House Breaker Box Maxed Out

[Uncle Paul]

My Tesla approved plug installer did a load check, and installation was approved by Tesla for my application.

He went complete through my house, noting every appliance's draw, including airconditioning units. Sent this load calculation to both his company's engineering and Tesla before starting the job.

Replaced the breakers with upgraded units that took up 1/2 the space of the older style, so did not need to add another panel (saving costs)

He relabled the box to identify the Tesla stuff and made everything look easy.

 

[MXWing]

Best:
Upgrade to 200A service
Get two Tesla Wall Connectors. Chain them together with 100AMP Breaker
Max Draw: 72 AMP.

Cost Efficient:
Stay at 150A Service
Get one Tesla Wall Connector now and charge at 48AMP on a 60AMP Breaker.
Add Tesla Wall Connector and chain off Wall Connector and share 48AMP.

There is also costing differences to go between 48 AMP and 72 AMP chargers on the vehicles as well.

 

[3Victoria]

Also, consider if your electricity supplier has a different rate for EVs, if so then a second meter might be required to take advantage of it.

 

[MXWing]

Also, existing breakers can be group into combo breakers which frees up space in the panel.

Anything like a panel upgrade will be $$$ so go all in on doing it right for future expansion or doing it cheap with the solution suggested above.

Electrician may sell you more than what you actually need.

 

[brucet999]

I'll have to have the electrician look the panel over on Monday to see if we can free up something. I could make do with a 50A circuit for now. Plus to be honest, we carpool in her SUV about 50% of the time anyway. Our work schedule is far from static....

Call the power company today and find out how big of a panel their service cables can support at your house. That info will help your electrician.

 

[BerTX]

Another factor -- some brands of older breaker boxes are unsafe and need to be replaced anyway.

 

[Rocky_H]

When charging starts the two chargers will use max current, but as the cars "fill up" they use less power, so both cars can be charging at "full speed" after a few hours.

I don’t want to just leave this sitting out here in this thread uncorrected, but it’s another detail to learn.

You have a concept that is somewhat right, but it doesn’t apply here for home charging, so I don’t want it to mislead people accidentally.

You are talking about the battery tapering and slowing down the charge rate as it gets full. You see that at Superchargers, where a nearly empty battery may be at 115kW or so. After a while, you see it slow down to 80, 70, 60, etc. That is still several times higher than the home charging level of 10kW on a 240V 50A circuit. You won’t see home charging slow until about 98-99%, so it’s always going to be at full rate all the way to people’s daily charging limit. So in the case of this sharing system, both cars will want the whole 40A if they have any charging to do, and will still have to divide it and take less than they would like.

 

[JHuberman]

Hmmm... That's interesting. On a bad day driving separately, we should be commuting a combined total of 180 miles. At 40A - 30miles/hour charging rate, it should only take between 6-8 hours of charging total.

Keep in mind that for the first few hours both cars will be sharing the 50 amps, but as they fill up and the battery acceptance goes down then the 50 amps will be enough for the cars to both be charging at their full amount.

 

[Rocky_H]

Keep in mind that for the first few hours both cars will be sharing the 50 amps, but as they fill up and the battery acceptance goes down then the 50 amps will be enough for the cars to both be charging at their full amount.

I just explained above how that's not true. Well, at some point, one of the cars will hit the charge limit you have it set for and just stop charging, so then the other car can get all it wants, but that's different.

 

[MorrisonHiker]

Best:
Upgrade to 200A service
Get two Tesla Wall Connectors. Chain them together with 100AMP Breaker
Max Draw: 72 AMP.

Cost Efficient:
Stay at 150A Service
Get one Tesla Wall Connector now and charge at 48AMP on a 60AMP Breaker.
Add Tesla Wall Connector and chain off Wall Connector and share 48AMP.

There is also costing differences to go between 48 AMP and 72 AMP chargers on the vehicles as well.

Actually, the max draw could be 80 amps if an older S with dual chargers is connected. The 72 amps would be correct for newer vehicles.

 

[Altes]

On Saturday, my wife is going to test drive a Model X. This will be for her car and not mine as I already have a reservation in for the Model 3. This will be our first time ever in a Tesla actually. Depending on how it goes, we might be placing an order for one. Though, who am I kidding... I don't really see her not liking it.

One of the steps that I was planning on doing down the line for the Model 3 was to get 100 amps to the garage for charging. I feel this will suffice for 2 EV's with the HPWC power sharing feature.

