What is Bi-Directional Charging and Why Do You Need it?

by Guest Blogger, Craig Cole, Senior Editor, EV Pulse

If you’ve never owned an electric vehicle, there are a lot of confusing terms, like kilowatt-hour… plug-in hybrid… heat pump… and CHAdeMO.

Another one that a lot of drivers don’t understand – or even know about – is something called bi-directional charging, but it’s a feature you’re going to want. In simple terms, bi-directional charging allows your electric vehicle to feed power back into your home, or beyond.

How Does Bi-Directional Charging Work?

Normally, energy comes from your house and goes into your EV – when you’re charging the battery – BUT with bi-directional charging, in certain situations, electricity can come out of the vehicle and go back into your house. The power can flow both ways, hence the name bi-directional. But why would you ever want this? Well, it is an amazing feature for several reasons.

The single biggest benefit is that bi-directional charging allows your EV to function like a generator. Say there’s a power outage. Depending on usage, your electric vehicle could provide enough juice to run your entire household for days.

It’s easy to forget just how much energy is stored in EV batteries. Take the F-150 Lighting, for instance. With the extended-range pack, Ford says this all-electric truck can power your house for three days, or 10 if you ration carefully – that’s more than a week! This makes bi-directional charging a game-changing technology.

Also, you never need to worry about having a separate generator, whether there’s enough gas in the tank, or if it will start when you need it. And of course, with bi-directional charging, crisscrossing extension cords through your house to make sure the fridge and freezer stay plugged in is a thing of the past.

Now, I know about whole-house generators, they’re super nice and they streamline this entire process. HOWEVER, they run on fossil fuels, which are not clean, AND you have to buy them separately, which is another expense, and not a cheap one. If you own an EV that supports bi-directional charging, you could save thousands of dollars by NOT having to purchase, maintain, and fuel a separate generator.

Bi-Directional Could also be Vehicle-to-Grid (V2G)

Similarly, bi-directional charging may also allow your EV to feed electricity into the broader power grid even if there isn’t an outage. You may have heard this referred to as vehicle-to-grid, or V2G.

Sometimes, it’s hard for utilities to keep up with demand – like if it’s the middle of summer in Southern California and everyone is running their air conditioners. Your car could help with grid balancing, so rolling blackouts or other interruptions are avoided. Paradoxically, EVs put enormous strain on our power network as they charge, though in the future, their batteries will also help strengthen our electrical grid. This sounds counterintuitive, but here’s how this would work.

V2G allows electric vehicles to function as mobile energy storage systems, so if your car is parked in the garage, it can feed electricity into your home or you can sell it back to the power company to help keep the lights on, eventually eliminating the need for so-called “peaker plants,” costly and polluting power-generating stations that kick on during periods of high electricity demand.

Thanks to EV batteries, energy storage is already in place, but the bigger issue to making all this work is that power companies need to enable bi-directional charging, plus consumers have to install the appropriate hardware at home, which isn’t necessarily cheap.

You Need to be Connected for Bi-Directional Charging to Work

Bi-directional charging will be supported by WiTricity’s wireless EV chargers. The chargers also have the significant advantage of always being connected. With conductive chargers, if you forget to plug in your EV, there’s no way it can power your home.


Craig Cole is Senior Editor at EV Pulse. He brings 15 years of experience to EV Pulse and is a proud member of the Automotive Press Association and the Midwest Automotive Media Association. Check out the EV Pulse YouTube channel here.

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