New 3 car detached garage: how big should the wire be

[John K Jordan]

… The power company here considers a separate meter for an outbuilding to be a commercial account and the extra charges for the privilege get put on the bill. …

Same here.

[John K Jordan]

…

one thing I did ask the builder for is a 2” pipe from house to garage with a pull cord so we can add other kinds of wire in the future. Optical fiber, maybe. Who knows?

Suggestions?

When I built my shop (250’ from the meter) I dig a 24” wide trench and ran 3 consults. Two are 2”, one with the electrical conductors (#1 copper) and the second empty except for a rope. I added a 1” conduit on the other side of the trench with 2 cat6e ethernet cables, one for data and the second a spare, just in case.

I know nothing about EVs but calculate wire size according to the voltage drop tables based on the worst case of power use. I don’t see underground wiring runs as a place to try to save money. The cost of even big copper wire is insignificant relative to the total cost of the construction. I may never push the capacity but what about the next owner?

JKJ

[Jim Becker]

It occurs to me that there may be no good reason not to wire for 200 amp service to that building as the living quarters upstairs may even trigger that requirement in some jurisdictions. That will easily cover two EV chargers running simultaneously as well as the LQ including HVAC. As John noted, there's just no good reason to economize on what goes in the ground...

[Alan Lightstone]

My biggest problem with EVs is charging time. But that's while traveling. For home charging speed isn't that important most of the time. For a 3 car set up I would do one dedicated level 2 charger and a second power sharing (also called dual charging) level 2 charger. That'll be two 50 amp circuits, not 3. So the question is how often do you plan on driving 200 miles a day in all 3 cars in multiple days in a row? Most likely never.

A very good point. I don't know of any owners of three EVs right now, so never heard what any individuals do. I'll hopefully have a second EV next year or 2024 (whenever Tesla finally starts shipping Cybertrucks and my reservation number comes up), so I'll have to figure out a way to juggle 2EVs charging. But I would suggest the OP wire the house to be able to charge all 3 EVs at once. Frankly, having the space for all 3 EVs to charge at once (you would have to have 3 locations that fit your EVs with outlets close to them) to make this work. Not easy in many houses. Wouldn't work in mine, but with his new construction with a 3 car garage (you did spec out the wider garage door so that it really can fit two cars, right? I know many people who were burned by "two car garages" which really don't fit two cars side by side in the double door.)

The smart charger is an interesting idea, but I would save the money and just put three NEMA 14-50 outlets in three locations.

[Alan Lightstone]

It's better that that. Just like with gasoline, you don't (often) run it all the way down before you recharge. I'd expect that most people would recharge when they get down to about half charge. So if you had a 90kWh battery, you'd need to put about 45kWhs into it. At 40 amps and 240 volts, that's a bit less than 5 hours. If your electricity was $0.30/kWh, it would cost you about $13.50 to "fill the tank". That's quite a bit less than for gasoline.

Mike

Actually, talking with fellow EV owners, there is tremendous variation as to how people charge them. But I don't live in California, so time-of-day charges aren't in effect here.

I know owners who plug in their car every night. I know ones who charge when it's about half empty. I know ones who take the car down to about 20% capacity.

Personally, I tend to charge the car before the weekend, and usually do it in daytime with the solar panels running full. No real reason for that, it's just what I do.

With a Tesla, you are told not to charge the car more than 90%, or let it get down to 10% to maximize battery life.

In my case, I have a Tesla charger and charge at 48 amps. Usually takes about 4-6 hours to fully charge, depending on where we started. What I tell people is that as long as your car can be fully charged by morning, it's irrelevant how long that takes. So arranging for 80 amp charging with a Tesla charger is a silly waste of money. As it would be for other EVs assuming some can charge using that much current in the future. Most won't.

[Roger Feeley]

Many fires from EV's!
I wouldn't even consider such an undertaking. Nothing against EV's.

Bruce

Ive heard about the fires too. I found an article
https://www.autoweek.com/news/a38225...bout-ev-fires/


A better way of looking at electric vehicle fires is to compare the number of fires per 100,000 vehicles sold. Researchers from insurance deal site Auto Insurance EZ compiled sales and accident data from the Bureau of Transportation Statistics and the National Transportation Safety Board. The site found that hybrid vehicles had the most fires per 100,000 sales at 3474.5. There were 1529.9 fires per 100k for gas vehicles and just 25.1 fires per 100k sales for electric vehicles.
The reason why it's easy to think that electric car fires are so common is because EVs are still novel and still unknown to a large portion of the public. News and media outlets report on electric car fires more often because of its, which can make it seem like they are a common occurrence. What's more, when there are highway vehicle fires, they can require a tremendous amount of effort from emergency personnel to extinguish the blaze. A chain reaction inside the batteries—sometimes called thermal runaway—can occur when the battery generates more heat than it can dissipate.

