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Comment by nine_k | Hacker News Reader

This assumes that if you have driven 160 miles, it will take 40 hours to get the full charge. It does not look like a good selling point for home charging.

To feel at ease, an electric car owner should have a fast charger at home or very nearby. A Tesla supercharger is 72 kW, which is 2-3 times more a detached house can normally receive from the grid.

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On average, it's like 800W. My current home charger and cars support up to 7.7 kW. It's something like 4 hours to go from near empty to full for one, and about twice that for the other one (very different sized batteries). But what that really means is that the charger will click on for a relatively short time, then sit idle for the rest of the day. It's likely that most home chargers won't exceed 40A for a while, as past that needs hard wiring. Though I suspect V2H capable chargers will all be hard wired.

The point is things average out over even hundreds of homes. A single home might be charging at 7.7kW all night long after a long trip to refill a 100kWh battery. However, everyone in the country doesn’t suddenly show up with an empty battery every Friday and then need to fully charge that night.

Which means even if people are installing 5+kW charging stations it’s little different than when everyone started installing AC.

The grid is also built on the assumption that maybe one in five ovens are likely to be turned on at the same time, that doesn’t mean each oven can only be used at one fifth power.

You assume that a car needs to be fully charged each morning. If you for whatever reason drive 160 miles each day, but may only recuperate about 40 miles (in rough worst case of say ten hours at a home Level 1 [standard US electrical outlet] charge over night), you still need only need a "full charge" on a 300 mile battery every two days or so.

The economics shift even more the closer you get to the mean daily commute of 32 miles roundtrip. For instance if you travel 45 miles daily and only charge 40 each night you'd need nearly two full weeks before your range dipped below 200 miles. At that rate you'd need a full charge maybe once every month and a half (assuming of course that you have no other sources of topping up your miles in a month in a half, such as convenience chargers while shopping or work sponsored chargers during the work day).

In the Netherlands the average car drives 32 kilometres per day. You can easily charge that much at home.

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