Tesla charging options

[Mayacallie]

[Topic is now in Personal Consumer Issues - mod mkc]

We currently have a 200A 30+ year old electric panel that is nearly full- 182A. We have been in the house 6 months with no electrical tripping or problems.We need a Tesla charger.
Electrician A suggests a dynamic power meter that would turn down charge rate with panel demand. This same electrician prefers upgrading to a 400 A new panel for $7450, then $1500 more for Tesla charger.
Electrician B says just tap out old panel, install conduit, junction box, new 60 amp 240 volt line with breaker to Tesla wall connector $1400. Says this is adequate if limit charging to nighttime.
If we really need a new panel for future options, then this is the time, or just band aid now and new panel if problems?

[TomatoTomahto]

A lot depends on your future plans. We have 400A service and have mostly converted our home to all electric (we do have propane for generator). My wife will probably be replacing her ICE vehicle with an EV soon, but charging only one car at a time is not a problem for us.

Overnight charging is probably the norm, unless you have solar.

I’d probably go with electrician B. Otoh, it’s really empowering (pun intended) to have 400A service.

[Ping Pong]

The sum of all your breakers is allowed to go above 200A. For one thing, the 120V breakers are only using one of the halves of the incoming 240V 200A circuit. Secondly, the breaker numbers are just telling you what their limit is. The circuits typically use less than that, and not all circuits run at the same time. Sounds like electrician A just wants money.

[MDivision]

You may want to stick to the NEC code.

[B4Xt3r]

...Sounds like electrician A just wants money.

I mean, yeah. What downside is there to installing the EV charger, and seeing if the main 200 A breaker trips frequently? If it doesn't, or even if you can work around it, you don't need a 400 A panel yet and you saved mucho coin.

Since an EV will be generally charged at the dead of night, I'd hazard a guess that it's during the hours where your electric demand of the panel is lesser than average. What do your monthly kwh usage indicate as average Amp draw? (kwh/month)*(1000 w/kw)*(month/744 hr)/(120 V). An example with 1000 kwh of monthly usage indicates an instantaneous average amp draw of just 11 amps.

Obviously electric usage is spikey, and you might trip the main breaker if you charge the EV, have an EV water heater, have an electric oven etc...

[SpaghettiLegs]

I have long (10+ years) used a 14-50 outlet to charge mine, first a Model S and now a Y. In your case I would just add a 240 line to current panel. In the unlikely case of a problem, you can always adjust charge current and timing in the car or app.

[Mayacallie]

I have long (10+ years) used a 14-50 outlet to charge mine, first a Model S and now a Y. In your case I would just add a 240 line to current panel. In the unlikely case of a problem, you can always adjust charge current and timing in the car or app.

Great to know

[MBB_Boy]

I wouldn't even buy a wall connector. Just use the mobile charging cord. Been doing that 6 years now

[Mayacallie]

I wouldn't even buy a wall connector. Just use the mobile charging cord. Been doing that 6 years now

The mobile cord is no longer free. It’s about $250 vs $450 for the wall unit

[Eno Deb]

Do you have existing 240V circuits (like a dryer outlet)? In that case the least expensive solution might be to install a switchbox that allows you to connect either the EVSE or the dryer (obviously you can't use them at the same time then).

[MBB_Boy]

I wouldn't even buy a wall connector. Just use the mobile charging cord. Been doing that 6 years now

The mobile cord is no longer free. It’s about $250 vs $450 for the wall unit

But it doesn't require the other $1000 to install in your quote

ETA: Also is mobile (obviously) and lets you trickle charge anywhere (like an Airbnb)

[Fat Tails]

Electrician B has the right solution. You are nowhere near using the full current capacity of your panel. I charge at 24 amps/240 volts and its fine. You can use the car to set the max charging current if you want to lower it.

Cheers.

[David_Cary]

Heck, I have a new house we built at "just" 200A.

We have 2 tesla chargers, 2 heat pumps, 18 kw solar, electric dryer and 3 fridges (2 are small) and a pool.

And hot water heat pump - so technically 3 heat pumps.

3800 sq ft.

Last builder did 400A every time. Slightly bigger house but used NG for backup heat. It is rare that you 'need" 400A but climate matters of course.

I charge both cars at full speed whenever without a care in the world.

[Mr. Potter]

I recently installed a Tesla charger for my daughter (yes, I’m a licensed electrician) her townhouse had a 125amp main and after doing a load calculation her electrical load was under 100amps. I wired it to full capacity 60 amp 2-pole breaker with #6 THHN conductors. During the initial programming I set the Tesla charger for 50 amps which allows my daughter to charge at no more than 40 amps after derating. Then I lowered preferred charge rate even more to 35amps on the car screen. Long story but this is should never have an issue and charges her car to 100% in 7-8 hours, perfect for overnight. As for your question ask your electrician to do a load calculation, I would bet you’re around 100 amps with plenty of capacity to add the charger, go with electrician B. Unless your home is huge, like 10,000 sq ft a 200amp service should be plenty.

[Mayacallie]

I recently installed a Tesla charger for my daughter (yes, I’m a licensed electrician) her townhouse had a 125amp main and after doing a load calculation her electrical load was under 100amps. I wired it to full capacity 60 amp 2-pole breaker with #6 THHN conductors. During the initial programming I set the Tesla charger for 50 amps which allows my daughter to charge at no more than 40 amps after derating. Then I lowered preferred charge rate even more to 35amps on the car screen. Long story but this is should never have an issue and charges her car to 100% in 7-8 hours, perfect for overnight. As for your question ask your electrician to do a load calculation, I would bet you’re around 100 amps with plenty of capacity to add the charger, go with electrician B. Unless your home is huge, like 10,000 sq ft a 200amp service should be plenty.

Thanks Mr. Potter!

[suemarkp]

Where did your 182A number come from -- a load calculation? If so, new loads go into the calculation at 40% in most cases, so a 50A charger would count as 20A. That puts you just over, so a 40A charger lets you squeak by (40A * 40% = 16A). Set the charger to 32A which will work out to a 40A continuous load. Should be fast enough for most people. Do this before the code changes, as EV chargers are causing the power companies grief. They may go into the load calculation at a higher number (maybe 60% or 100% instead of 40%) in the future.

There are alternative methods to calculate your panel load. If your power company has average power usage over 15 minutes intervals for the last year, you can use the highest 15 minute value they recorded (most power meters have this capability, but the utility may not record it for residential customers). Need to know if it is KW or KW-Hr. If KW-Hr, multiply by 4. KW, you use as is. Take the kilowatts, divide by .240, and that is your max amp demand which you can use instead of 182A. But how you expand after that is some different rules -- it is more than just the 40% figure from above.

[Tyler Aspect]

Easy decision is option B. Just dial down car charging rate to half of maximum and your breaker will never trip. It does not matter if your car changes at night for 2 hours or 4 hours.

[TheGreyingDuke]

In my region, Upstate NY, a 400 amp service exposes you to demand charges whereby your monthly rate is determined by the peak usage for the period, best to avoid.