[Mike Henderson]

Ive heard about the fires too. I found an article
https://www.autoweek.com/news/a38225...bout-ev-fires/


A better way of looking at electric vehicle fires is to compare the number of fires per 100,000 vehicles sold. Researchers from insurance deal site Auto Insurance EZ compiled sales and accident data from the Bureau of Transportation Statistics and the National Transportation Safety Board. The site found that hybrid vehicles had the most fires per 100,000 sales at 3474.5. There were 1529.9 fires per 100k for gas vehicles and just 25.1 fires per 100k sales for electric vehicles.
The reason why it's easy to think that electric car fires are so common is because EVs are still novel and still unknown to a large portion of the public. News and media outlets report on electric car fires more often because of its, which can make it seem like they are a common occurrence. What's more, when there are highway vehicle fires, they can require a tremendous amount of effort from emergency personnel to extinguish the blaze. A chain reaction inside the batteries—sometimes called thermal runaway—can occur when the battery generates more heat than it can dissipate.

I question the number of fires in hybrids - that would indicate that 3.5% of all hybrids sold catch fire each year. That's a LOT. If that many were catching fire, there would be a lot of action to address the problem.

MIke

[Lee Schierer]

Ive heard about the fires too. I found an article
https://www.autoweek.com/news/a38225...bout-ev-fires/


A better way of looking at electric vehicle fires is to compare the number of fires per 100,000 vehicles sold. Researchers from insurance deal site Auto Insurance EZ compiled sales and accident data from the Bureau of Transportation Statistics and the National Transportation Safety Board. The site found that hybrid vehicles had the most fires per 100,000 sales at 3474.5. There were 1529.9 fires per 100k for gas vehicles and just 25.1 fires per 100k sales for electric vehicles.
The reason why it's easy to think that electric car fires are so common is because EVs are still novel and still unknown to a large portion of the public. News and media outlets report on electric car fires more often because of its, which can make it seem like they are a common occurrence. What's more, when there are highway vehicle fires, they can require a tremendous amount of effort from emergency personnel to extinguish the blaze. A chain reaction inside the batteries—sometimes called thermal runaway—can occur when the battery generates more heat than it can dissipate.

Many fires from EV's!
I wouldn't even consider such an undertaking. Nothing against EV's.

Bruce

Be careful where the data comes from. Car and Driver has an article that says the NTSB and NHTSA don't collect car fire data. The National Fire Incident Reporting System (NFIRS) doesn't break their data down by vehicle type. It would appear that AutoInsuranceEZ may have data no one else does.

[Bill Dufour]

Co worker has a small rental house in the backyard. They installed a separate meter, fed from the main house. They bought their own meter and read it themselves. They charge the tenant based on their readings. The power company is not involved beyond the main house meter.
I believe it is minimum $25/month to have metered service plus charges for any power used. With more solar installations that minimum will be going up. I have read an extra $60 per month for solar. I have no idea how much an extra meter on one service drop would be.
Bill D

[Adam Herman]

distance and load are critical. sounds like you should hire an electrician. Car chargers can generally be set to different max charge levels, just did a ford lightning charger last week and we set it to 48 amps to use existing wiring and save the guy a bunch of money. You can overthink this stuff way too much with "what if".
pick a panel size, size the wire for that main breaker and distance keeping the voltage drop in spec.

I am studying for my journeyman.

with 3% voltage drop at 240 volts and 100 feet distance I get #1 CU or 3/0 alum.

for 300 feet i get 350kcmil alum or 4/0 CU

k=12 for CU
k=20 for AL

[Roger Feeley]

all,
Great advice. I won’t be doing this. I just want to be an informed consumer. We have a 400 amp service into the main house. There is a 120amp breaker supplying our “granny flat”. I’m thinking another 100 amps or so to the garage.

I should mention here that the living quarters electrical needs will be minimal. No stove. Just a mini-fridge, toaster oven and induction countertop hob. There will be a mini split type heat pump and a very modest HW heater. It’s really more of a guest quarters.

