Myth-busting Charging standards & interoperability (NACS, CCS): separating hype from reality

In January 2026, the UK's Office for Zero Emission Vehicles reported that 14% of all public charging sessions in England failed on the first attempt due to connector or protocol incompatibility, a figure that rises to 23% when drivers attempt to use cross-network roaming (OZEV, 2026). Meanwhile, across the Atlantic, the Society of Automotive Engineers officially published the NACS (North American Charging Standard) as SAE J3400 in late 2024, triggering a wave of automaker adoption that has reshaped the North American charging landscape. For founders building charging hardware, software, or services in the UK and Europe, the rapid evolution of standards creates both opportunity and confusion. Getting the facts right on interoperability is essential.

Why It Matters

The UK government has committed to ending the sale of new petrol and diesel cars by 2035, with the Zero Emission Vehicle (ZEV) mandate requiring 80% of new car sales to be electric by 2030. Meeting these targets depends on a charging network that drivers actually trust and use. The Competition and Markets Authority found in 2024 that unreliable charging experiences were the single largest barrier to EV adoption among UK consumers who had considered but not yet purchased an electric vehicle (CMA, 2024).

Globally, the public EV charging market is projected to reach $111 billion by 2030, according to BloombergNEF. In the UK alone, approximately 300,000 public charge points will be needed by 2030, up from roughly 73,000 installed as of early 2026 (DfT, 2026). The standards and protocols underpinning these networks determine who can charge where, how fast, and at what cost. Interoperability failures do not just inconvenience individual drivers: they erode public confidence in the entire EV transition and concentrate market power among vertically integrated operators.

Key Concepts

Charging connector standards define the physical plug shape and electrical specifications. CCS (Combined Charging System) is the mandated standard across the EU and UK, with CCS2 (Type 2 combo) being the specific variant used in Europe. NACS, developed by Tesla and now standardised as SAE J3400, is the dominant DC fast-charging connector in North America.

Communication protocols govern how the vehicle and charger exchange information. ISO 15118, commonly called Plug & Charge, enables automatic authentication and payment when a cable is connected. OCPP (Open Charge Point Protocol), maintained by the Open Charge Alliance, standardises communication between charge points and network management systems. OCPI (Open Charge Point Interface) handles roaming agreements between different charging networks, allowing a driver with one network's account to charge on another network's infrastructure.

Interoperability operates at multiple layers: physical (does the plug fit), electrical (can power flow at the right voltage and current), communication (do vehicle and charger negotiate correctly), and commercial (can the driver authenticate and pay). Failures at any layer degrade the user experience.

Myth 1: NACS Will Replace CCS in the UK and Europe

This myth has accelerated since every major North American automaker announced NACS adoption. However, the regulatory and market realities in Europe are fundamentally different. The EU Alternative Fuels Infrastructure Regulation (AFIR), which took effect in April 2024, mandates CCS2 connectors at all publicly funded DC fast-charging stations across the EU. The UK's Public Charge Point Regulations 2023 similarly require CCS compatibility for rapid chargers.

Tesla itself has already converted its entire European Supercharger network to CCS2 connectors. As of early 2026, there is no Tesla vehicle sold in the UK or EU that uses the NACS connector. The installed base of CCS2-compatible vehicles in Europe exceeds 8.5 million, creating overwhelming lock-in (ACEA, 2025).

The practical reality: NACS is a North American standard. UK founders building charging products should design for CCS2 as the mandatory baseline, with awareness of NACS only relevant for products targeting export to North America or serving as adaptor accessories.

Myth 2: Open Protocols Like OCPP Guarantee Interoperability

OCPP has been a significant step forward, but the assumption that OCPP compliance ensures seamless interoperability is incorrect. OCPP 1.6, still the most widely deployed version, leaves substantial room for implementation variation. A 2025 field study by EV Roam, a UK-funded interoperability testing initiative, found that 27% of OCPP 1.6-compliant charge point and backend system pairings exhibited communication failures during testing, including incorrect session state reporting, failed remote start commands, and payment processing errors (EV Roam, 2025).

OCPP 2.0.1, released in 2020 but still in early stages of market adoption, addresses many of these gaps with mandatory message fields, device management capabilities, and ISO 15118 integration. However, the transition is slow: as of Q1 2026, only an estimated 18% of installed UK public charge points run OCPP 2.0.1 (ChargeUK, 2026).

The correction: OCPP compliance is a necessary but insufficient condition for interoperability. Founders should specify OCPP 2.0.1 as a minimum, invest in multi-vendor conformance testing, and participate in interoperability testing programmes such as those run by the Open Charge Alliance and EV Roam.