Our house has a 150A breakerbox and it is completely maxed out. My question is how an electrician will get 100A to the garage? Will the main breakerbox have to be upgraded to 250A-300A (in order to install a 100A breaker for the garage) or can the original 150A breakerbox be kept and a second 100A breakerbox be installed in the garage? I'm just curious if I "HAVE" to route the power through the main breakerbox due to some code or something. I know this can vary from state-to-state (I'm in VA).

You'll need a load calc to see how close you are to your 150A service limit (local code here is 70% load to limit). Since you have no more spots for breakers in your current box the cheapest route is a sub panel from your current box, NEC requires a single cutoff to ALL electrical circuits at one location

I am going thru the same thing, Likely going to need to upgrade service to at least 150A even though i have gas everything and ALL LED lighting in the house, I wish the NEC would catch up with technology. IF you do upgrade service have them pull the largest cable possible from the pole/demarc so as to future proof.

 

[MXWing]

You'll need a load calc to see how close you are to your 150A service limit (local code here is 70% load to limit). Since you have no more spots for breakers in your current box the cheapest route is a sub panel from your current box, NEC requires a single cutoff to ALL electrical circuits at one location

I am going thru the same thing, Likely going to need to upgrade service to at least 150A even though i have gas everything and ALL LED lighting in the house, I wish the NEC would catch up with technology. IF you do upgrade service have them pull the largest cable possible from the pole/demarc so as to future proof.

You can replace existing breakers with combination breakers. A sub panel is -not- required in all cases.

AC is not gas, that will hurt the load calc the most.

 

[iwannam3]

A "combination breaker" is a normal dimension breaker that is 2 breakers in the space of a single breaker. If the panel is full and has sufficient amp rating you can use 2 "combination breakers" to free up space for a 240 breaker.

 

[TexLaw]

I must admit that a lot of this is over my head, but there is one thing that I do know about electrical service: if you are upgrading, getting more than you need isn't always as bad a deal as you think. I've been very thankful a couple of times that I had excess capacity.

 

[Ardie]

I don't know about the rest of you folks, but I foresee a fairly hefty increase in electrical power consumption, and I want to plan ahead for it.

Today, we have houses with 80-100 amp circuit breaker panels, and that's designed for homes without an electric car.
Tomorrow, fossil fuel will be scarce. We may replace our gas furnace, gas water heater, gas clothes dryer and gas oven over to all-electric. This in addition to the two electric cars in the garage. So I'm thinking that 200 Amps will seem wimpy.

If electric cars continue on their march toward "More Power!" I expect that their charging rates will eventually get in line behind Tesla and offer charging capabilities of 200-500 miles of range per hour. Maybe not 5 years from now, but quite possibly in 10 years.
So a requirement for a circuit breaker panel to be able to handle 300 Amps is not crazy talk.

But is *is* crazy talk to expect our Edison company to *supply* that kind of juice to me sometime next year. I just want to have the capability to handle it on the day when we have a couple of electric cars that can soak up 500 miles of range within an hour -- each.

So I don't have to populate that box with all kinds of circuitry right away; I just need to plan that it will probably happen someday.

-- Ardie
Maybe a 300 Amp breaker panel, plus the solar panel interface, plus the PowerWall interface. I hope I don't burn the house down.

 

[Rocky_H]

Today, we have houses with 80-100 amp circuit breaker panels, and that's designed for homes without an electric car.
Tomorrow, fossil fuel will be scarce. We may replace our gas furnace, gas water heater, gas clothes dryer and gas oven over to all-electric. This in addition to the two electric cars in the garage. So I'm thinking that 200 Amps will seem wimpy.

But this is neglecting the other part of technological advancement--low power. Old tube TVs were power hogs. Flat screens are much lower power. Incandescent bulbs consumed much more energy than CFL or LED bulbs. Energy efficient furnaces, air conditioners, water heaters, refrigerators, etc. etc. So it has seemingly been an ongoing balance as we get a bit more electronics, with computers, laptops, tablets, phones, etc. that need to use electricity, all of the appliances use a bit less energy each decade as well.

If electric cars continue on their march toward "More Power!" I expect that their charging rates will eventually get in line behind Tesla and offer charging capabilities of 200-500 miles of range per hour. Maybe not 5 years from now, but quite possibly in 10 years.
So a requirement for a circuit breaker panel to be able to handle 300 Amps is not crazy talk.

