OWNERS - What house electrical panel size is required for 240V 50A charger to be installed? (see body for details)

OWNERS - What house electrical panel size is required for 240V 50A charger to be installed? (see body for details)

This is assuming there is a microwave, electric oven, electric dryer, electric washer, electric water heater, electric fridge, and electric A/C also on the panel.

Most of the properties i have looked at have a 150A panel, and all of the above.

So my question is basically inquiring what panel size would be required to have all of the above, plus a 50A 2-pole circuit for an EV charger. My goal is to have the panel upgraded (if needed), and have the breaker installed so that if AND MORE IMPORTANTLY WHEN i get my Tesla, i will only have to install the circuit and receptacle in the garage.

What are your experiences?

BigJack | 21. Januar 2019

IANAE, but I understand that this is done by load factor: add up the amperages of all the breakers in the existing panel, multiply by some factor which you will have to look up on the Internet, and compare the difference to your service.

andy.connor.e | 21. Januar 2019


Thanks. The factor multiplier is by 0.8 for continuous loads, which would be applicable to everything but general receptacle circuits. Household receptacles are not typically rated for continuous load, so i shall do that thanks.

sheldon.mike1010 | 21. Januar 2019

Had similar to above items plus hot water spa on a 100 amp panel.
Three electricians bid an EV addition in the garage just behind the panel.
all 3 said go to 200 amp. Literally pennies difference in breaker that determines amps
going from 150 to 200.

mrburke | 21. Januar 2019

I have a 240V 100A panel at my 100+ year old house. I was able to install a 50A circuit for a wall adapter.

If you are going to upgrade you panel, you may want think about a second meter just for EV charging. It may get you a better rate depending on where you live and who you power company is.

eplaskett | 21. Januar 2019

Only an electrician who does a true load calculation could tell you for certain. It's going to depend on how large the house is, which in turn impacts how many outlets and light fixtures you might have on at any one time. House size is also going to be directly correlated to the size of the AC system, which is going to be a large portion of total current draw.

If you want to do a rough estimate, there are some load calculators available online, such as this one:

As far as my own experience is concerned: we have a 3,150 SF house, spread over three levels, plus a 1200 SF unfinished basement. We have two AC systems (one for the top two floors, and a second, smaller one for the main floor). Our water heater and cooktop are gas, and the oven and dryer are electric. Heat is from gas, with electric forced air handlers. We have two full-sized refrigerators - one in the kitchen and one in the basement garage. We have 200A service with a 200A panel, and when the Tesla-certified electrician did a load calculation prior to our wall connector installation, he found that we had plenty of capacity to support the wall connector on a 60A breaker (48A continuous draw when it's in use). It works great!

andy.connor.e | 21. Januar 2019

Will anticipate a 200A panel will be needed. Thanks for the info

Lonestar10_1999 | 21. Januar 2019

@andy - keep in mind that if the original panel has a 150A panel (main circuit breaker) then it may be sized for the electric utility service cable ampacity.

If you desire to upgrade the panel to 200A, it pays to ask the utility if a service entry cable upgrade would be required.

andy.connor.e | 21. Januar 2019


Thanks for the tip. I assume that the service upgrade would be required with the panel upgrade. Wire size changes are significantly different for 100, 150 and 200. Would not make sense for the service to oversize a feeder to that extent.

Iwantmy3 | 21. Januar 2019

Just taking the opposite perspective here. I have all the same things on my circuit that you do (other than the electric water heater). Yet, I now have a 50 amp 240V line supplying my HPWC all on my 100 amp wall panel. Yes, if you go through all of the load factor calculations they will tell you that you need more. However, I only charge my car between midnight and 6 am. I am not running my dryer, oven, microwave etc. during those hours. At that time, only the A/C and a few minor appliances are operating. It just means that if I ever want to charge during the day, I will need to be aware of what is running. I have not had to think about it yet.

My guess is that you are going to charge over night as well.

slingshot18 | 21. Januar 2019

My specs:

4400sqft house, 2 floors
2 AC + air handlers over 4 zones
3 refrigerators
2 microwaves
LED yard lights, front and back
3 TV's, Xbox, computers, printers, etc..
lights are all LED
furnace, stove, oven, water heater and dryer are gas
60amp HPWC
2 solar systems

200amp breaker (as built) handles it all fine.

kevin_rf | 22. Januar 2019

@mburke, Did the second meter route. You needed to make sure the savings on the EV plan will offset the extra meter cost and taxes you now have to pay twice. It worked out for me, about $20-$30 less a month, but I also drive 30k a year and have a very generous TOU plan.

If the OP can not fit a 50amp breaker, smaller breakers for 15amp, 20amp, 30amp could be used with the correct NEMA plugs and adapters from Tesla. The down side is the longer charge times.

billtphotoman | 22. Januar 2019

We have 100 amp service in our townhome and changing that would require trenching. Fortunately our dryer is gas so I was able to repurpose the dryer circuit to install a 32 amp Juicebox. I picked the Juicebox because it allows me to software limit the maximum current which I do during air conditioning season to avoid the risk of potentially pushing our 100 amp total limit if we are running some high draw appliances while the AC and car charger are running. Even if I limit the Juicebox to 20 amps it still adds plenty of range per hour.