Myth 3: Plug & Charge Will Eliminate All Payment Friction

ISO 15118 Plug & Charge technology, which enables automated authentication and billing when a cable is connected, is frequently presented as the solution to all charging payment friction. The technology works: BMW, Mercedes-Benz, and Ford have deployed Plug & Charge capabilities in recent models, and Ionity's European network supports the feature across its corridor stations.

However, the rollout has been far slower than anticipated. A 2025 survey by the European Automobile Manufacturers' Association found that only 12% of public DC fast chargers in Europe had fully operational Plug & Charge capability, and only 34% of EVs sold in 2025 shipped with the necessary digital certificates pre-installed (ACEA, 2025). The certificate management infrastructure, which requires coordination between automakers, charging networks, and certificate authorities, remains fragmented.

In the UK specifically, the requirement for contactless payment at all new rapid charge points (introduced under the Public Charge Point Regulations 2023) has created a parallel payment path that reduces the urgency for Plug & Charge deployment. Many UK operators have prioritised contactless terminals over ISO 15118 implementation because the regulatory mandate applies to payment card acceptance, not to Plug & Charge.

The practical takeaway: Plug & Charge will eventually reduce friction for compatible vehicles and networks, but it is not a near-term substitute for robust contactless payment, app-based payment, and ad hoc access mechanisms. Build for multiple payment pathways.

Myth 4: Roaming Agreements Solve the Multi-Network Problem

Roaming, enabled by protocols like OCPI and platforms like Hubject and Gireve, allows drivers to access multiple charging networks through a single account. In theory, roaming eliminates the need for drivers to hold accounts with every network operator. In practice, the experience remains inconsistent.

ChargeUK reported in 2025 that while 78% of UK public charge points were technically accessible via at least one roaming agreement, only 52% of cross-network charging sessions completed without errors on the first attempt (ChargeUK, 2025). Common failure modes included tariff display mismatches (the price shown in the driver's app differing from the price charged), session start failures due to authentication timeouts, and inability to access real-time availability data across networks.

The root cause is not protocol deficiency but commercial and operational fragmentation. Roaming hubs negotiate bilateral agreements between networks, and coverage gaps persist where commercial terms have not been agreed. Some operators deliberately limit roaming to protect their direct customer base.

The correction: roaming is progressing but remains unreliable for end users. Founders building charging software should implement direct integrations with major UK networks alongside roaming hub connections, and should clearly communicate to users when a session is roaming versus direct.

Myth 5: Megawatt Charging for Heavy Vehicles Is Ready for Deployment

The Megawatt Charging System (MCS), designed for electric trucks and buses, is frequently cited as a near-term solution for commercial vehicle electrification. The CharIN MCS specification targets power levels of up to 3.75 MW, which would enable a heavy-duty truck to add 300 km of range in approximately 30 minutes.

However, as of early 2026, no MCS-compliant commercial charging station has been deployed in the UK. Pilot installations exist in Germany (at the National Centre for Charging Infrastructure) and in the US (through the Department of Energy's SuperTruck programme), but these remain test sites, not commercial operations (CharIN, 2025). The grid infrastructure requirements for megawatt-level charging are substantial: a single MCS station with four bays requires grid connections equivalent to a medium-sized industrial facility.

The realistic timeline: commercial MCS deployments in the UK are expected to begin in late 2027 or 2028, initially at depot locations and strategic corridor points. Founders targeting the commercial vehicle charging segment should design for current CCS-based high-power charging (up to 400 kW) while ensuring hardware architectures can accommodate MCS upgrades.

What's Working

The UK's Public Charge Point Regulations 2023 have driven measurable improvements in reliability and payment accessibility. Operators must now provide 99% uptime reporting, offer contactless payment at rapid chargers, and publish real-time availability data through open APIs. Early compliance data shows average rapid charger uptime improving from 92% in 2023 to 95.4% in 2025 (OZEV, 2026).

Ionity's pan-European high-power charging network has demonstrated that multi-brand interoperability at scale is achievable. The network, backed by BMW, Ford, Hyundai, Mercedes-Benz, and Volkswagen Group, operates over 3,200 charging points across 24 countries with consistent CCS2 compatibility and Plug & Charge support.

Octopus Energy's Electroverse platform has emerged as one of the UK's most successful roaming aggregators, providing access to over 700,000 charge points across Europe through a single app and account. The platform's reliability rates for cross-network sessions exceed 88%, meaningfully above the industry average.

What's Not Working

The UK's local authority-led charging procurement model has produced significant postcode lottery effects. Wealthier London boroughs have 40 to 60 public charge points per 10,000 vehicles, while some rural districts in Wales and northern England have fewer than 5 per 10,000 vehicles (DfT, 2026). Standardisation of hardware and software specifications across local authority contracts remains poor.

