air at high current. When I do need to charge at a faster rate I have the option to do so.
NEC 220.82(B) and (C) has the detail how to calculate dwelling unit service load. Use 240V * rating of the panel and subtract the existing VA, that is the Max volt-ampere in remaining, take this number divide 240V or 120V depending either 2 pole or single pole breaker, now you have the Max current you can have from existing panel.
Great Video, Now i am ready to be my own Electrician :-) (Kidding) the content of this video is so clear, that now i can make sure the electrician i will hire knows his stuff
This video was great and very informative. I was wondering if you could walk through your design process for dc fast charging, how you size breakers, transformers, etc. My company is starting an eMobility division, and I’m trying to understand how the electrical side of dcfc works
Going from a 50A circuit to a 60A circuit will also require you to upsize the wiring from 6AWG to 4AWG (copper) to the EVSE, which can add significant cost to the installation.
Thank you for the detailed video. So I noticed you determined that the wire size was 4/0 and aluminum which allows a maximum power of 200 A yet your master breaker in that panel was 225 A which would require MCM 250 wire. The main breaker should be protecting the wire so I would say your panel is not correctly configured.
Thanks Ron. Regarding my panel, the main breaker size is 200A not 225A. The service wire #4/0 AL is rated for 200A (for residential applications) which matches the main breaker size 200A.
The buses are rated 225, if needed you can put a 150, 125, 0r 225a breaker to match service conductor sizes. Depending on the utility and service point definition, the utility can cheap out on the conductors upstream of the meter. That is why they are always outside, if they overheat, then they will upgrade.
This was great, My utility happens to use the same data collection as yours, so It was easy to download, mine reads in 1 hour blocks not 15 minutes, so the Kwh/Kw conversion was pretty simple,
Good advice to use data of actual energy use. The traditional "Load Calculations" are just an informed guess and will always vary from reality to some degree or other. Our Landis+Gyr meter shows max energy in kW averaged over 15 mins. With this info I see our max amperage was 78 amps, so we are well within our 200 amp service. I did a load calculation and it estimated we are at 102% of the service when in reality it's half of that.
This video was helpful, it has made me decide to never try to do this on my own. I have an electrician coming tomorrow to install my Tesla wall connector lol
Glad it was helpful. It is ok to acknowledge one doesn't have the experience and it is best to hire a professional. Safety is 100x more important than saving money.
Excellent review of how to assess your home demand for installing an EV charger. There is, however, one more piece which is not covered in this overview, which is what size wire you need to install to the charger. I purchased and installed some 8 guage romex wire thinking that it could handle 50 amps, but apparently only thhn 8 guage wire can handle 50 amps, but 8 guage romex wire is only capable of 40 amps. Thus, I presume that I can use that 8 guage romex wire with a 50 amp circuit breaker and limit the charger to 40 amps. If I knew this in advance, I would have installed 6 guage romex wire instead, but running new wire is challenging so I will start with this wire I ran and consider changing it out if I find I would want more capacity later on.
I agree. I should have covered wire size; I didn't in this video but I cover it in 2 other videos. Regarding your wire install Here's my minimum wire size design guide: (COPPER American Wire Gauge AWG) 30A circuit breaker = #10 with #10 ground 40A circuit breaker = #8 with #10 ground 50A circuit breaker = #6 with #10 ground 60A circuit breaker = #4 with #10 ground For larger feeder runs (100ft+) wires need to be upsized to compensate for voltage drop.
Good idea on checking the service wires and their max loading. But Table 310.12 may not be exactly accurate if there are high temperatures involved or different conductors are used. Ambient temperature would be considered to derate the amperage. Of course, one would assume that was done correctly in the first place with the amperage of the main breaker, but maybe it was not. If the house is old, one could see how the service feed wires were calculated to an old code standard..
And here I was thinking that you were going to explain why you would want a lower amperage over higher amperage. all makes total sense though don’t want your wires to turn into fuses
Having been Nan avid RU-vid DIY video watcher since the inception of YT, I must say that this video has been the MOST comprehensive video I have seen - a sincere and big THNAK YOU for that and keep up the great work. I have a question. As far as I gather, Tesla plug does not use the neutral wire (as your wall charger wiring indicated) - so, what is the purpose of having a aneutral wire in 14-50 plug wiring? Thnaks again!