TM3Q | 22. Januar 2019

In Québec old houses had 100A panels, now new houses have 200A panel. It all depends how much load you already have but have in mind the Tesla charger use give or take 11,5 kW wich is more than 1/10 of a 100A.

wiboater4 | 22. Januar 2019

I'm getting away with using a 100 AMP panel like Iwantmy3 is. Pretty much the same situation . I charge overnight when not using much, I am 100% electric in my house , have an on demand water heater and Geothermal furnace. So far no problems but I am probably going to upgrade to a 200 AMP panel this summer because I want to go to a higher capacity on demand water heater anyway. I do have the Tesla wall connector set at 48 amps.

SalisburySam | 22. Januar 2019

Load balancing is a good way to keep total loads low enough for constrained power, i.e., make sure you do not run the charging station, dryer(s), summer HVAC systems, ovens and other high draw items simultaneously to ensure panel, wiring, or breakers are overloaded. The better but expensive solution is to add sufficient power, wiring, and circuits to meet the total need, whether used or not. At some point, that power will likely be used if not by you then by whomever buys your home in the future.

Upgrading power to the home can be expensive, but to me, usually worth it, especially for re-sale. Yes, you can operate on 100amp service with some care in how you use your loads. Some things to consider if you do upgrade, which I highly recommend if you can afford it for several reasons and peace of mind:

1- utility company may have to replace their transformer to higher capacity (their expense)
2- utility company/electrician may have to replace wires into the service panel from transformer (probably your expense)
3- may need new meter
4- will likely need new service panel/breaker box (your expense) to get more circuits and breaker spaces, and beefed up innards to accommodate new bonds and grounds if needed.
5- will likely need new circuit breakers if the load center is different brand
6- will likely need new arc fault breakers for required circuits, similarly for ground fault breakers
7- will need to meet national and local electrical codes, permitting, and inspections for such an upgrade
8- electrician should be licensed locally and practicing in your area

We moved into a 1906 home that had an entertaining mix of wiring “styles” and a broken ground among other deadly issues. We buried and upgraded the wiring from the transformer inward. We had 150amp service before, now have 400amp on two 200amp load centers. We should be good for a while, and our circuit flexibility has increased. Our kitchen service is an example: we can run two coffee makers, a microwave, dishwashers, disposers, fridges, wine chiller, ovens, and so on in our kitchen as it has a wild number of dedicated 120v and 240v circuits. Don’t have to think about not using something else when I pull out the toaster or waffle maker...just plug in and use. Also, my homeowners’ insurance company was very pleased when we replaced old wiring and it reflected in the cost for replacement value and fire risk insurance when they appraised the home.

brisket1 | 22. Januar 2019

We have a 100A panel too, in our ~50 year old house. It helps that our heating, water boiler, dryer, range are all gas. We have a 50A breaker for the Nema 14-50 outlet with no issues so far. Never had it in the summer when the electric AC is running with a 40A breaker for it, so I guess I'd have to be more careful then.

terminator9 | 22. Januar 2019

I have 200A but honestly a 150A would have been fine. If I add up all the breakers on my panel, they would obviously add up to more than 200A. For example there is a 20A going to cooktop. I have a gas cooktop so the only electricity it needs is the ignitor which is probably less than 1A. the 15A breaker for lights don't really draw 15A. And you don't constantly run dryer, washer, oven, car charging that draws the most amp.

andy.connor.e | 22. Januar 2019

Thanks everyone! The goal would be to have a setup in which i dont have to worry about what is being used. I can see myself on a hot summer weekend cooling my house and trying to do laundry, and realizing i forgot to charge my car during the week, and now im stuck in a predicament where i have to choose which appliance to not use.

That being said, if its going to cost literally thousands and thousands of dollars to upgrade the panel (and perhaps the service), then i'll make it work. I will know better than to run everything at the same time. I have control over all of my appliances, and i completely agree with the notion of "Just limit charging to night time", which is probably exactly what i will do. But we all know there are times when you have your head up your a$$, or perhaps work keeps you extra late.

Appreciate all the info, this at least gives me an idea of what to look at while checking out properties, and what i could expect moving forward!

kevin_rf | 22. Januar 2019

@TM3Q Your math is suspect at best kW is amps x voltage

120v outlet (12a x 120v) = 1.4 kW
Mobile Charger (32a x 240v) = 7.6 kW
Wall Connector (48a x240v) = 11.5 kW

100a panel (100a x 240v) = 24 kW
150a panel (150a x 240v) = 36 kW
200a panel (200a x 240v) = 48 kW

So TM3Q, 11.5kW is 1/3 of the capacity of the OP's panel.

