Amperage to home requirements- is this correct?

TheSauce

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Hi all,

Sorry To bother.

I am building an addition to my home and my contractor and his electrician are telling me with the purchase of my Taycan and wanting to install a 240V I will need to call my electric provider to tell them I will need to upgrade my panel from 200A to 400A.

Comparing to my colleagues, seems like overkill but wanted to ask around.

After my addition I will have an approximately 4700 sqft home with 3 AC units, an electric oven with gas stove top, a pool, and washer/dryer.
Do I really need 400A?
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OTPSkipper

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Probably. I have 2 ac and electric oven and stove. 200a panel was good for that with car, but Solar bumped me to a 400a panel.
 

RAHRCR

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No one could say for sure without doing an assessment of the load on your current panel. It is very likely that your electrician did so and made the recommendation accordingly. A 2nd opinion from another electrician that can visit your home would be the best way to know for sure.
 

Windpower

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The best thing is to do a load calculation. You can do this yourself or you can ask an electrical engineer to do it. When I did my last flip, I paid an electrical engineer about $300.- for a load calculation. With two AC units, LED lighting throughout the house, and a gas stove, I was only at about 120 amps. So I was able to install a 60amp circuit for the EVSE and still had room to spare.

To do a load calculation yourself, go to the 'big' appliances and see what the max draw is stated on the label on the unit. AC units can range from 15amps to 50amps, but the ones I've used in the past are 40amps. Three of these, running at the same time, would be 120 amps. Check out the electric oven.

When you add these up, there is a factor which the electrical engineer puts in, and on my last house this was 60% (60% of the total of all the appliances).

IMHO you should be able to get EV charging in a house with 3 A/C units and still be under 200 amps. But you need to run the numbers.

Last, if you are getting close to 200 amps total, you can always dial back the EVSE from 40amps (what most home owners run their EV charging at) to, lets say, 30 amps. Also I have my car programmed to charge from midnight to 6am, when you are probably not cooking dinner in your electric oven.
 


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TheSauce

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Thank you guys so much. I will do both my own load calculation and get a second opinion as well.

so basically you’re saying at 60% of my current load I should see how much amp I have left?
Ex: if 60% gets me to 100A, I have room for another 100A?
 


JustWatching

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Just like you breaker for your EV, you want to be at no more than 80% - so no more than 160amp on a 200amp.

There may be permit requirements on load (if you are planning on getting a permit as well)

Google “calculate amp load”. There are spreadsheets out there to help you figure out.

edit:
Here is one:
https://ask-the-electrician.com/residential-electrical-load-calculation.html
 
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xyeahtony

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TheSauce

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That makes sense.

Damn. That’s an annoying up-front cost to buy into the EV world. Oh well.
 

Windpower

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With 3 A/C units and a pool, youre pretty much hitting the upper limit of 200A. Technically you could install a tiny 20 amp 240V outlet and probbaly get away with it, but then you’d have to buy a third party EVSE that fits It.
I humbly disagree. I ran 2 A/C units in Los Angeles with a pool and a 60 amp circuit for the EVSE on less than 200 amps. You need to run the numbers. Its not hard, but you need to collect the data.

I just looked at the calculations I submitted to the Los Angeles building department. They take 100% of the first 10,000 watts of the total house, and then 40% of the balance plus 100% of the AC load. In my case, with the EV charger, I was at 170 amps.
 
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xyeahtony

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I humbly disagree. I ran 2 A/C units in Los Angeles with a pool and a 60 amp circuit for the EVSE on less than 200 amps. You need to run the numbers. Its not hard, but you need to collect the data.
Well i mean the OP has 3 A/Cs, not 2. Thats 40 extra amps. All 3 running together is probably 90-100Amps. Flip on the oven and that’s another 30 amps. He’s already at 120-130 on a load with those 4 things running, and that doesn’t count the pool or anything else in the house. An EV charger would run a minimum of 40 amps, putting him at 160-170amps. Thats the 80% limit for a 200A service.
 

daveo4EV

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That makes sense.

Damn. That’s an annoying up-front cost to buy into the EV world. Oh well.
in for a penny in for a pound - might as well install a 100 amp circuit for the garage - and then you're ready for future Multi-EV charging - either two separate 50 amp EVSE's or a combined shared load 100 amp dual EVSE system…

the cost of the panel upgrade will overwhelm the 100 amp circuit cost - and they you're ready for the future.

also you can hardwire a 60 amp EVSE to maximize the charge rate for your Taycan.
 

RAHRCR

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in for a penny in for a pound - might as well install a 100 amp circuit for the garage - and then you're ready for future Multi-EV charging - either two separate 50 amp EVSE's or a combined shared load 100 amp dual EVSE system…

the cost of the panel upgrade will overwhelm the 100 amp circuit cost - and they you're ready for the future.

also you can hardwire a 60 amp EVSE to maximize the charge rate for your Taycan.
This is what I did. 100AMP sub-panel in the garage. Provides a lot of flexibility/capability for future.
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