Now this is the part that doesn't make sense. You drive X number of miles per day for work and errands. If cars have 300 miles of range or 500 or 800, you still drive that same X number of miles each day. If the cars can refill at 29 miles per hour, or 200 miles per hour or 500 miles per hour, that still doesn't affect that you drive X number of miles each day that you need to refill at night, which means that is still the same number of kwh you need to put into the car overnight, which means that you don't need to keep increasing your home electrical supply higher and higher for faster and faster charging.

 

[Baja30]

I wasn't aware the Tesla charges could talk to each other, how do you set that up?

If you can't get the charges to talk to each other (to share a 50 amp circuit), then you could just wire both chargers to the same 50 amp circuit and set up the cars to charge at different times. I typically only need 4 hours or less to charge my car. One car could start at 9 pm, the other start at 2 or 3 am. Only challenge here is if one car is still charging when the other turns on, you will pop the breaker.

 

[BrokerDon]

My Tesla approved plug installer did a load check, and installation was approved by Tesla for my application.

He went complete through my house, noting every appliance's draw, including air conditioning units. Sent this load calculation to both his company's engineering and Tesla before starting the job.

Replaced the breakers with upgraded units that took up 1/2 the space of the older style, so did not need to add another panel (saving costs)

He re-labeled the box to identify the Tesla stuff and made everything look easy.

The Tesla recommended electrician we used did the same thing:

• recouped an 30A / 240V clothes dryer circuit since we have a gas dryer
• replaced the older breakers with upgraded units that took up 1/2 the space freeing up spaces for new breakers
• did a complete Load Calc on our existing breakers & panel which I attached to our electrical permit application
• put our 1st generation Tesla High Power Wall Charger on a 100A breaker enabling us to charge at 80@ / 240V... but we RARELY charge at this high rate since it heats up the Tesla HPWC cable, plug and socket on our Tesla. Instead we charge at 60A / 240V which keeps the Tesla HPWC cooler which is MUCH better for electronics while still recharging at 40 ~ 41 MPH... more than enough to recharge our P85D overnight even if it was at ZERO miles remaining in less than 6 hours.

 

[Altes]

You can replace existing breakers with combination breakers. A sub panel is -not- required in all cases.

AC is not gas, that will hurt the load calc the most.

What's AC?? (I live in San Francisco!!!)

 

[Ardie]

But this is neglecting the other part of technological advancement--low power. Old tube TVs were power hogs. Flat screens are much lower power. Incandescent bulbs consumed much more energy than CFL or LED bulbs. Energy efficient furnaces, air conditioners, water heaters, refrigerators, etc. etc. So it has seemingly been an ongoing balance as we get a bit more electronics, with computers, laptops, tablets, phones, etc. that need to use electricity, all of the appliances use a bit less energy each decade as well.

Now this is the part that doesn't make sense. You drive X number of miles per day for work and errands. If cars have 300 miles of range or 500 or 800, you still drive that same X number of miles each day. If the cars can refill at 29 miles per hour, or 200 miles per hour or 500 miles per hour, that still doesn't affect that you drive X number of miles each day that you need to refill at night, which means that is still the same number of kwh you need to put into the car overnight, which means that you don't need to keep increasing your home electrical supply higher and higher for faster and faster charging.

Rocky_H,

Quite true, the amount of power required for a car will (probably) remain in the 3-4 kWh/mile range for now. But the battery capacity will increase from today's puny 20-50 kWh to something more like 500-1,000 kWh. And its going to be a challenge to refill it overnight using a J1772 240V/50A line. Even more challenging if you have two cars.

And whenever did we like waiting for more than 5 minutes at a drive-thru window for fast food? the future "we" will want them to recharge in minutes, not hours.

Also, there are a jillion homes out there with natural gas appliances, and if natural gas becomes scarce, then people will switch to electric appliances. (Nah! Gas will be cheap forever!)

I'm not all that sure that the march of efficiency will keep pace with the march of ... More stuff. True, the march of efficiency has supplied us with electronic goodies use less power than the old ones, but let's face it: we have more electrical goodies now. Four TVs instead of one. Electric garage door openers, can openers, heated towel bars, coffeemakers, toaster ovens, hair dryers, heated towel bars, security cameras, robot vacuum cleaners, wireless stuff galore. Its not the efficiency has not made my electric bill go down. It is all the additional goodies (and goodies yet to be made) will cause consumption to go up.

So, I will still plan on a big circuit breaker box to handle whatever comes.
And if I'm wrong, then I will have squandered a couple of hundred bucks for a larger, but partially empty, box.
And if I'm right, then I will be thought a visionary to have planned so far ahead -- when I sell the house because I'm moving to Mars.

-- Ardie
Muskville? Elonopolis? Teslaburg? Spacex City?