Like I said, if the panel is the limiting factor other charging options at lower speeds are available with the correct NEMA connector and Tesla adapter

NEMA 6-15 240v with a 15a breaker will charge at 11 miles per hour. This is the most straight forward conversion where you install a slim 15a double pole breaker in the box and run the same wire you run 120v 15a with. It most likely does not need you to do a load calculation, but the charging rate sucks with a capital S.

NEMA 6-20 240v with a 20a breaker will charge at 15 miles an hour. This also probably won't break the panel, if you have to run a new wire, do this over a NEMA 6-15.

NEMA 14-30 240v with a 30a breaker will charge at 22 miles an hour. A little more beefy on the load, but has a decent charge rate. It will draw 24 amps on your service. Less likely to break the panel then higher current options.

It is worth noting that the Tesla Mobil Connector draws a max of 32a using a NEMA 14-50. A NEMA 14-50 can actually source up to 40a continuous. 40a is what an electrician will use in the load calculation.

ArcticStation | 22. Januar 2019

@andy.connor.e “Will anticipate a 200A panel will be needed.”
Yes! When I bought my then new house thirty years ago, the realtor made a big deal about the 200 amp service, the fact that every circuit in the house was twenty amps or greater and that there was lots of room in the panel to support additional circuits later on. I didn’t think much about it until that panel started to fill up with two air source heat pumps, a heat pump water heater, a kitchen upgrade that included two wall ovens and a separate cook top, a welder in the garage and now a NEMA 14-50. My builder’s foresight IRT the electrical service has saved me a LOT of aggravation and money during the upgrades. Sadly, my daughter and son-in-law, who plan to buy a Tesla soon, just bought a newly built spec house with 150 amp service, 15 amp circuits to most outlets and a full panel! We’re already talking about sub-panels, dryer buddies and other workarounds that could have been avoided if their builder hadn’t taken an “as long as it meets code, it’s good enough” attitude. And my daughter is already complaining that she can’t run multiple kitchen appliances without tripping a (15 amp) circuit breaker, something that has never happened in my house with its 20 amp circuits. Go for a place with a 200 amp panel.

andy.connor.e | 22. Januar 2019

I'll have to run a circuit to the garage no matter what. No other way to get 240V there unless it already exists for whatever strange unforeseen reason. I dont think i'll need a bulky breaker (50A), 30A should be plenty.

kevin_rf | 23. Januar 2019

Go the NEMA 14-40 route then.

kevin_rf | 23. Januar 2019

Fat fingers, NEMA 14-30

andy.connor.e | 05. März 2019

Just had an inspection done. House has 150A panel, and luckily the water heater is not electric. I was told a 30A or even 50A circuit would be no problem to accommodate, no need to upgrade the panel.

Will also be looking into the solar roof since i found out it needs to be replaced in the next 2 years.

Carl Thompson | 05. März 2019


If you recently bought a house then congrats.

If you're going to have solar installed at some point then you'll probably need to upgrade so I'd go ahead and upgrade the panel (and the connection itself) now while you're having work done. I have a small house but needed to upgrade to 200A when I got solar.

Also, if you've come into a large windfall then maybe solar tiles make sense. But Tesla (and other companies) offer much better value solar packages for the not-as-wealthy.

gwolnik | 05. März 2019

Be sure to allow capacity for an electrically heated hot tub, 240V is more efficient. That will also require a subpanel near the spa.

srenfrew | 05. März 2019

I have a 200A panel. I have all electric also (dryer, oven, water heater, etc). When i had a load test done before my NEMA 14-50 install, with everything on (ac, over, dryer, hot water, microwave, tvs) i was pulling around 120a. I have the 3 set to charge at 10:30 pm each night, when everyone is pretty much close to sleeping.

jer1776 | 05. März 2019

Go 50A if you have the capacity vs 30A as it will be more efficient to charge the car. I have a 50A, which I get about 30 miles per hour charge and is only pulling 32A as the car has a setting to not draw the max amps. I also suspect the mobile connector also has built in safety to ensure it does not run hot so not pulling at it's max capacity.

Outlets like NEMA 14-50 are not designed to have plugs constantly removed like common household outlet. So if you plan on going on trips with the car, just buy another adapter for $35 and leave the one at home always plugged in.

ODWms | 06. März 2019

@jgeek, do you know where I can get another adapter for $35? I leave mine plugged in in the garage, but I’d like to have another if they’re that cheap.

wiboater4 | 06. März 2019

ODWms , I think he's talking about only the end adapter not the whole mobile charging kit. I'd suggest getting a different adapter not already in the kit and installing a plug for it. That way you'd also have an extra adapter like say a welder plug for example.

derotam | 06. März 2019

@jgreek, just to clarify what you said. The car will not pull more than 80% of what it thinks the circuit is. The adapter dongles for the mobile adapter tell the mobile connector/car what the max draw can be. The mobile connector will only do up to 32A max no matter what.

andy.connor.e | 13. März 2019

Thanks for all the suggestions. According to Teslas solar roof estimator page, the solar roof would cost less than my car finance cost. Im thinking maybe i will pay off my car by next year, and replace that monthly payment with the solar roof. Not sure yet.