Plug and Charge is a method of automatic authentication and billing at public chargers in which the electric vehicle identifies itself to the charging station with a digital contract certificate, so charging starts as soon as the cable is connected, without a card, app or payment terminal. In EV charging, Plug and Charge is defined by the ISO 15118 standard and relies on a public key infrastructure that links vehicle makers, charging operators and mobility service providers.
The feature removes the most common source of friction at public chargers: finding the right app or RFID card for each network. Its real-world usefulness, however, depends on whether the vehicle, the charger, the operator’s back end and the driver’s contract all support it.
How a Plug and Charge session works
When the connector is plugged in, the vehicle and the charger establish high-level communication over the charging cable using power line communication on the control pilot line. They open an encrypted TLS connection, with the charger proving its identity with its own certificate.
The vehicle then presents its contract certificate, which identifies the driver’s charging contract with a mobility service provider. The charger forwards it to the operator’s back end, typically over OCPP, which validates the certificate chain and checks with the provider that the contract is active. Once authorized, power flows and the session is billed to the contract automatically.
| Step | What happens | Main participants |
|---|---|---|
| 1. Connection | Cable plugged in, communication link set up | Vehicle and charger |
| 2. Secure channel | TLS session established | Vehicle and charger |
| 3. Identification | Vehicle sends its contract certificate | Vehicle |
| 4. Authorization | Certificate and contract validated | Charge point operator and service provider |
| 5. Charging and billing | Energy delivered, session recorded | All parties |
The certificates behind Plug and Charge
Plug and Charge rests on a public key infrastructure (PKI) in which each role holds certificates traceable to a trusted root. The V2G root certificate anchors trust; for interoperability across networks, providers rely on a common root or on cross-recognized roots managed by ecosystem operators.
| Certificate | Held by | Purpose |
|---|---|---|
| V2G root certificate | Vehicles and chargers as a trust anchor | Validates every other certificate |
| Charger certificate | Each charging station | Proves the charger is genuine |
| OEM provisioning certificate | Vehicle, installed at production | Lets the car request its contract certificate |
| Contract certificate | Vehicle, issued by the service provider | Identifies the driver’s charging contract |
Contract certificates have a limited validity, often one to two years, and are renewed over the air or through the charger. If a certificate expires or is revoked, the vehicle falls back to manual authorization.
Plug and Charge compared with other ways to start a session
Plug and Charge competes with several older and simpler methods. The table places it among them.
| Method | How it identifies the driver | Security level | Convenience |
|---|---|---|---|
| Plug and Charge | Contract certificate in the vehicle | High, encrypted and signed | Very high |
| RFID card | Card identifier read at the charger | Low to moderate, cards can be cloned | Moderate |
| Smartphone app | Account login and QR code | Moderate | Low to moderate |
| Ad hoc card payment | Credit or debit card terminal | High | Moderate |
| Autocharge | Vehicle hardware address | Low, easy to spoof | High |
Autocharge offers a similar experience by recognizing a vehicle’s communication controller address, but it uses no cryptography and cannot handle multiple contracts. Some vehicle makers also run proprietary automatic charging on their own networks, which feels identical to the driver but works only within that ecosystem.
Requirements and practical setup
Plug and Charge works only when every link in the chain supports it. A missing element at any point means the session falls back to app or card authorization.
- A capable vehicle with ISO 15118 communication and an installed provisioning certificate.
- A capable charger running firmware with ISO 15118 and the matching root certificates.
- An operator back end that forwards certificates, often through OCPP 2.0.1 or extensions to OCPP 1.6.
- A service contract from a mobility service provider that issues contract certificates.
- Activation by the driver, usually in the vehicle’s app or infotainment menu.
Support today is strongest at DC fast chargers of large networks. The newer ISO 15118-20 edition allows several contracts per vehicle and extends Plug and Charge to wireless and bidirectional charging, but adoption takes years because both cars and chargers need updates.
Limitations and common problems
The most frequent issues stem from the complexity of the trust chain, not from the charging hardware itself.
- Unclear pricing, because the tariff comes from the driver’s contract and may not be shown at the charger.
- Failed sessions after updates, when root certificates on chargers or vehicles are out of date.
- One contract per vehicle in older implementations, which complicates shared or company cars.
- Patchy roaming support, since not all networks accept certificates from all providers.
Privacy is a further consideration. Because the contract certificate identifies the same contract at every session, charging behavior can be linked to one vehicle across operators. The data is protected in transit, but drivers and fleet managers should understand which providers receive session records and how long they keep them. When a session fails without explanation, a practical first check is whether the contract certificate is still valid in the vehicle menu, followed by a test at another charger of the same network to separate a vehicle problem from a station problem.
The simple explanation
Plug and Charge means plugging in is all a driver needs to do. The car carries a kind of digital membership card. When the cable is connected, the car shows that card to the charger, the charger checks it with the company that issued it, and charging starts. The bill goes to the driver’s account automatically.
It is similar to a toll tag on a highway: the system recognizes the car and handles payment in the background. It only works if the car, the charger and the charging contract all support it; otherwise, the driver uses an app or card as usual.
How it is used in practice
A sales representative drives about 40,000 km a year across several countries in a company electric car. Previously, every stop at a fast charger meant opening one of several apps, often in poor mobile coverage, and occasionally waiting several minutes for a session to start.
The company activates Plug and Charge in the car’s settings, linked to a fleet charging contract that roams across major networks. At supporting stations, the representative now plugs in and charging begins within seconds. The company receives one monthly invoice covering all sessions. At about one in five stops the charger does not yet support the feature, and the driver falls back to the fleet RFID card, which remains in the glovebox for that reason.