[dragontamer]

I understand that my estimates are a bit off, but you're welcome to provide a back-of-the-napkin power-capacity result yourself if you think you have a better methodology.

5000-homes x 7kW charger == 35MW of capacity that needs to be added to my neighborhood. Still a lot of electricity, no matter how you cut it (upgrading from 20MW current capacity -> 55MW).

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As I said, I don't have hard numbers. But we need a starting point that we agree upon for planning purposes. If you have better numbers, please share.

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> Tesla Model 3 has a range of 250 miles at 54kWh. Say you need a range of 50 miles every day. 50mi/250mi range * 54kWh = 10.8kWh per day. This can easily be charged overnight at ~3.5kW (220V * 16A) - will take a little over 3 hours.

EDIT: https://www.fueleconomy.gov/feg/noframes/41189.shtml

26 kWh/100 miles. EPA measures 13kW-hrs of charging every 50-miles. So my numbers are slightly different, but still within the magnitude of your result.

But that mileage will be different in the winter. This link suggests a drop of 33% efficiency... so 50-miles needs 20 kw-hrs of charging. https://teslamotorsclub.com/tmc/threads/33-range-loss-in-col...

[iknowstuff]

For America: The average commute is 16 miles. 16x2/250x54kWh = 6.912kWh/day. Most modern residential circuits are 15 or 20 amps, so we're looking at a max load of either (15A x 120V =) 1800W or (20A x 120V =) 2400W. 6.912kWh/1.8kW = 4 hours of charging.

5000 * 1.8kW = 9MW when all cars are pulling the maximum load. Mind you, they will be pulling it at night, when there is excess capacity available due to lower energy use from other appliances.

[dragontamer]

> The average commute is 16 miles.

That's 32-miles from home-to-work-and-back, not including grocery shopping or kids activities, or leisure activities (ball-games, bar, restaurants).

I think 50-miles is closer to reality. The average car is driving far, far, more than 16-miles per day in my experience.

32-miles just from work alone.

> max load of either (15A x 120V =) 1800W or (20A x 120V =) 2400W.

No sane person will be charging on 120V x 15A. Your 77kW-hr Tesla 3 will take 42-hours to charge on that circuit. 20A x 120V is going to take 32-hours to charge from empty. Similarly ridiculous.

Well, almost. I actually am a big proponent of hybrid-vehicles. A hybrid vehicle with 50-mile capacity will charge on a 120V x 15A circuit every night just fine (and use gasoline as a range-extender when necessary). Until power-infrastructure is better built out, I think the PHEV model is going to be friendlier to our cities and neighborhoods.

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To put it another way: 120V x 15A circuits charge your car at 7-miles (of range) per hour (of charging). For small batteries such as PHEVs (Volt, Prius Prime), this might be sufficient (20-miles of electric charge, maybe 50). For a 220+ mile Tesla 3 (or any other high-range electric vehicle), that's too slow.

[iknowstuff]

I agree you'd want a better circuit. In Europe, people will simply use three-phase outlets to get 12kW. We are talking about average power consumption overnight though. About whether huge infrastructure changes are immediately necessary/insurmountable, or if we'll get by just fine. Trickle charging to replenish the energy used on an average day clearly does not need a lot of power. Even 50 miles can be recharged in 5 hours overnight.

[dragontamer]

Sometime in the next 10 years, we'll have "smart grid" systems which will coordinate high-load activities such as car charging, appliance usage, air conditioners and more.

"Smart grid" doesn't exist yet however. For now, people will plug in their vehicles... maybe synchronized after 8pm (or whenever "night-time" energy kicks in, to save a bit of $$$), and charge at 7kW from their 3-phase power unit for the next 2 or 3 hours.

The energy companies will see this as a big spike at 8pm when the car-charger timers automatically go off, and then the energy usage will let off by 12-midnight or so.

[davidgould]

What you keep seeming to miss is that you only charge the amount you drive. If you drive 50 miles you can charge on a level 1 (120V 12A = 1.4kW) in 8 hours while you sleep. It does not matter whether the car is a Spark EV (18kWh battery) or a Tesla P100 (100kWh battery) because you only charge to replace the amount you used up, not the total amount the car could hold.

[dragontamer]

If you have a Tesla Model 3, and drive 100-miles in a day (ex: go to work, visit your cousins for their birthday, then come home), it will take 14-hours on a regular 120V x 15A charger to recharge those 100-miles.

8-hours of charging on 120V x 15A charger only charges 55 miles. You won't "recover" the 100-miles until 20-days later (-100-miles from a big-driving day, +55 miles of charge on Day1. -50 miles on the 2nd day, +55 miles on Day2, etc. etc).

Realistically speaking, the 120V x 15A charger is simply insufficient for people who actually drive 50-miles a day (and occasionally drives 100-miles).

Factor in the 33% loss of energy in the winter, factor in a mistake or two (ex: forgetting to plug in the vehicle), factor in a few nights without power (ex: hurricane or California Fires), and you're completely sunk.

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If you're buying electric, you need the 7kW charger (or faster), to ensure that your vehicle is fully topped off every night. That way, on your "emergency" days when two or three things happen (hurricane + visiting the cousins), you'll have enough charge to actually make it through the day.

Alternatively, buy a PHEV so that you can always leverage gasoline in those high-milage or power-outage situations.