Vehicle-to-Grid (V2G) Charging

BorgWarner delivers the only UL-Certified bi-directional V2G capable chargers in the market

Vehicle-to-grid (V2G) technology adds resiliency to the power grid and provides revenue-making opportunities for electric school bus and commercial fleet operators.

The technology allows electric vehicles to store energy from the grid and return it to the grid when it is needed, allowing for a more reliable and efficient power grid. Additionally, V2G technology helps reduce carbon emissions and enables school buses and commercial fleet operators to monetize their electric vehicles.

By connecting their vehicles to the grid, fleet operators can earn money from energy providers for providing energy back to the grid during peak times. This helps reduce the strain on the grid and enables energy providers to meet demand more efficiently.

Made in the USA

Applicable for securing government funding.

Charging for All Vehicles

DC fast chargers designed for convenient charging of electric vehicle models from passenger vehicles to heavy-duty equipment with high-voltage battery systems.

Scalable Design

Individual modules for the PCS and dispenser facilitates future expansion and easy site layout planning.

Flexible Mounting

Floor/pedestal or wall-mounted dispenser options.

Certified Bidirectional

BorgWarner chargers are UL-certified bi-directional chargers for V2G applications.

Wide Range

A wide output voltage range of 270 – 920 makes our chargers ready to handle batteries of all sizes.

Exploring the Use Cases for Vehicle-to-Grid (V2G)

One use case (or set of use cases) that we didn’t explore in our EV charging blog series is that of Vehicle-to-Grid (V2G).  The concept of V2G is straightforward – it allows energy to be taken from vehicles and put back onto the grid.There are two main scenarios of interest for V2G:

  • Using vehicle power to mitigate the impact of peak usage on both the grid (reduced generation needs) and on energy prices (lower bills because of peak usage); and
  • Using vehicle power to establish a grid (typically for a critical building) during power outages; this is known as vehicle-to-building (V2B).

Looking primarily at V2G for fleets, since V2B is generally an “emergency” condition. While any EV could theoretically be utilized for V2G (or V2B), the vehicles that are of most interest are medium- and heavy-duty (M/HD) EVs.

As to be read in this section, these M/HD EVs have significantbattery capacity (150kWh to well over 600kWh), the fleets have robust DC fast charging infrastructure (with charging capacities of 60kW up to 500kW), and fleet operating hours that are generally complimentary to peak hours. A recent study by the USPublic Interest Group (US PIRG) has predicted that V2G can reduce the lifecycle costs of an electric school bus by up to $130,000; with a 12-year lifespan, that is about $11,000/year.

The two primary impacts that V2G has on M/HD EV usecases are: i) it potentially shortens the window for charging; and ii) during this shorter window, the vehicles of interest may need to be fully charged. We say “potentially shorter window” because in most cases, fleets avoid chargingduring peak usage hours because of the increased energy costs. The impact of having to fully recharge a vehicle is easier to quantify. With a charging window of 9pm-5am (8 hours), a 675kW public transit bus would need a charger that can put nearly85 kW of power into the bus per hour. Since these vehicles are generally run to 80%-90% of their battery capacity (68kWh-100kWh of remaining charge), V2G requires an increase in charging capacity of roughly 10 kW (i.e., a non-V2G bus could utilizea 75kW charger vs the 85kW charger needed for V2G). For an electric school bus, V2G would increase the charging required from 125kWh in non-V2G mode to 150kWh in V2G mode – an increase of 25kWh, or 3kW per hour over an 8-hour charging window.In both the public transit bus and school bus use cases, the impact of V2G is relatively small – an increase in charger capacity of only 10%- 17%. Of course, the main requirement is that the charger can operate in bidirectional mode.

Our market-leading bi-directional EV charging systems (which are designed from the start for the needs of fleet operators) are designed and built in the USA. BorgWarner also excels in the design of high-power smart inverters for next-generationrenewable energy and energy storage deployments. Our expertise in energy management system (EMS) software is also embedded in our VectorStat EMS controller and software which is embedded in our EV charging systems and smart inverters. We have builtover a thousand V2G-capable high-power, high-reliability chargers and bi-directional smart inverters for a variety of different sizes and classes of EVs.

