What Is the Megawatt Charging System (MCS) for Electric Semi Trucks?

The Megawatt Charging System is a conductive DC fast-charging standard developed for heavy-duty electric trucks, buses and off-highway equipment, targeting charge rates above 1 megawatt on a single connector. Per CharIN's own MCS technology page, the system specifies a maximum of 1,250 volts DC and up to 3,000 amps DC, well beyond what any CCS1 connector on the market today is rated to carry.

The core connector, inlet and cable-assembly specification reached formal publication as IEC TS 63379 on February 9, 2026, issued by the International Electrotechnical Commission with CharIN e.V. members contributing the technical work. CharIN describes this publication as a landmark for MCS standardization, and it defines the physical hardware -- the pin, the housing, the mating cable -- that a truck and a charger both plug into.

MCS raises the ceiling on both voltage and current well past what CCS1 equipment is built for, which is why it needs its own connector rather than a faster version of the existing one. Today's CCS1 DC fast charging for medium- and heavy-duty trucks tops out at 350 kW in commercial deployment, per class-8-truck-charging-depot.json's own review of settled equipment -- MCS targets multiples of that on a single port.

The practical consequence for a depot is that MCS is not a software update to existing DC fast equipment. It is a different connector, different cable cooling requirements at that current, and in most cases a different service-level electrical connection, which is why a site planning for MCS has to design the pad, conduit and service headroom for it years before the hardware itself is buyable.

No. Publishing a connector specification is not the same as a vendor shipping a listed, service-supported charger built to it, and as of this September 2026 check, MCS equipment has not reached that stage. IEC TS 63379 standardizes the physical connector, inlet and cable assembly -- the part that lets different manufacturers' trucks and chargers physically mate -- which is a precondition for a competitive hardware market, not the market itself.

A fleet manager evaluating a depot today should treat MCS the way class-8-truck-charging-depot.json already frames it: settled equipment is CCS1 at 350 kW and below, from multiple vendors with service contracts behind it; MCS is a published standard without that vendor ecosystem yet. Anyone presenting MCS hardware as specifiable and buyable on a normal construction schedule in 2026 is ahead of what the standard's own publication history supports.

Electric Island, a public heavy-duty charging site in Portland, Oregon built by Daimler Trucks North America and Portland General Electric, opened April 21, 2021 with charging levels reported at over 1 megawatt per unit and the site wired for 5 megawatts of total capacity, per Portland General Electric's own investor-relations press release. This deployment predates both IEC TS 63379 (published 2026) and SAE J3271's Technical Information Report (published 2025), so it should not be described as an MCS-standard site -- it demonstrates that megawatt-class power delivery to a truck yard is achievable years ahead of the connector these two bodies have since standardized, not that it used that connector.

That distinction matters for a fleet manager: a site can be built with the electrical service, transformer and conduit sized for megawatt-class charging today, using whatever DC fast equipment is currently buyable, and swap in MCS-standard dispensers once a vendor ships them -- which is the approach class-8-truck-charging-depot.json recommends for any duty cycle that genuinely needs megawatt power.

SAE J3271 is a companion technical documentation effort covering the broader MCS system, published as a Technical Information Report in March 2025, organized into five subtopics: the electromechanical coupler, communication and controls, cable handling and cooling, use cases including bidirectional power transfer, and interoperability test procedures. Per SAE's own standards catalogue, these five subtopics were compiled into one initial document, with more detailed recommended-practice-level standards expected to follow.

Read together, IEC TS 63379 standardizes the physical connector hardware and SAE J3271 documents the surrounding system -- communications, cooling, testing -- that a working charger and truck both need to implement. Neither publication is itself a product; both are the groundwork a hardware vendor builds a certifiable, sellable unit against.

Build the passive infrastructure now and defer the powered equipment, which is the same pattern this site's own depot-design guidance already recommends for any capacity a fleet does not need on day one. Size the pad, the conduit runs and the service headroom for megawatt-class delivery if a duty cycle genuinely calls for it -- a long-haul Class 8 relay point rather than a return-to-base yard -- and populate the dispensers with buyable CCS1 equipment in the meantime.

For most fleets this question does not apply at all: return-to-base operations with an overnight dwell window rarely need megawatt-class power, because a long dwell converts a large power requirement into a modest one, as the route-feasibility and depot-sizing guidance elsewhere on this site works through in detail. Reserve MCS planning for the duty cycles that actually fail that arithmetic.