Electric vehicle charging: how the grid could benefit

Electric vehicles are essentially batteries on wheels. Figuring out how to charge them not only for mobility, but also to bring electricity back to the grid will be one of the challenges of the next decade.

But doing this, let alone scaling it to the masses, is more complicated than it seems. The technology — known as bi-directional charging — will depend on coordination from policymakers and utilities, as well as help from automakers. If they team up, bi-directional charging could attract potential EV customers who would benefit both financially and reassuringly.

What is bi-directional charging?

To charge an electric vehicle, the charger or car must have a converter that takes alternating current (AC) from the grid and converts it to direct current (DC) that the car’s battery can store. Bi-directional charging technology, which in turn resides either in the car itself or in an external charger, can convert this direct current into alternating current to feed it back into the grid.

Despite its apparent simplicity, the technology is still in the pilot phase, in part because harnessing the power stored in an electric vehicle’s battery requires onboard utilities to feed power back into the grid. California utility PG&E launched several projects last summer to explore the use of bi-directional charging in different contexts and assess how cost-effective the technology is.

Why should we use electric vehicles to power homes or the grid? Is that even a good idea?

There are a number of reasons to use bi-directional charging, but they mostly fall into two buckets: leaving the lights on and making money. Both are pretty good ideas!

Charging vehicles at home gives homeowners more control over their energy use, allowing them to, for example, power their home during a power outage caused by a storm, or use their EV battery for power when electricity prices – which fluctuate throughout the day – fluctuate at their highest point. There’s a wide range in how much power a single EV battery can hold, but a sedan like the Nissan Leaf has a capacity of 40 to 62 kilowatt hours, while a typical US home uses around 30 kWh daily. This means that it is well within the realm of possibility to power a home during an all-day power outage.

Vehicle-to-grid charging requires more coordination with utilities. Storage is becoming increasingly important to smooth out the energy supply spikes and troughs associated with renewable energy, and a parked EV represents a potentially valuable storage resource for utility companies. To unlock this resource, each individual EV must be connected to the grid and then a Software can be used that can assess demand and communicate with utilities.

EV drivers who plug their vehicles into the grid could expect a payday that could help offset the cost of the car itself. In a 2021 National Grid pilot, a Nissan Leaf owner made $4,200 over the course of a single summer by bringing power back to the grid when demand increased. It could be particularly lucrative for fleet owners to feed electricity into the grid in times of need.

How far away is widespread bi-directional charging?

According to Katherine Stainken, vice president for policy at the Electrification Coalition, the biggest obstacle to widespread adoption is that utilities and the state commissions that regulate them are slow to move and cautious about change. Even states like California, which started looking at charging vehicles to the grid a few years ago, are only now figuring out how incentives for EV owners will be structured and what metering technology will be required. Stainken expects these programs to be widely used in the next three to five years.

Home vehicle charging is about to be prime-time ready, although the technology to integrate bi-directional charging into a home’s energy system is not yet widely available. There are a handful of companies — including Emporia and Wallbox — that are coming to market with the technology that could make them a broader reality within the next year.

However, there is one caveat: using an electric vehicle to power a home or the grid is dependent on whether the local utility company allows it. An EV owner cannot sell power back to the grid unless the utility has a program to receive it, and getting power to one’s home depends on having a system in place that tells the utility to stem the flow electricity from the grid.

It’s possible that utility companies are actively getting in the way of vehicle-to-grid charging; You may not want to pay customers for the energy they provide. Florida Power & Light has resisted allowing solar rooftop owners to sell their excess electricity back to the grid, which would entail a similar demand-response program.

Are there any policies that might encourage the use of the technology?

The current landscape of two-way charging policies is fragmented, although federal and state lawmakers are beginning to push utility commissions to create plans for charging vehicles to the grid. For example, in 2020, the California Public Utilities Commission established a framework for vehicle-grid integration after lawmakers required the agency to do so.

There is no federal law or regulation on bi-directional charging, although the bipartisan Infrastructure Act required states to consider how to electrify transportation and change utility tariffs to “encourage affordable and equitable EV charging.” Stainken said this could provide an opportunity for states to create more robust vehicle-to-grid policies, although the law does not penalize states that omit this process.

Working with nonprofit energy security organization SAFE, the Electrification Coalition recommended federal lawmakers expand the charging infrastructure tax credit to cover vehicle-to-grid development and encourage the creation of national technical standards. The latter would require coordination with standard-setting bodies such as UL or SAE to provide automakers with a roadmap to ensure vehicles can handle bi-directional charging.

For its part, the Department of Energy began investigating best practices for accelerating the use of these technologies earlier this year.


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