Previously we covered wireless charging, ultra-rapid charging, and long range EVs in our look into the future of mobility. Today we tackle one of the biggest current topics in electric vehicles, vehicle-to-grid (V2G) technology.

For the uninitiated, vehicle-to-grid or V2G technology allows electric vehicles to dump power back into the grid, lessening overall strain and lowering your monthly power costs. It's a great idea in theory, afterall, if electric vehicles are sold in the tens of millions each year that is going to put a big additional strain on the power grid and some think it will spike electrical costs right when rates are already the most expensive. EVs are literally batteries on wheels and by using their extra capacity to power your home during peak hours you could save quite the burden on the grid and a little extra cash as well. While all of this sounds great, like most things EV there is a lot of misinformation, so let's dive in.

Achieving the Impossible?

V2G is such a new idea that it wasn't even tested until recently, so for much of the debate no one had any real data on the subject and some thought the idea was potentially impossible. In fact, most "studies" around the idea of feeding power from vehicles back into the grid are still in the beginning stages. While most agree that this technology is, in fact, hypothetically possible, it seems we have a long way to go before we have the raw facts.

Just how long will it be?

Well currently BMW and Pacific Gas and Electric are testing V2G technology, however, in the first 18-month roll-out of the pilot, they only tested a demand response feature of the vehicles (which isn't V2G). In short when PG&E noticed a spike in demand they sent a signal to slow or completely stop charging. While this is certainly an interesting study its also a bit unnecessary as technologies like SmartPower remove the need for demand response by using power more efficiently and ensuring drivers get a full charge the next day. The big question isn't whether it'll work or not (it looks as though it will) its whether we should do it in the first place and a new study indicates its not a great deal for everyone.

Good For Them, Bad For You

Assuming that feeding power from your car back into your home or the larger grid is possible (again it probably is) means the power companies are going to have a much easier time ensuring the peak demand doesn't cripple the overall grid. While that is great news for them and to a smaller degree you, it's not such a good thing for your car.

A study by the University of Hawaii found that discharging your vehicle's battery then recharging it significantly decreases its performance. Finding that by doing this on a regular basis could limit the usable lifetime of the battery to a mere 5 years or ~50,000 miles. While its still not fully known how long a given battery pack will last, tests on the Tesla Roadster (the oldest available long-range model) indicate that it can last anywhere between 97,000-366,000 miles depending on how often the owner tops up and how they do it. For those driving the vehicle down to 0% and then charging up at a DC fast station each time, may see the battery life tumble. However, if you have charging at home or work and make sure to plug in regularly the battery could easily last 350K (on par with a typical gas-motor).

The bottom line is that batteries like to stay full and by having the dump out all their power then recharge again will have a severe negative effect. So while this technology is great for the power company, you are ensuring your car will need a full battery replacement in short order.

The Other Solution

Right now battery technology is still evolving but it appears that V2G does a lot of harm to your car's battery, and when more than 50% of the entire cost of the vehicle is the battery that's not a great solution. However, there is an idea that's readily available that does essentially the same thing, Tesla's Powerwall.

The idea here is to fill the Powerwall's battery up during the middle of the day when electrical rates are the lowest and then use that power later on when the peak rates apply. By doing this, owners could conceivably tie the Powerwall to a solar panel and then charge their vehicle at night, essentially providing them 100% free power to handle all their driving needs. In fact, because most drivers only go ~40mi/day owners could use this power in many other ways, although they should be careful as the Powerwall is the same as a Tesla and will wear down quicker the more is charged and discharged over a period of time.

V2G is an interesting concept and most likely will become a reality at some point, but until we are able to make batteries that can withstand the high amount of punishment they will take it's simply not a feasible idea today.