If you are going to install a project like this, great information is contained in this video. I would say to call your building department first. They may require calculations of load based on the national electrical code ( NEC) section 220 instead of 12 months of usage data. Also, they can add, subtract, or completely ignore any or all of the building code (NEC), so the NEC may not apply to you. The NEC had a separate section with special requirements for car charging or EVSE equipment, section 625 and that section refers you back to chapters 1,2,&3 for added requirements. Can you install a charger without paying for an electrician, yes. There are a lot of requirements and rules to follow that they "mess" with every day. I encourage everyone to make sure that get the best information, the inspectors, a pro, or your own research. Just remember that a pro does this work every day and may be able to help you avoid problems you did not know you had, you might work out a deal where they give you the knowledge and you do the install. Finally,. KNOWLEDGE IS THE TREASURE YOU CAN GIVE ALL OF YOURS AWAY AND STILL HAVE WHAT YOU STARTED WITH. So, is it stealing if you get it for free by asking? And thanks for yours.
That is some really good presentation really appreciate the work that you are doing here you've earned a new subscriber can't wait for any new piece of content that you produce
Why are we dividing the kwh in our peak usage by 240? If everything in the house ran on 120, we would divide by 120, then the amperage would be higher. My house is mixed but only the stove and dryer run on 240.
While *verifying* that your service wires are the correct ampacity isn't a bad idea, if your MCB is rated *larger* than your service entrance wire, YOU ALREADY HAVE A BIGGER PROBLEM, your wiring is not nor ever was to code, and you need to hire an electrician because clearly that's not the only problem you are going to find. Note: in some situations, there may be an additional breaker between your "main" panel and the service entrance, Especially in (sane) regions that primarily locate their electrical distribution *inside* the dwelling, you can sometimes find an exterior breaker rated for the service feed, so the panel's MCB being "correct for the Bus ampacity, but too small for the incoming service" is not *technically* incorrect. Here where I am in Ontario, these types of external combination breaker / service disconnects are almost *always* associated with ancient feeds that are 60A, or (rarely) smaller if they were replacement breakers for services that were originally 30A fuse panels. They should be replaced regardless, and may be old enough to predate trip-free requirements. Meaning a jammed handle could prevent the circuit breaker from opening.
Question : Why do you devide by 240V for "Max Demand" from historic data? The US use usually 120V for normal device (which used in historic data) even though we need to add 240V device.
Great Presentation. I wish PG&E here ( San Ramon, contra costa , CA ) had provided a way to download my uses data . Without this , I won't be able to benefit from this excellent information that you shared. So I guess, I have to stay with the conventional approach of doing the load calculation based on lighting load , fixed appliances nameplate rating etc etc. You alluded to doing another video for the use-case of adding the charger to a sub panel and I have a question for this situation for now, while I wait for that video to come up. My load calculation for the whole house shows enough capacity to add 48 amp charger load on a 60 amp OCPD. But the feed from the 200 amp main panel is evenly split into garage sub panel and AC load sub panel, each protected by 100 amp OCPD at the main panel. I am told that I have to do a 2nd load calculation on the sub panel circuit with incoming service limited to 100 amp only. Is this correct ? If yes, I have less capacity to play with for sizing charger load . In my case, I am planning to add charger load to AC sub panel , which is serving two 5-ton AC units only on a 70 amp OCPD. The load calculation ( treating AC as continuous load device and taking 100% of nameplate rating for RLA of condenser / FLA of motor ) for these ACs comes to 66 amps. This leaves 34 amps extra capacity only. With this capacity, am I ok to install a 40 amp OCPD on the AC sub panel for the charger circuit and configure hardwired Tesla wall charger for 32 amp charging , following the 25% demand factor rule applied to largest motor load in the group ?
Thank you for this well done and very informative video ( frankly the best I have seen). At the beginning you mentioned that you might do another segment evaluating sub panels. I would love that. My attached garage has a 125v subpanel on a 125 breaker from the main panel ( main panel is good with 2/0 aluminum cable to the meter on a 150 amp service) with a 2awg XHHW aluminum tray cable ( thank you for discussing the direct inspection of the leads) to the sub panel . I think it is somewhat under rated , but even so I would like to know how you put sub panels in the equation. Many thanks again.
This is why I have a Span panel and EVSE. It interactively monitors what my house is using and adjusts charging accordingly. My house has 100A and my span drive is on a 60A breaker.
Great video but with an EV, you normally only need to get enough charge overnight for the next day. So while 60A/48A may be nice, I think a lower cost 40A or even 30A circuit @240V would be fine. On my Tesla MY, and just using a 120V, 20A circuit running at 12A, I get 30 miles per night and I only drive 25 miles a day.
The cost difference between a 30, 40, 50 or 60 amp circuit breaker is only several dollars. The same goes for larger wiring to support those higher amperage circuits. It's several dollars. Conduit and sheetrock work and repairs are the same. The cost of the electrician's labor is what is high. If you can find a good handyman who knows the rules in the current electrical code, that is the way to go for cost savings. Especially for most easy and simple garage interior installs.
