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Comment by manmal | Hacker News Reader

Most newly built electric cars have a 50+ kWh battery. Imagine if smart meters could use _that_, regardless of where the car is currently parked and plugged in. 50kWh is in excess of what most households use in electricity on most days.

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That many cars seem undesirable in urban areas (or anywhere, really, but let's not go there).

From a bit of quick searching, EV battery packs are roughly the same volume as a fridge, and weigh in around 300kg (that was a Nissan Leaf specifically, but I assume others are similar). I don't have enough room for a fridge sized battery in my house. It'd be nice if they could shrink a bit. With enough capacity to run a tankless water heater for the duration of a nice, hot shower. The battery can charge slowly whenever power is abundant.

The grid doesn't care about running a bunch of laptops. But a bunch of tankless water heaters quickly add up. Having a local buffer really makes sense there.

On the other hand, if every home had a load leveling battery system of even modest storage capacity, say, 15 minutes average power usage covered, then load leveling would not be nearly the problem it is today.

You're probably right. Something like a small battery per home, and a bigger battery per block would likely go a very long way in creating a more stable grid. That's probably cheaper than "real" grid scale storage. What would a 15 minute battery look like? Probably not much bigger than a car battery. Install one with every power meter. Sounds so easy that I can't help but wonder what the catch is. Why aren't we doing this?

> Imagine if smart meters could use _that_, regardless of where the car is currently parked and plugged in.

The US National Electric Code (NEC) has been updated (§625) so that electric vehicle charging can be used as a source of power (PDF):

* http://mydocs.epri.com/docs/publicmeetingmaterials/1112/PDNN...

This will be the case in the next couple of years. Wall boxes are inherently smart (that is, controllable). So as a sink, the concept works somewhat already. But most cars won't be empty all the time. Also as source the 50kWh will only be usable as an emergency backup for the owner of the vehicle and only if they have the infrastructure to consume directed current. No one will let their own battery drain for the greater good. For public use cases people won't offer to unload more than maybe half of the capacity, realistically maybe 25% on average.

> No one will let their own battery drain for the greater good

Agreed. That’s why you‘ll get adequately paid for the energy sucked out of the battery in the evening when everybody starts cooking and energy prices on the market spike.

The big problem we have right now is that we want to get rid of coal and gas, but they are currently absolutely necessary for serving peaks occurring when wind power and solar lie flat. Vehicle2grid could be the solution - a giant distributed battery. I think if you charge 40kWh in the day with cheap solar, and sell it for 5x the price in the evening or morning, that would more than offset the battery degradation (which is way less of a problem than initially suspected, especially when charging and discharging slowly). A big battery could make you a couple of bucks every day.

Yes and add to that the ability of many of these large-battery vehicles to self-drive. For example when the owner is working during the day, the vehicle could drive to a regional charging station. This could help with the distribution component e.g. in rural areas with no power lines for the last few miles — the vehicle simply drives the power from where it’s available to where it’s needed.

50kWh can cover about two to three weeks for me. Unless you use electricity for heating, you don't really need all that much.

That’s impressive.

We don’t use electricity for heating (heating and warm water are powered by community heat), and need 11kWh per day on average, excluding the EV. The EV adds another 5.5kWh per day.

My main consumers are probably the fridge and the oven. I made sure to buy an efficient fridge. Other than those I usually only have a laptop or two running. The washing machine only runs once or twice a week, most of the time only at 30°C.

Well we are four people in the household. I guess that does increase consumption.

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