Explainer: Charging standards & interoperability (NACS, CCS) — what it is, why it matters, and how to evaluate options

In January 2025, the Society of Automotive Engineers officially published SAE J3400, codifying what was previously Tesla's proprietary North American Charging Standard (NACS) as a recognized industry connector. Within 12 months, every major automaker selling vehicles in North America announced plans to adopt the NACS connector, representing a shift that will affect over 35 million battery electric vehicles projected to be on US roads by 2030 (BloombergNEF, 2025). For sustainability professionals managing fleet electrification, workplace charging, or site development, understanding the evolving landscape of charging standards is no longer optional. The wrong infrastructure decision today can lock an organization into expensive retrofits or leave assets stranded as the market consolidates around new norms.

Why It Matters

The EV charging ecosystem in North America has operated under a fragmented standards landscape for over a decade. The Combined Charging System (CCS1, formally known as SAE J1772 Combo) has served as the dominant DC fast charging connector for non-Tesla vehicles since 2012, while Tesla built its proprietary Supercharger network using a smaller, lighter connector that carried both AC and DC power through a single port. This fragmentation created real costs for charging network operators, fleet managers, and site hosts who had to deploy multiple connector types, manage compatibility issues, and navigate a confusing user experience that slowed EV adoption.

The US Department of Energy estimated in 2024 that connector fragmentation added 15 to 22% to the total cost of public charging infrastructure deployment when accounting for dual-connector stations, adapter inventory, and increased maintenance complexity (DOE, 2024). The National Electric Vehicle Infrastructure (NEVI) Formula Program, which allocated $7.5 billion in federal funding for EV charging along highway corridors, initially required CCS1 connectors at all funded stations. In February 2024, the Federal Highway Administration updated NEVI minimum standards to also require at least one NACS connector per station, reflecting the industry's direction of travel.

For sustainability professionals, the implications extend beyond technical compatibility. Charging infrastructure represents a 10 to 20 year capital commitment. A Level 3 DC fast charging station costs $150,000 to $300,000 per unit installed, and charging networks represent multi-million dollar investments for fleet operators, commercial real estate developers, and municipalities. Selecting the right connector standard, communication protocol, and interoperability framework directly affects asset utilization, driver satisfaction, and long-term return on investment.

Key Concepts

Connector Standards: NACS vs. CCS1

The NACS connector (now SAE J3400) is physically smaller and lighter than CCS1, weighing approximately 1 pound versus 6 pounds for a typical CCS1 cable assembly. The NACS design integrates AC and DC charging into a single port, while CCS1 uses a combined connector that adds DC pins below the standard J1772 AC connector. NACS supports power delivery up to 1 MW (Megawatt Charging System specifications are still being finalized) and is rated for up to 1,000 V DC at 1,000 A in its current specification.

CCS1 has been the default DC fast charging standard for North American automakers since 2012. It supports power delivery up to 350 kW in current deployments, with Megawatt Charging System (MCS) extensions under development for heavy-duty vehicles. CCS2, a variant using the Type 2 AC connector, dominates in Europe and is mandated under the EU Alternative Fuels Infrastructure Regulation (AFIR).

CHAdeMO, the DC fast charging standard developed by Japanese automakers, has largely exited the North American market. Nissan, the last major CHAdeMO proponent in North America, confirmed in 2025 that all future Nissan and Infiniti EVs sold in the region will use NACS connectors. CHAdeMO retains significant market share in Japan and maintains relevance for bidirectional charging (vehicle-to-grid) applications where its protocol maturity exceeds both CCS and NACS.

Communication Protocols

Physical connectors are only one layer of interoperability. The communication between the vehicle and the charging station determines authentication, billing, power negotiation, and session management.

The Open Charge Point Protocol (OCPP), maintained by the Open Charge Alliance, is the dominant communication standard between charging stations and network management platforms. OCPP 2.0.1, released in 2020, supports advanced features including smart charging, local load management, ISO 15118 Plug-and-Charge, and improved security through certificate-based authentication. The US Joint Office of Energy and Transportation recommended OCPP 2.0.1 as the baseline protocol for all federally funded charging stations in its 2025 technical guidance (Joint Office, 2025).

ISO 15118, the Plug-and-Charge standard, enables automatic vehicle authentication and billing without RFID cards or mobile apps. The vehicle and charger exchange digital certificates through the charging cable, identifying the vehicle, authorizing the session, and routing payment automatically. Tesla has used a proprietary version of this concept since the Supercharger network launch, and ISO 15118 adoption is expanding across CCS and NACS networks as automakers integrate the standard into vehicle software.

The Adapter Question

During the transition period, adapters bridge the gap between legacy CCS1 vehicles and NACS infrastructure (and vice versa). Tesla began selling CCS1-to-NACS adapters in 2023, and several third-party manufacturers now offer adapters at $150 to $250 per unit. Adapters typically support power delivery up to 250 kW, though some models limit throughput to 150 kW due to thermal management constraints.

