How many of you have 100A home service and charge on a 30A circuit?

[pdp1]

I have 100A electrical service at my home. We also have an electric cooktop, electric oven, electric dryer, and central A/C (heater furnace is gas BTW). Using some online load calculators, adding a 30A charging circuit would push me to the hairy edge of enough total current for my home. Just for the record, I'm pretty sure the A/C compressor/condenser is on a separate main breaker than the 100A main service, but not 100% certain.

That said, I've read that many Tesla owners only charge at night where almost nothing high powered is being used in the home, so the extra 30A from the EV charger is no big deal... and some have even gone with a 50A charger in the same scenario as me. I'm also confident that I will rarely charge the car and simultaneously use other high powered appliances so, personally, I'm not concerned about tripping any breakers. It would be extremely easy and cost effective for me to add a 30A breaker in the subpanel in the garage to charge my car and I would highly prefer this route rather than upgrade my home to 200A service.

My question is, I live in California, would I be violating any safety or code regulations by doing this?

 

[woodisgood]

Similar situation as you. I added a 30A circuit and we charge on this with no issues. We need about 120 miles of charge per night for the daily commute. The 30A is not limiting for us at all - takes about 4.5h to charge from ~40% to 80%, and slower is technically better for the battery anyways.

In most electrical panels, the total sum of the individual breakers will exceed the service size, and this is considered just fine if some consideration is made to what those circuits are and which ones are likely to be used simultaneously. As with any code-related question, you should consult with a local electrician or your code department for the final say, but you're probably going to be just fine with an additional circuit that is intended to be used when the rest of the house is mostly "quiet."

 

[djgarrett21]

I'm on 100 amp service and have a fairly large/power hungry home. I did the load calc too and determined I was fine to install a 60 amp circuit. I've got a HPWC installed which pulls 48 amps and have never encountered a problem.

 

[BrokerDon]

We installed our Tesla High Power Wall Charger ("HPWC") 3+ years ago on a 100A breaker in a 100A subpanel on a 200A / 240V main service panel with the HPWC dip switches set to the 80A maximum load. I pulled our electrical permit using the Load Calc our electrician completed and everything was installed per electrical code by a Tesla approved licensed electrician... and inspected and signed off by the electrical inspector. It's worked great. No issues charging our 2015 MS P85D's 85kW battery. Never tripped a breaker or had load issues with our other appliances because we charge overnight between 10:00M and 8:00 AM on SCE's TOU-D-B "Super Off Peak Rate".

FYI we always charge our 2015 MS P85D at 60A instead of the maximum 80A charge rate since charging at the higher 80A rate definitely heats up the HPWC cable & plug as well as our P85D's charge port. Definitely better for long term reliability of these components to charge at the lower / cooler 60A charge rate... which can still easily recharge our P85D's completely empty 85kW battery overnight in ~ 6 hours.

 

[compu85]

We're on ~100 amp service*, but have gas heat and cooking. Only the dryer is electric. We have a 40A charger on a 60A breaker, 26A on a 30A, and a 15A on a 30A breaker shared with the dryer. What doesn't help is that out transformer is shared with 7 other houses on our street, so even if we upgraded our service I don't think the transformer could handle it.

*Our panel is rated for 200a. But there is no main breaker, so I don't know what our technical max service is.

-J

 

[pdp1]

Similar situation as you. I added a 30A circuit and we charge on this with no issues. We need about 120 miles of charge per night for the daily commute. The 30A is not limiting for us at all - takes about 4.5h to charge from ~40% to 80%, and slower is technically better for the battery anyways.

In most electrical panels, the total sum of the individual breakers will exceed the service size, and this is considered just fine if some consideration is made to what those circuits are and which ones are likely to be used simultaneously. As with any code-related question, you should consult with a local electrician or your code department for the final say, but you're probably going to be just fine with an additional circuit that is intended to be used when the rest of the house is mostly "quiet."

I'm on 100 amp service and have a fairly large/power hungry home. I did the load calc too and determined I was fine to install a 60 amp circuit. I've got a HPWC installed which pulls 48 amps and have never encountered a problem.

It sounds like I should be fine then... Did both of you have the load calc done by an electrician or did you do it by yourself like I did?

I'm confident I can do the work myself because the location where I'd mount the 14-30 receptacle is only about 1 ft away from the subpanel box so the run will be a piece of cake. But before I start, I wanted to make sure I'm not violating codes by not getting an electrician to sign off on the load calculations I did.