Vehicle-to-Grid (V2G) Solution Brief

V2G Improves Total Cost of Fleet Ownership and Grid Resilience

The future of EV infrastructures will include Vehicle-to-Grid (V2G) capabilities using bi-directional chargers to reduce the cost of fleet ownership and improve grid stability. Fleet vehicles are uniquely suited to V2G applications due mainly to predictable usage patterns and the fact that they often return to base at the end of the working day, where they sit idle overnight. Regular charging patterns provide the perfect condition for V2G applications by allowing the use of stored energy during specific periods while planning enough time to charge vehicles again for the next day.  This will be a crucial feature for reducing the cost of fleet ownership by enabling fleets to sell energy, including from renewable sources, back into the grid.

Financial Impact

V2G takes the unused energy in an EV’s battery, puts it back onto the grid during peak demand hours, and then recharges the vehicle during off-peak hours (typically 9pm-9am). The energy put back onto the grid during on-peak time of use (TOU) hours allows the vehicle operator to get a premium for that energy and recharge at cheaper rates.  As an example of potential cost savings, San Diego Gas & Electric (SDG&E) charges less than $0.24 per kWh during super off-peak TOU and almost $0.60 per kWh during on-peak TOU, double the price (prices from June 1, 2022, Time-of-Use Plans).

The impact of V2G on electric vehicle fleet energy costs can be substantial, but the impact on the choice of EV charging infrastructure is also noteworthy. This is because both the energy used by the vehicle and the energy put back onto the grid during peak hours must be recovered to charge the vehicle fully. Maximizing infrastructure uptime is critical for a successful implementation. Considerations for selecting capable electric vehicle supply equipment (EVSE) for a V2G infrastructure are listed further in this article.

Grid Resilience

Both extreme weather and peak loads constantly challenge the utility grid’s resilience. Recent events underline the need for backup power storage, such as Hurricane Katrina, Hurricane Ida, Hurricane Sandy, Hurricane Sally, the Texas cold snap of 2021, and the extreme heatwave of 2022. Power outages during these events reveal vulnerabilities of our emergency power systems which can be critical hospitals, nursing homes, and other healthcare facilities. The potential power available from EV fleets can help manage disruptions as they unfold and mitigate the impact of power outages on communities. Utilities realize V2G potential for adding grid stability and are implementing incentives for fleets. For example, Pacific Gas & Electric (PG&E) is planning to pay up to $2 per kWh for emergency use.

V2G Infrastructure Considerations

Fleet operators must consider several factors when planning a V2G-capable charging infrastructure. Equipment is the first consideration. Fleets must be equipped with vehicles and Electric Vehicle Supply Equipment (EVSE) that support bidirectional charging. Operators will need UL 1741-SA certified Level 3 DC fast chargers (DCFC), such as displayed here, which run on 480 3-phase power.

Fleet operators should also reach out to a utility rep to find out about any potential upgrades that may be required because of the new loads from EVSE, such as a new service line or an upgraded distribution transformer. Your local utility may offer EVSE rebates to reduce the capital cost, so it’s important to contact a rep early in the V2G infrastructure planning process.

Other considerations include determining site layout, future planning, and steps to mitigate installation costs.

V2G Diagram Fleet

The Impact of Charger Reliability on the V2G Use Case for M/HD EVs

V2G can have an impact on reducing the total cost of ownership (TCO) for medium- and heavy-duty (M/HD) electric vehicle (EV) fleets (Read article here). Now looking at the impact that charger reliability can have on M/HD EV fleets that employ V2G to reduce their TCO. Let’s start with “what does it mean to have a 1% drop in charger reliability for M/HD EV fleets?” An 8-hour per day charging window and 260 charging days annually results in a total of 2,080 charging hours per year. The straightforward math would say that a 1% charger outage reduces charger availability by 21 hours. However, V2G chargers must also operate during the 4-hour peak usage time, where they put power back onto the grid, essentially increasing their usage by 50% to 3,120 operating hours per year; 1% of this now becomes 31 hours. This is nearly 3 days of downtime. To this must be added the time to service the charger, which could itself be at least a day per outage (and in some cases as much as 2 days per outage). Assuming that the three days of downtime above are not concurrent but are isolated from each other, AND assuming an average of 1.5 days to service each outage results in 7.5 days, or an effective non-availability percentage of 2.8%.