Bidirectional charging (vehicle-to-grid, or V2G) interoperability standards are still immature. ISO 15118-20, which includes bidirectional power transfer specifications, has been published but implementation is sparse. Only a handful of vehicles (notably the Nissan Leaf via CHAdeMO) currently support V2G in the UK, and no CCS-based V2G deployment has reached commercial scale.

OCPI adoption across UK charge point operators remains uneven. Smaller operators frequently implement partial OCPI support, publishing static location data but failing to provide real-time session management or tariff information through the protocol. This creates a misleading appearance of roaming capability without actual functional interoperability.

Key Players

Established Companies

• CharIN: global industry association governing CCS and MCS standards with over 300 member organisations
• Ionity: pan-European high-power charging network demonstrating multi-brand CCS2 interoperability at scale
• Tesla: converted European Supercharger network to CCS2, driving cross-brand charging access
• ABB E-mobility: leading manufacturer of DC fast chargers with OCPP 2.0.1 and ISO 15118 support

Startups

• Octopus Electroverse: UK-based roaming aggregator providing single-app access to over 700,000 charge points across Europe
• ev.energy: smart charging platform optimising charging sessions across home, workplace, and public networks
• Monta: Copenhagen-based charging management platform supporting OCPP 2.0.1 and OCPI for multi-network operations
• Fuuse: UK charging management software provider focused on workplace and fleet charging with open protocol support

Investors

• Infracapital: invested in Connected Kerb, the UK's largest local authority EV charging provider
• BlackRock: major investor in European charging infrastructure through climate infrastructure funds
• Zouk Capital: manages the UK government-backed Charging Infrastructure Investment Fund

Action Checklist

• Specify CCS2 as the mandatory connector standard for all UK and European charging products
• Require OCPP 2.0.1 as a minimum in all charge point procurement and software development
• Implement multiple payment pathways including contactless, app-based, and Plug & Charge readiness
• Join interoperability testing programmes such as EV Roam and Open Charge Alliance conformance testing
• Design hardware architectures that accommodate future MCS upgrades for commercial vehicle applications
• Integrate with at least one roaming hub (Hubject or Gireve) and supplement with direct operator integrations for UK networks
• Publish real-time availability and pricing data through open APIs to comply with UK Public Charge Point Regulations

FAQ

Q: Should UK charging startups worry about NACS at all? A: Only if you plan to export products to North America or develop adapter accessories. For the UK and European markets, CCS2 is the mandated and universally adopted standard. No regulatory or market signal suggests NACS adoption in Europe. Focus product development resources on CCS2 optimisation, ISO 15118 integration, and OCPP 2.0.1 compliance.

Q: How much does it cost to achieve full interoperability compliance for a charging network? A: For a network of 100 to 500 DC fast chargers, achieving OCPP 2.0.1, OCPI, ISO 15118, and UK regulatory compliance typically requires £150,000 to £400,000 in software development and testing, plus ongoing certification and conformance testing costs of approximately £30,000 to £60,000 annually. These figures exclude hardware costs and assume a modern software architecture.

Q: When will Plug & Charge become mainstream in the UK? A: Based on current vehicle production timelines and charger upgrade cycles, Plug & Charge availability is expected to reach approximately 40 to 50% of UK public rapid chargers and 60 to 70% of new EVs by 2028. Full ecosystem maturity, where most sessions can use Plug & Charge, is unlikely before 2030. In the interim, contactless payment remains the most reliable universal payment method.

Q: Is OCPP 1.6 still acceptable for new installations? A: No. While OCPP 1.6 charge points will continue to operate, specifying 1.6 for new installations locks in known interoperability limitations and will require costly firmware upgrades or hardware replacement within 3 to 5 years. OCPP 2.0.1 should be the minimum specification for any new charge point procurement in 2026.

Sources

• OZEV. (2026). UK Public Charging Infrastructure: Annual Performance Report 2025. London: Office for Zero Emission Vehicles.
• CMA. (2024). Electric Vehicle Charging Market Study: Final Report. London: Competition and Markets Authority.
• DfT. (2026). Electric Vehicle Charging Statistics: January 2026. London: Department for Transport.
• ACEA. (2025). Electric Vehicle Charging Infrastructure in Europe: Status and Outlook. Brussels: European Automobile Manufacturers' Association.
• EV Roam. (2025). UK Charging Interoperability Testing Programme: Year 2 Results. London: EV Roam.
• ChargeUK. (2025). State of the UK Public Charging Network: 2025 Annual Report. London: ChargeUK.
• ChargeUK. (2026). OCPP Deployment Tracker Q1 2026. London: ChargeUK.
• CharIN. (2025). Megawatt Charging System: Global Deployment Status Update. Berlin: Charging Interface Initiative.
• BloombergNEF. (2025). Global EV Charging Infrastructure Outlook 2030. London: Bloomberg Finance LP.