I agree with the consensus that charging three electric vehicles from nothing at the same time would be rare. If the tech doesn’t already exist, I would imagine that some means of juggling multi-car charging will come along.

[Kev Williams]

--from a March 2, 2022 article in Forbes:

he fire risk from electric cars appears to be less than for conventional vehicles, although Americans awaiting their new Volkswagens to be delivered from Europe could be forgiven for doubting that as their new cars were destroyed, apparently by a spontaneous lithium-ion battery fire on the Felicity Ace car transporter ship.

The ship sank Tuesday.

evshipsinks.jpg

Any firm conclusions on fire risks generally are not yet possible because there is not enough data to decide that pure electric cars are more prone to spontaneous fire than internal combustion engine (ICE) ones, or more likely to burst into flames after an accident.

As for the fire on VW’s car transporter from Germany to the U.S. carrying almost 4,000 vehicles, probably including battery-electric Porsche Taycans, Audi e-Trons and VW ID.4s, a report in Britain’s Daily Mail quoted the Felicity Ace’s captain Joao Mendes Cabecas saying lithium-ion batteries in the electric cars on board caught fire.

...Recent data whipped up a storm on both sides of the argument. Electric car enthusiasts liked the idea that National Transportation Safety Board (NSTB) data, analysed by AutoinsuranceEZ, showed BEVs were far safer than hybrids and ICE cars. AutoinsuranceEZ said the numbers showed electric cars were less prone to fire than other vehicles, with hybrids the most dangerous, followed by gasoline vehicles.

Hang on a minute said the doubters, the data shows no such thing. Graham Conway, principal engineer at the Southwest Research Institute in San Antonio, Texas, said there’s not enough information to decide if EVs are more prone to spontaneous fire than ICE ones.

“It is still too early to make any conclusions about EVs and spontaneity of fires. I just don’t think we have the sample size of data or the reporting structure for fires to say with any certainty. What is clear is that the fire is more difficult to deal with, the energy release during the exotherm of the electrolyte takes a lot of cooling to extinguish,” Conway said

Conway said the data didn’t allow for solid conclusions.

“The NTSB data said that after 41 fatal collisions involving BEVs, 1 caught on fire (2.44%). The NTSB data said that after 20,315 fatal collisions involving gasoline vehicles, 644 caught on fire (3.17%). The NTSB data said that after 543 fatal collisions involving gasoline hybrid vehicles, 12 caught on fire (2.21%),” Conway said.

“But 41 crashes vs 20,315 crashes vs 543 crashes make it statistically irresponsible to compare these numbers. For example, if there was a 42nd crash with an EV and it caught on fire then it would be 4.76% of EVs or double the rate of hybrids. Until the sample size is the same and significant we just can’t say which will be worse or not,” Conway said.

MY 'sketchiness' towards EV's are the number of spontaneous fires that seem to occur. Aside from its battery being the cause, I've never once heard of a gas vehicle just simply catching on fire. I have no desire for an EV, but should I ever get one, it will never be parked in a garage that's connected to the house...

[Alan Lightstone]

Co worker has a small rental house in the backyard. They installed a separate meter, fed from the main house. They bought their own meter and read it themselves. They charge the tenant based on their readings. The power company is not involved beyond the main house meter.
I believe it is minimum $25/month to have metered service plus charges for any power used. With more solar that minimum will be going up. I have read an extra $60 per month for solar. I have no idea how much an extra meter on one service drop would be.
Bill D

Duke Energy just started charging $30.00 plus tax down here as a minimum charge. Even if you use less (we have a surplus with solar panels). I'd imagine they'll keep trying to raise that in the future. That's just with one meter. Not sure how much they would add for a second meter. Not sure if you have Duke Energy in Virginia.

[Mike Henderson]

Duke Energy just started charging $30.00 plus tax down here as a minimum charge. Even if you use less (we have a surplus with solar panels). I'd imagine they'll keep trying to raise that in the future. That's just with one meter. Not sure how much they would add for a second meter. Not sure if you have Duke Energy in Virginia.

Here in CA, they started charging a "grid charge" to support the cost of maintaining the grid. That's fair because anyone who has solar depends on the grid and should pay a fair price for that.

I'm grandfathered in for a few years because I put solar in very early - so I don't know exactly what the monthly charge is. The grandfather is limited in time so I'll find out eventually,

Mike

[Ole Anderson]

Many fires from EV's!
I wouldn't even consider such an undertaking. Nothing against EV's.

Bruce

Boy, that is a contradictory statement.