Now imagine a reduction in reliability from 99% to 95% (a 4% reduction!). Given the assumptions above about servicing, this would represent a non-availability of 30 days, or a percentage of 11.2%. For a school bus, this would impact V2G’s TCO reduction ($130,000 according to the US PIRG) by $14,560 (and this is on top of the impact of reliability of unidirectional chargers on fleet EV costs). Unfortunately, a reliability rate of 95% is more the norm than not for “commercial” chargers today (those that charge private autos in multi-family or mixed-use settings), and their reliability when charging M/HD EVs (which have a significantly higher charging cycle than private autos) would be even less. This represent real and significant costs over the lifetime of a M/HD EV fleet, especially for a fleet utilizing V2G.

V2G Infrastructure Planning – Top 3 Considerations

Using Vehicle-to-Grid (V2G) technology, commercial EV fleet operators can support grid resiliency and maximize renewable energy sources while adding monetization opportunities by selling energy back to utilities. V2G essentially allows fleets to store energy in EV batteries and discharge it back into the grid. Using the additional energy source from fleet EVs can help stabilize energy conditions, provide power in emergencies, and alleviate the need to start up additional energy and power sources.

The energy fleet operators can provide to the grid, or buildings could offer revenue. BorgWarner chargers are successfully supporting several V2G testing programs, and each commercial EV has the potential to make thousands of dollars per commercial EV. Through successful testing and V2G pilot programs, we uncovered three implementation considerations when creating a full-scale V2G fleet infrastructure.

Site Layout and Future Planning

Our DC Fast Chargers are designed for fleets of all types and leverages installed V2G charger to provide energy and power when needed –  no new infrastructure. Fleet operators should consider site layout for future planning when developing a V2G charging depo. Taking steps during the initial layout phase to accommodate future fleet growth will substantially mitigate installation costs for the additional units. BorgWarner chargers can be installed in a daisy-chain wiring architecture so that a single charger can accommodate up to five power dispensers or in a 1:1 Power converter: dispenser ratio to maximize power/energy delivery back to the grid or critical load. Even if you only need two charging spots now, you can plan and layout your depot floorplan to provide enough space to add three chargers when your fleet grows incrementally.

Commercial EV and EVSE

Equipment is the crucial consideration to make V2G work. Fleets must be equipped with Electric Vehicles (EVs) and Electric Vehicle Supply Equipment (EVSE) that support bidirectional charging. Operators will need UL 1741-SA certified Level 3 DC fast chargers (DCFC), such as RES-DCVC125-480 chargers and RES-D3-CS20 dispensers, which run on 480 3-phase power.  Both vehicles and charger will need to support a compatible discharge protocol.   Emerging into the market is the ISO15118-20, the follow-on to ISO15118-2 edition 2.  -20 enables a standard method for V2G.  both vehicle  and charger  must support this standard.

Utility Relationship/Interconnect Agreement 

Reach out to the utility early with plans and power requirements.  Like when a home with solar power sells excess power back to the grid, a utility interconnect agreement must be in place. Fleet operators should also reach out to a utility rep to establish an interconnect agreement that ensures they will buy power back. Utility reps will provide information about potential upgrades that may be required because of the new loads from EVSE, such as a new service line or an upgraded distribution transformer. Your local utility may also offer EVSE rebates to reduce the capital cost, so it’s recommended that you contact a rep early in the V2G infrastructure planning process. Other considerations include:

  • Selecting a utility aggregator
  • Determine utility incentives for EV infrastructure and discharge
  • Identifying V2G compliant vehicles
  • Determining site layout
  • Future planning
  • Steps to mitigate installation costs

Once the system is in place, both fleet operators and their local grid will reap the long-term benefits afforded by this novel technology.

Case Study: Pioneering Commercial Vehicle-To-Grid in Electric School Buses

In the summers of 2021 & 2022, Highland Electric Fleets & BorgWarner used vehicle-to-grid (V2G) technology to discharge 10+ MWh hours to the Massachusetts grid over 158 hours -- the first time battery storage from electric school buses (ESBs) was used in a commercial V2G program in the United States. Participation generated $23k in revenue and demonstrates the value ESBs can deliver to support the grid and lower the cost of ownership of an electric bus fleet.

Download Case Study as PDF

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