The only reason why I went for a 50A/40A was bc I wanted the flexibility of using a NEMA 14-50 outlet vs hardwired - in the event I ever move and can unplug and move the charger myself. For the 60A/48A option, you need to have it hardwired. I hired an electrician who did a great job and charged me a reasonable $350 for the NEMA install (including mounting the Charge itself). It would’ve only cost me an additional $50 for the hardware option.
Great Video. Absolutely loved it. I just have one question, in your formula you used max demand x 1.25 and FLA to check against the service size. Shouldn’t it be (max demand+FLA)x1.25? You add all the max current demand existing+new device and then apply breaker rating to it and compare against the service breaker? (43.3+48)x1.25=114.13 < 200
I understand your logic and I personally thought the same at first; however that is not how the code reads. I quote NEC 2020: "the maximum demand at 125% plus the new load does not exceed the ampacity of the feeder." Your equation is more conservative and there is nothing wrong with that. The code allows to get away with a little more.
@@dgtv3320 Thanks for quick response and good to know that we can use a bit more than my formula :). I will subscribe to your channel for more cool videos like this. I love mathematical explanations and not too many videos cover this type of stuff in such detail.
Too complicated. If you charge your EV from midnight to 6:00 am when electricity demands is low, you’ll be fine. However, if you intent to charge your EV during the day, yes, you need to calculate and check if your electrical panel can handle such demands. My home has 100 amps max service and I only charge my EV at nigh, with no issues.
Please excuse my electrical ignorance but I do have one further question. Assuming you are using a home wall connector to charge your EV and an electrical storm passes by, would your EV be in danger of damage because of its connection to the wall connector?
Electrical guy here....yes, there is a danger. My understanding is that the wall pack contains information and relays to the car when plugged in. The actual charger is inside the car, meaning that the ac power in your house runs directly into the car before it works to charge your car. Lightning can effect your home system and travel down the wires into your car, just like the TV on your wall and cause damage. There are products out there to lessen or stop these effects. Please contact your local electrical guys with questions. Or call your local building office.
Hi Mark, yes there's a small risk damage can occur. I would make sure the charger is not plugged in to your car during a storm. I indirectly cover this topic in this video here: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-oOQTf4Lz1zY.html I also show a device that helps prevent damage.
Great Video. I have a quick question. @DG TV, Pardon my ignorance, at 8:05 minutes, why are you diving by 240 V ? In the US, the service is 110 V, shouldn't you be diving by 110 ?
Great advice but I am moving into a brand new house and have been living in a 37' trailer where my electricity is free.....the question is how do I figure this out. The new home is 1275 Sq. ft and has a 125amp service. I am thinking of putting a 40amp breaker in for my tesla charging.
Your statement is only partially true and ONLY applicable to modern homes. Homes from 1960s and older were designed and built with very different standards than today. Service wires and gear were sized very differently than today. This is why I mentioned it is CRITICAL to confirm service wire size.
I installed my Tesla charger on a 60 amp breaker but I only charge it at 20 amps which I set up in the Tesla app. I never or very rarely need to charge faster then that. I prefer to slow charge my vehicle overnight.
This is exactly what i was thinking of doing. That way you have the option on an emergency or if someone comes to visit and needs to charge while theyre there. Smart!
I sometimes charge my Tesla Y at 14amps. Don’t drive much and charge between 50-75%. See video Best practice electric vehicle (EV) charging. It has data how to get less degradation. .
The utility data is in terms of the voltage between phase A and phase B. For the majority of America that is 240v. Some new developments (apartments/condos) it can be 208v. I hope this helps.
Great video! Looking for the sub panel video you mentioned you would make. I have a detached garage with a 100 AMP service off of my main 200 AMP service. Also not sure if my power company in upstate N.Y. has the detail needed to see max usage. Thanks!
I have TXU energy and i am only able to export a year report by the day or month. Any way I can use that to make the calculations? i have a 150A breaker in my box
Great video! What would be the cost to install the wall connector by professional. My main electrical panel and garage are on the opposite end of the house :(
I see in the description you explain that you need data points every 15 minutes. My electric company can't provide that or monthly maximum demand. What I do have is a years worth of usage from every hour in KWH. Can I take that max number divided by 240 times 1000 to get max AMPs?
Im sorry but what do the service wires have to do with any of this? They’re already protected by the main breaker to prevent the wires from becoming overloaded. If anything the main breaker will trip if you have too many things on at once. But to say the service wire can become overloaded is false IF the main breaker is sized correctly.
Excellent video & very helpful - 1 question. I have 2 200 amp main panels , if I download data from electric company it would be the max load between both the panels right ? Is there a way of calculating for individual panel ?