For fleet operators, adapter-based strategies introduce operational friction: adapters can be lost, stolen, or damaged; they add a failure point to the charging session; and they may not support all communication protocol features (particularly ISO 15118 Plug-and-Charge). Most fleet electrification consultants recommend treating adapters as a transitional measure with a 2 to 4 year useful life, not as a permanent infrastructure strategy.

What's Working

Tesla's Supercharger network expansion and NACS adoption has created the most reliable and widely available DC fast charging network in North America. As of Q4 2025, the Supercharger network comprised over 28,000 stalls across 3,200 locations in the US and Canada, with an average uptime exceeding 98%. The decision to open the Supercharger network to non-Tesla vehicles via the NACS connector began in earnest in mid-2024, and by early 2026, over 65% of Supercharger locations supported non-Tesla NACS vehicles (Tesla, 2026). This network effect has been a primary driver behind other automakers' decision to adopt NACS.

ChargePoint's dual-connector deployment strategy demonstrates how network operators are managing the transition. ChargePoint, which operates over 70,000 active ports in North America, announced in 2024 that all new DC fast charging installations would include both NACS and CCS1 connectors as standard. The company's modular hardware architecture allows existing CCS1 stations to add NACS connectors through a cable swap costing $3,000 to $8,000 per port, significantly less than full station replacement. By late 2025, ChargePoint reported that 40% of its DC fast charging portfolio had been upgraded to dual-connector capability (ChargePoint, 2025).

Electrify America's NEVI-funded corridor buildout shows how federal funding is accelerating standardization. Electrify America, the Volkswagen Group subsidiary that operates the second-largest DC fast charging network in the US, committed $2 billion to network expansion between 2024 and 2027. All new installations comply with updated NEVI requirements, featuring at least four 150 kW CCS1 ports and one NACS port per station. The company has also implemented OCPP 2.0.1 across its network, enabling third-party roaming agreements that allow drivers to use a single account across multiple charging networks (Electrify America, 2025).

What's Not Working

Interoperability between different charging networks remains inconsistent despite protocol standardization. A 2025 study by the National Renewable Energy Laboratory (NREL) tested 450 public charging sessions across 12 networks in 8 states and found that 17% of sessions experienced at least one interoperability failure, defined as inability to authenticate, initiate, or complete a charging session due to software or communication errors (NREL, 2025). The most common failure modes were RFID authentication timeout (38% of failures), payment processing errors (27%), and power delivery negotiation failures between vehicle and charger (22%).

Station reliability also varies dramatically by operator. The same NREL study found uptime rates ranging from 94% for Tesla Superchargers to as low as 72% for some smaller network operators. Broken screens, damaged cables, software errors, and network connectivity issues account for most downtime. The NEVI program requires a minimum 97% uptime for funded stations, but enforcement mechanisms remain limited, and many states lack the technical capacity to independently verify uptime claims.

Legacy CCS1 infrastructure faces an uncertain future. With every major automaker committed to NACS for new North American models by 2026 or 2027, the installed base of CCS1-only vehicles will peak around 2028 and then decline through natural fleet turnover. Charging network operators with large CCS1-only deployments face a strategic decision: retrofit with NACS connectors (at $3,000 to $8,000 per port), maintain CCS1 for the declining legacy fleet, or replace stations entirely. The economics favor dual-connector retrofits for high-utilization sites and potential decommissioning for low-utilization CCS1-only locations.

Key Players

Category	Organization	Role
Established	Tesla	Operates Supercharger network; developed NACS connector; opening network to non-Tesla EVs
Established	ChargePoint	Largest open network operator in North America; dual-connector deployment leader
Established	Electrify America	Second-largest US DC fast charging network; major NEVI funding recipient
Established	ABB E-mobility	Leading charging hardware manufacturer; supplies DC fast chargers globally
Established	Schneider Electric	Provides grid integration and energy management for charging infrastructure
Startup	FreeWire Technologies	Battery-integrated chargers reducing grid upgrade requirements
Startup	AmpUp	Cloud-based charging management platform for fleet and workplace charging
Startup	Nuvve	Vehicle-to-grid platform enabling bidirectional charging revenue
Investor	BlackRock Decarbonization Partners	Major infrastructure investor in EV charging networks
Investor	Energy Impact Partners	Venture fund focused on grid-edge and mobility electrification

Evaluation Framework for Sustainability Professionals

When evaluating charging infrastructure decisions, sustainability teams should assess five dimensions:

Connector futureproofing. For new installations in North America, NACS should be the primary connector, with CCS1 included for backward compatibility during the transition period. Budget for dual-connector capability at all DC fast charging sites commissioned before 2028.

Protocol compliance. Require OCPP 2.0.1 support in all new hardware procurement. Insist on ISO 15118 Plug-and-Charge capability, even if initial deployment uses RFID or app-based authentication, to preserve the option for frictionless charging as the vehicle fleet matures.

Grid integration readiness. Evaluate whether hardware supports bidirectional power flow, dynamic load management, and integration with building energy management systems. These features may not be needed today but will be essential as fleet sizes grow and utilities implement time-of-use rates and demand response programs.