 

[djgarrett21]

It sounds like I should be fine then... Did both of you have the load calc done by an electrician or did you do it by yourself like I did?

I'm confident I can do the work myself because the location where I'd mount the 14-30 receptacle is only about 1 ft away from the subpanel box so the run will be a piece of cake. But before I start, I wanted to make sure I'm not violating codes by not getting an electrician to sign off on the load calculations I did.

I did the load calc and branch circuit myself. I'd strongly advise you spend time getting up to speed on your local code. If required, get a building permit and get it inspected. Do it all above board and you'll be fine. A 1ft run from a sub panel sounds about as simple as it gets, but still worth doing the homework.

 

[pdp1]

I did the load calc and branch circuit myself. I'd strongly advise you spend time getting up to speed on your local code. If required, get a building permit and get it inspected. Do it all above board and you'll be fine. A 1ft run from a sub panel sounds about as simple as it gets, but still worth doing the homework.

Thanks! I think I know what I need to do now before I start work. I'd give your post a like but it doesn't look like I can do it yet!

 

[davewill]

You really should nail down where that AC circuit breaker is located, apart from this effort. You should be able to apply for the permit and get signed off on the load calc part of it before you do the work. If the city will accept it, you should be good to go.

 

[pdp1]

You really should nail down where that AC circuit breaker is located, apart from this effort. You should be able to apply for the permit and get signed off on the load calc part of it before you do the work. If the city will accept it, you should be good to go.

I have 2 breakers in my main service panel, a 90A and 50A. The 90A circuit for sure goes to the subpanel in my garage. The subpanel in the garage feeds everything in my house except for the central A/C... I do not see a breaker for the A/C in the subpanel. Therefore, my conclusion is that the 50A breaker in the main panel goes to the A/C. Side note, the A/C compressor has a fuse box right next to it as well. I hope my logic here is correct!

 

[davewill]

I have 2 breakers in my main service panel, a 90A and 50A. The 90A circuit for sure goes to the subpanel in my garage. The subpanel in the garage feeds everything in my house except for the central A/C... I do not see a breaker for the A/C in the subpanel. Therefore, my conclusion is that the 50A breaker in the main panel goes to the A/C. Side note, the A/C compressor has a fuse box right next to it as well. I hope my logic here is correct!

Makes perfect sense. You could turn off the breaker and verify there's no power to the AC is you wanted to be absolutely sure. The disconnect at the AC compressor is a requirement so that service personnel can be sure the power is off while they're working.

 

[adaptabl]

Get a permit and ask the inspector before you do anything.

 

[EdM3]

The problem with these exercises in the abstract is that adding doing a survey of your appliances and adding up loads ends up not being reflective of what your actual usage looks like, since the highest current devices are usually not running all at once. Your power company may provide an online hour by hour kWh report for you that with a little work, will give you a very rough approximation of your amperage consumption. Apart from charging, you should see peak usage when your washer/dryer is running and when your AC or heating is running. You'll need to guesstimate whether the loads are 120V or 240V to get an amperage but it's ballparkable. If you want something precise, ask your electrician to run a load test that involves them installing a logger for about a week to see peak usage. If you're in a condo, your HOA may want to see that for both your unit and the overall building service before it's subdivided into individual units since some buildings have concerns with their overall service capacity. You may find that you're not using as much power as you think - my actual usage is turning out to be a fraction of what the online load calculators would estimate and a lot of the hand-wringing around EV capacity turned out to be for nothing.

 

[pdp1]

The problem with these exercises in the abstract is that adding doing a survey of your appliances and adding up loads ends up not being reflective of what your actual usage looks like, since the highest current devices are usually not running all at once. Your power company may provide an online hour by hour kWh report for you that with a little work, will give you a very rough approximation of your amperage consumption. Apart from charging, you should see peak usage when your washer/dryer is running and when your AC or heating is running. You'll need to guesstimate whether the loads are 120V or 240V to get an amperage but it's ballparkable. If you want something precise, ask your electrician to run a load test that involves them installing a logger for about a week to see peak usage. If you're in a condo, your HOA may want to see that for both your unit and the overall building service before it's subdivided into individual units since some buildings have concerns with their overall service capacity. You may find that you're not using as much power as you think - my actual usage is turning out to be a fraction of what the online load calculators would estimate and a lot of the hand-wringing around EV capacity turned out to be for nothing.

