Overview

Explaining V2X

In this new world of connecting electric vehicles to the grid, there is a lot of jargon created that makes sense to everyone working on it at the time, but tends to confuse everyone else not involved.

Throughout this website I use V2H for simplicity and because it's my favorite application.

Here is an overview of the different terms you may run into and how they differ

V2G - Vehicle to Grid

Interconnecting an EV to the grid and the ability to charge and discharge a battery for for grid services, turning the vehicle into a Distributed Energy Resource (DER) while it's parked. These grid services can include wholesale market operations like frequency regulation and real-time pricing or distribution level services like Demand Response (DR).


V2H - Vehicle to Home

This is a residential application to use an EV at home. The energy services are poorly defined here, but most people assume of emergency back up power as the main function (even though many EVs and products can't peform this function).


V2B - Vehicle to building

Not a well defined term, but refers to commercial building applications which required higher power and different voltages. It also suggests energy services typical for commercial accounts such as demand charge management (DCM) and Time of Use (TOU) rate arbitrage, but this is not clearly defined either. For some reason many people assume this is less complex than V2G, but requires all the same certification, functionality and interconnection, causing this acronym to do more harm than good.


V2L - Vehicle to Load

This is using the vehicle as a power source for an independent load like power tools, appliances or other systems not connected to the grid. Think of this like plugging something into to your cigarette lighter but being able to get 100x the power out of it.


V2X - Vehicle to Everything

This is supposed to encompass all these variations, but usually gets confused with with C-V2X, the vehicle to infrastructure technology that refer to systems that connect vehicles with street lights and other traffic systems.


VGI - Vehicle Grid Integration

This is a California invented term that encompasses all aspects of a vehicle connected to the grid. In short, V1G and V2G is VGI.


V1G - Smart charging

Unidirectional charging. This is insider jargon as a play on words the acronym V2G. Only controlling the charge rate, not discharging the vehicle


V2V - Vehicle to Vehicle

Sharing energy between vehicles.


VTG - Vehicle to Grid

I’ve seen European colleagues use this instead of V2G. Perhaps V2G only works well in the English language.


ePTO - Electric Power Take-Off

Similar to V2L, but usually for Heavy Duty vehicles, and not limited to an EV.


BPT - Bidirectional Power Transfer

Used in standards langauge

Other associated terms

Islanding - the ability to disconnect from the grid and power a home independent of the utility.

Blackstart - an additional battery that can power a system on in a power outage.

Interconnection - Approval from the utility to be connected to the grid. This is required even if power is not planned to be exported. A customer is required to obtain a PTO (permission to operate) from the utility if a battery will be connected to the grid.

EVSE - Electric Vehicle Supply Equipment

Fancy word for charging station, as the actual charger may be inside the vehicle or inside the EVSE. See below.

AC-V2G vs. DC-V2G

V2H can get very confusing as there is more than one way to export power from an EV. Batteries store electricity as Direct Current (DC), but our homes and buildings use Alternating Current (AC). That means the battery needs an inverter to be useful. That inverter can sit inside the vehicle as an onboard charger (OBC) or can sit inside the charging station.

AC-V2H refers to a bidirectional onboard charger inside the car.

DC-V2H refers to a bidirectional charging station (or EVSE).

This is imporant, as the inverter is the point of interconnection with the districtuion utility. In the US, most utlities are looking for a safety certification called UL 1741 in order to approve interconnection. Charging stations can get the certification; the industry is still working through how a vehicle could obtain an equivlent certification. This means the main commercial offerings will be DC-V2H for the next few years.

Where the inverter is located matters a lot


source: IEEE

US Charging Standards

How you connect to the EV battery happens through the charging connector. Here are the main connectors and protocols in the US. Recoginize there is a commuinication protocol as well as a plug type that is important for V2H.

Tesla

AC/DC

World of their own and will sell you a Powerwall instead of V2H functionality. No V2H functionality and not planned.


CHAdeMO

DC

This is capable fo V2H and the dominant charging standard in Japan and fading from US and EU


CCS (combo)

DC

Becoming the dominant charging connector in the US, but different version of the charging protocols are currently being used for V2G. In the US these are the standards being implemented for V2G with CCS

DIN 70121

ISO 15118-2

ISO 15118-20

The standards bodies working with CCS have been extremely slow on adding V2G functionality. Surprising it has taken these groups so long as CHAdeMO had this enabled more than ten years ago.

J1772

AC

This is possible to export power via AC, but additional communcations is required. See above for issues of interconnection with and AC system