Network interoperability. Ensure that charging hardware is not locked to a single network operator's platform. Open protocol support enables switching providers without hardware replacement and supports roaming agreements that maximize driver convenience.

Total cost of ownership. Model 10-year costs including hardware, installation, electricity, network fees, maintenance, and potential retrofit or replacement costs. The lowest upfront cost option frequently becomes the most expensive option over the asset's useful life.

Action Checklist

• Audit existing charging infrastructure for connector types, protocol versions, and network platform dependencies
• Develop a 3 to 5 year charging infrastructure roadmap aligned with fleet electrification timelines and employee EV adoption projections
• Specify NACS plus CCS1 dual-connector capability and OCPP 2.0.1 support in all new charging hardware RFPs
• Evaluate NEVI and state-level incentive eligibility for planned charging installations and ensure compliance with current technical requirements
• Establish uptime monitoring and reporting processes for all managed charging infrastructure, targeting 97% or higher availability
• Negotiate utility rate structures and demand charge management strategies before committing to high-power DC fast charging installations
• Create an adapter management policy for fleet vehicles during the CCS1-to-NACS transition period
• Engage with facilities and electrical engineering teams to assess site electrical capacity and plan grid upgrades for future charging expansion

FAQ

Q: Should I install NACS-only chargers or dual-connector stations? A: For new installations in 2026, dual-connector (NACS plus CCS1) is the recommended approach. The incremental cost of adding CCS1 capability to an NACS station is $3,000 to $8,000 per port, a modest premium that ensures compatibility with the approximately 4 million CCS1-equipped vehicles already on US roads. By 2029 or 2030, as the CCS1 fleet declines, NACS-only installations may become appropriate for new sites with low legacy vehicle traffic.

Q: How does NACS adoption affect workplace charging installations? A: Most workplace charging involves Level 2 (AC) stations, which use the J1772 connector that is physically compatible with NACS vehicles via the adapter included with every NACS-equipped non-Tesla vehicle. For Level 2 workplace charging, J1772 remains the universal standard and does not need to be replaced. For workplace DC fast charging (less common but growing for fleet applications), dual-connector NACS/CCS1 stations are recommended.

Q: What happens to my existing CCS1 charging infrastructure? A: Existing CCS1 infrastructure will remain usable for years. CCS1 vehicles will be manufactured through at least 2026, and the existing fleet will remain in service for 10 to 15 years beyond that. For high-utilization stations, retrofitting with NACS connectors makes economic sense now. For low-utilization stations, a watch-and-wait strategy may be appropriate, with retrofit decisions driven by observed changes in local vehicle mix. Avoid decommissioning functional CCS1 infrastructure prematurely, as the remaining CCS1 fleet still needs charging access.

Q: Is CHAdeMO still relevant for any use case? A: In North America, CHAdeMO relevance is limited to legacy Nissan Leaf and Mitsubishi Outlander PHEV owners and certain bidirectional charging (V2G) applications where CHAdeMO's mature bidirectional protocol provides functionality not yet widely available via CCS or NACS. New CHAdeMO infrastructure deployment in North America is not recommended. In Japan, CHAdeMO remains the primary DC fast charging standard and continues to evolve with higher power ratings.

Q: How do I ensure charging stations qualify for federal NEVI funding? A: NEVI-funded stations must meet Federal Highway Administration minimum standards, which as of 2025 require: location within 1 mile of a designated Alternative Fuel Corridor; at least four 150 kW DC fast charging ports with CCS1 connectors; at least one NACS connector; OCPP 2.0.1 support; minimum 97% uptime; payment acceptance via contactless credit/debit card; and pricing displayed per kWh. States administer NEVI funds through individual deployment plans, so specific requirements may vary. Consult the Joint Office of Energy and Transportation's technical assistance resources for current state-by-state guidance.

Sources

• BloombergNEF. (2025). Electric Vehicle Outlook 2025: North America Market Forecast. New York: Bloomberg Finance LP.
• US Department of Energy. (2024). National EV Charging Infrastructure Assessment: Costs, Gaps, and Deployment Strategies. Washington, DC: DOE Office of Energy Efficiency and Renewable Energy.
• Joint Office of Energy and Transportation. (2025). Technical Guidance for NEVI Formula Program: Charging Station Design and Interoperability Standards. Washington, DC: Joint Office.
• Tesla. (2026). Supercharger Network: 2025 Annual Performance and Expansion Report. Austin, TX: Tesla Inc.
• ChargePoint. (2025). Annual Infrastructure Report: Network Expansion and NACS Integration Progress. Campbell, CA: ChargePoint Holdings Inc.
• Electrify America. (2025). National Charging Network Update: NEVI Compliance and Deployment Milestones. Reston, VA: Electrify America LLC.
• National Renewable Energy Laboratory. (2025). EV Charging Interoperability and Reliability Assessment: Multi-Network Field Study. Golden, CO: NREL.
• SAE International. (2025). SAE J3400: North American Charging Standard (NACS) Connector Specification. Warrendale, PA: SAE.