This is exactly how I feel, I have very little doubt that when I finally take delivery of my car and start charging on a regular basis that I will even come close to tripping any breakers. However, I just wanted to make sure I'm not painting myself into a corner from the point of view of regulations as I've never added a whole new circuit to my subpanel before; I've only ever added outlets to existing circuits inside my home. I was tempted to just tap into my dryer circuit since the dryer plug is literally on the other side of the wall of where I want to have the new outlet in my garage, but figured it would be much safer to add a new breaker just in case one of these nights the dryer is still running at 1am for whatever reason while the car starts charging.

 

[MorrisonHiker]

This is exactly how I feel, I have very little doubt that when I finally take delivery of my car and start charging on a regular basis that I will even come close to tripping any breakers. However, I just wanted to make sure I'm not painting myself into a corner from the point of view of regulations as I've never added a whole new circuit to my subpanel before; I've only ever added outlets to existing circuits inside my home. I was tempted to just tap into my dryer circuit since the dryer plug is literally on the other side of the wall of where I want to have the new outlet in my garage, but figured it would be much safer to add a new breaker just in case one of these nights the dryer is still running at 1am for whatever reason while the car starts charging.

You might also consider the Dryer Buddy™

 

[compu85]

You might also consider the Dryer Buddy™

That's how we share our dryer plug with a 15a EVSE (which works fine for the ELR since it only has a 3.3kw charger...)

 

[Rocky_H]

NEC has a provision for load calculations for non-coincident loads, which means circuits which will generally not be used at the same time. So if you have a daytime load and a nighttime load, you can pair those up and instead of having to count both of them added together, and you can count only whichever is larger.

So with the given load you already have, which passes code already, you should be able to add a charging circuit that is offset from your clothes dryer or oven, and no bigger than that, and it would not increase the calculated load.

 

[tga]

I have 100A electrical service at my home. We also have an electric cooktop, electric oven, electric dryer, and central A/C (heater furnace is gas BTW).

Before upgrading my service to 200A, I had the same setup, minus the central A/C. I charged at night at 24A for almost 2 years before the service upgrade. My nighttime load without charging is a couple of amps. I set the car to charge at 11pm. Occasionally the car would start before a load of laundry finished, but I was still well under the limits of the 100A service

We're on ~100 amp service*, but have gas heat and cooking. Only the dryer is electric. We have a 40A charger on a 60A breaker, 26A on a 30A, and a 15A on a 30A breaker shared with the dryer. What doesn't help is that out transformer is shared with 7 other houses on our street, so even if we upgraded our service I don't think the transformer could handle it.

*Our panel is rated for 200a. But there is no main breaker, so I don't know what our technical max service is.

-J

You definitely have a main breaker somewhere, you just haven't found it. Maybe at the meter? You can't leave the main service feeders unprotected. I have a single 200A breaker at the meter, with a "main lug" 200A panel. "Main lug panel" = no main breaker in the panel (think a sub panel with the breaker upstream), vs "Main breaker panel" = panel with a main breaker.

 

[pdp1]

Before upgrading my service to 200A, I had the same setup, minus the central A/C. I charged at night at 24A for almost 2 years before the service upgrade. My nighttime load without charging is a couple of amps. I set the car to charge at 11pm. Occasionally the car would start before a load of laundry finished, but I was still well under the limits of the 100A service

Our A/C is on a completely separate circuit than the main 100A service so in that sense, my situation is exactly like yours. Thanks for letting me know you didn't have problems, another similar data point never hurts when it comes to making me more confident.

 

[Jedi2155]

100A is 24 kW. Its rare for most homes to be drawing that much power.

I have a 5 Ton HVAC (50A, 6 kW), Electric Range (40A), 32A EVSE (40A), and 12x20A branch circuits. Never had an issue. I do not have a pool though. I'd be a little more concerned if I was doing a Model S 60A+ charging, or 48A, is a bit on the edge. 32A is pretty safe IMO.

I could see an issue if you're running the AC, charging, all 4 burners on the Electric range AND electric oven. But if only 2 were running and the rest of your house had moderate usage you're probably fine.

If it really does become a problem, I would then consider getting a 200A upgrade. I'd also consider 200A upgrade if you're thinking about a 2nd EV down the line for simultaneous charging.