Plug and Charge Explained: ISO 15118, DIN SPEC 70121, Tesla and Why Not All EV Charging Is the Same

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Plug and Charge is often described as the holy grail of EV charging. Plug in the vehicle, walk away, and charging plus payment just happen. No apps, no cards, no fiddly screens.

The problem is that not all Plug and Charge is the same. The term is used to describe several very different technical approaches, each with different implications for drivers, fleets and chargepoint operators.

This matters. Especially for fleets relying on EV charging payment at scale, and for CPOs integrating with roaming partners like Paua.

This guide explains the four main types of Plug and Charge in the market today, what they really mean, and why Paua has been testing Plug and Charge experiences since August 2021.

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What is Plug and Charge in EV charging?

At its simplest, Plug and Charge means:

• A driver plugs in an EV
• Charging starts automatically
• Payment is handled in the background

For drivers and fleet managers, that is all that matters.

Under the bonnet, however, Plug and Charge can be delivered through very different mechanisms, ranging from open standards to proprietary systems and intelligent software overlays.

Understanding those differences is key to making the right infrastructure and partnership decisions.

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The four types of Plug and Charge explained

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1. Digital proximity based Plug and Charge

Paua, launched August 2021

In August 2021, Paua successfully trialled a Plug and Charge solution designed to work across all modern electric vehicles and public chargepoints.

Rather than relying on emerging vehicle standards or closed ecosystems, Paua used:

• Pre-registration of the driver
• Proximity and contextual data
• Charger status and location intelligence
• A proprietary authorisation algorithm

The result was a true Plug and Charge experience:

• No app
• No RFID card
• No charger interaction
• Automatic EV charging payment

The solution was demonstrated at a Mer EV fast AC charger in Reading using a Renault Zoe and was designed to work across AC and DC infrastructure.

What made this approach distinctive was interoperability. Paua’s Plug and Charge:

• Was vehicle agnostic
• Was network agnostic
• Worked on kerbside chargers and rapid chargers
• Did not require ISO 15118 support

This aligned directly with UK Government objectives to reduce friction in public EV charging and accelerate fleet electrification. Paua developed the technology with support from the Department for Transport through the T-TRIG scheme, delivered by Connected Places Catapult.

The philosophy was simple. Remove complexity for drivers and absorb it into software.

However technical challenges meant that this was not extensively scaled.

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2. ISO 15118 Plug and Charge

The industry gold standard

ISO 15118 is the most fully featured Plug and Charge standard.

It enables:

• Secure certificate based authentication
• Encrypted communication using TLS
• Automatic contract handling
• Smart charging and energy management
• Support for both AC and DC charging

When fully implemented, ISO 15118 delivers a superb experience and is widely regarded as the long-term direction of travel for the industry.

However, adoption is still uneven:

• Not all vehicles support ISO 15118
• Not all chargepoints support ISO 15118
• Certificate management remains complex

For fleet operators and CPOs, ISO 15118 is powerful but not yet universal. It works best where vehicles, chargers and backend systems are tightly aligned.

Paua is working towards this standard with the support of Hubject.

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3. DIN SPEC 70121

Auto charge, but not full Plug and Charge

DIN SPEC 70121 is often confused with ISO 15118, but they are not the same.

DIN SPEC 70121:

• Applies to DC charging only
• Is based on an early draft of ISO 15118
• Enables basic vehicle to charger communication

What it does not provide is true Plug and Charge security. DIN SPEC 70121 lacks:

• Digital certificates
• Transport Layer Security
• Cryptographic signatures
• Smart charging functionality

As a result, DIN SPEC 70121 can enable automatic charging behaviour, but it does not meet the security or flexibility requirements of modern EV charging payment at scale.

It was created as a transitional standard and its role is diminishing as ISO 15118 matures.

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4. Tesla’s proprietary Plug and Charge

Seamless, but closed

Tesla demonstrated Plug and Charge before the rest of the industry caught up.

The experience is excellent:

• Plug in
• Walk away
• Automatic billing

The limitation is scope. Tesla’s Plug and Charge:

• Only works for Tesla vehicles
• Only works on Tesla infrastructure
• Is not interoperable with wider networks

For mixed fleets and public charging ecosystems, this proprietary approach does not scale.

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Why not all Plug and Charge is equal

From the driver’s perspective, all four approaches feel similar.
From a systems perspective, they are fundamentally different.

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For fleets using EV charge cards and roaming networks, interoperability matters as much as convenience.

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Paua’s approach to Plug and Charge

Paua’s role in the EV ecosystem is to simplify EV charging payment for fleets.

That means:

• Delivering a frictionless experience today
• Supporting all modern electric vehicles
• Working across the widest possible charging network
• Remaining compatible with future standards

Paua does not view ISO 15118 as a competitor to its Plug and Charge approach we tested previoulsy. Instead, it is complementary, and has the advantage of potential significant scale.

As standards mature and adoption increases, Paua can incorporate them. Until then, fleets and drivers still benefit from a seamless experience across the UK’s largest aggregated charging network.

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What this means for fleets and CPOs

Drivers do not care which standard authenticates the charge.
Fleet managers care about reliability, reporting and cost control.
CPOs care about utilisation, roaming revenue and operational simplicity.

Plug and Charge is not one technology. It is a spectrum of approaches.

Paua sits above that complexity to deliver the outcome everyone wants.
Plug in. Charge. Go.

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