EV charging stations and V2G

Besides explosive sales growth, one of the most exciting developments in EVs is their potential to give back to the grid. Using your electric vehicle (EV) to commute is one thing. With smart charge technology,  your battery charges anytime. This is the basic premise behind your EV charging station. During off-peak hours (overnight), the battery gets charged cheaply.

Tesla Powerwall, Generac, or Enphase batteries can charge your home backup system the same way.

Now what if a group of EV batteries could shift energy distribution in your neighborhood? The EV microgrid is a few years away but represents a massive shift in how energy can balance the grid and augment or replace expensive battery farms.

Today we’ll share an overview of vehicle-to-grid (V2G) bi-directional charging stations and the potential for powering your home with an EV.

We wrote about solar microgrids in a previous blog. Basically, a microgrid retains power in your micro-community. So during a power blackout, you can keep the lights (or refrigerator) running using a virtual neighborhood power plant.

Consumer EV sales are growing. Delivery fleets are shifting to electric power. Amazon ordered about 100,000 e-trucks manufactured by Rivian in Normal, Illinois. Despite the hype earlier this year, only 10% of the US Postal Service’s new fleet will be electric.

Nissan Leaf at Hancher Auditorium
The Leaf has bi-directional charging capability.

But how much electricity can be stored in EVs?

Rivian’s e-truck for Amazon has a 180kWh lithium-ion battery. But let’s use a Tesla car for this exercise. Tesla’s Model X has a 100kWh battery.

By 2030, experts estimate that about 20 million EVs will be on the road.

20 million EVs times their 100kWh capacity equals 2 tWh. That’s terawatts. The average US home uses almost 30kWh daily. So 20 million EVs with 100kWh batteries could power almost 70 million US homes. Of course, this is all fanciful thinking. Sometimes the cars are on the road. They’re unavailable to power the grid or run your house.

But the bigger hurdle is bi-directional charging. Tesla cars don’t have bi-directional charging capability. Few EVs have it. Volkswagen just announced they would make the technology standard in their cars starting in 2022.

In 2013, Nissan put bi-directional charging into its line of Leaf cars. Fiat, VW, and Audi will follow in the next few years in their EVs.

Fiat 500 at EV charging station
The Fiat 500 will have built-in bi-directional charging technology.

In 2020, Highland Electric Transportation and Proterra partnered to create an electric school bus fleet in Massachusetts. The fleet will employ V2G charging to save money for the school district in Beverly, MA.

Electric school buses cost about $120,000 more than a diesel bus. But in the long run, they save around $200,000 in fuel and maintenance costs. Electric busing was studied by the US Public Interest Research Group (USPIRG) in their 2018 report, “Paying for Electric Busing: Financing Tools for Cities and Agencies to Ditch Diesel.” The report highlights the opportunity for V2G financing to transition to electric fleets.

So bi-directional charging in the car is a piece of V2G. But what else is needed for EV charging stations to create impactful V2G?

How do we transition to V2G?

Beyond making EVs bi-drectional, the system at your house needs to have the two-way technology too. You can’t just send electricity back to the grid. It’s dangerous for utility line-workers.

So your home battery system must be able to easily disconnect from the grid altogether. Another way to put it is that any distributed-generation solar array must have anti-islanding technology.

The benefit of the V2G concept is that it can balance the constantly fluctuating demand in the grid.

The challenge is to bring utility companies onboard and make the grid accessible for solar and distributed energy microgrids like V2G networks.

“Dumb” charging vs smart EV charging stations

With a dumb charger, you plug it in without thinking. Immediately, the car starts charging. No questions asked and no concerns about peak hours (higher priced electricity) or TOU (time-of-use).

At a smart charging station, the EV waits for lower priced electricity, usually overnight, to reduce your bill. The smart charger might also trickle charge (slow) to top it off in time for your commute instead of just sitting around fully charged at 2 a.m.

An even smarter EV charging station waits for an uptick in renewable energy on the grid. In that system, your car consumes less fossil fuel (if you live in a coal- or gas-powered area). That’s the goal isn’t it?

What about V2G?

Bi-directional charging can work two ways, V2G and V2H. EV to grid is V2G. In the other mode, vehicle-to-home (V2H), your car battery discharges overnight to keep the microwave clock running.

V2H can be thought of as a replacement for a Tesla Powerwall or Generac PWRcell battery setup. Instead of a stationary battery bank in your garage or basement, yours has four wheels and can transport groceries.

EV charging stations and V2G

Currently, we have V1G, grid to car. This unidirectional mode of energy transfer can top off your Tesla (or Fisker or Hummer EV) “tank.” But it stops there.

This year, Volkswagen announced V2G begins in 2022. Metaphorically, electric charging stations that accommodate bi-directional power will give VWs a lot of power. A V2G battery network can stabilize the grid, power the household, or charge other EVs.

Think of V2G as a distributed (and mobile) battery farm.

How does V2G work?

When a vehicle is plugged in, V2G software automatically takes control of the vehicle’s charging and discharging. The reserve capacity on the aggregated battery fleet is bid on the grid market. The software guarantees a fully charged EV by morning.

V2G technology has spread in the last few years. Nuvve, a San Diego green energy company, installed a V2G fleet in Denmark in 2016 and capitalized on energy market bidding. The company estimated a $2,000 income from each vehicle in a fleet.

But most expect V2G is several years from widespread adoption. In this writer’s opinion, it is at least a decade from being deployed at scale in the US.

Battery Life

What VW is doing with bi-directional technology may decrease the life of an EV battery. But it might not! Researchers in the UK produced a V2G model that minimizes degradation of EV batteries.

The big issue with battery life is cycles. How many times can a battery be charged and discharged? There’s a limit and after a certain point, you might not have enough juice to commute.

Self-evidently, wind is intermittent. Many politicians love to point it out over and over. Yes, senator, we are aware that the sun is sometimes obscured by clouds too. At these times, the utility company must produce power from another source. Maybe it’s a battery farm or a nuclear plant, maybe it’s a peaker plant, powered by coal or gas.

And maybe someday it’ll be a fleet of electric vehicles networked together.

Or maybe it will be a used EV battery. We wrote a blog about recycling solar panels.

There’s also a growing demand for recycling lithium-ion batteries. A 2021 report from the Union of Concerned Scientists states that there are only about a dozen EV battery recyclers in the world. Today, these recyclers can handle about 10% of the global supply of batteries. But by 2030, that capacity corresponds to only 1% of projected demand for battery recycling.

After an EV battery loses capacity, some scientists suggest their placement in home storage systems makes solar more affordable. Researchers at Utah State University have a solution for EV waste that turns used batteries into solar storage.

Batteries extracted from EVs and installed for stationary use saves dollars and makes sense. The short version: this prolongs the life of a battery.

Want to learn how to charge a Tesla?

Ride along with Merv from VERV Auto in this quick overview of battery charging.

Good to go? V2G, smart charging, and EV stations

Previously, we wrote about the future of EV transportation, the battery boom, and community solar in these blogs.

Do you have an idea for a MOXIE Solar blog? Write to us at or join the discussion on Facebook, LinkedIn, and Twitter.

Share this post