WattEV Unveils 12 to 15 kV Solid-State Transformer for Megawatt Charging of Heavy-Duty Electric Trucks

WattEV, the California-based heavy-duty fleet charging operator already covered for its 370 Tesla Semi order (mgrid post 8256) and its 60-truck Forum Mobility partnership (mgrid post 8574), unveiled its own solid-state transformer (SST) on October 21, 2025. The product is a compact medium-voltage power conversion system rated for 12 kilovolt to 15 kilovolt utility input, designed to feed megawatt-class truck chargers without the lead times and weight of a conventional pad-mount distribution transformer.

The WattEV announcement is significant for two reasons. First, it is the first commercial-fleet operator to develop and brand its own SST, rather than purchase from an established power electronics vendor. Second, it directly addresses the single most constraining bottleneck in megawatt charging deployment: the multi-year backlog on conventional distribution transformers in the 1 MVA to 5 MVA class that megawatt charging requires.

WattEV positioned the SST as production-ready in 2026, with internal use at the company’s Long Beach and San Bernardino California truck-charging depots as the first deployments. The company has not disclosed the SST manufacturer of record, nor whether the design is a WattEV in-house architecture or a license of a third-party platform. WattEV is one of the few US companies that has shipped a commercial 1.2 megawatt Megawatt Charging System (MCS) on the open road, so the architectural design choices made by the company are now visible reference points for other fleet operators.

Megawatt-class chargers consume utility power at a current and harmonic profile that conventional 60 Hz distribution transformers handle poorly. IEEE Standard 519-2022 specifies harmonic distortion limits at the utility-customer interface; megawatt chargers without active filtering routinely exceed the standard. An SST converts incoming AC to a DC bus through a controlled converter, then synthesizes the high-current DC output to the charger’s power cabinet. The intermediate converter stage actively suppresses harmonic content, displacing the dedicated harmonic filter and the dedicated VAR compensator that a conventional iron-core architecture would require.

WattEV joins ABB E-mobility (MCS1200, launched April 2025) as one of the first companies to ship a megawatt-class fleet charging system with an integrated SST. ABB’s system uses ABB’s own February 2024 SST module; WattEV’s product positioning suggests a custom design. The two products will compete directly in the US heavy-duty fleet electrification market through 2026 and 2027.

Why It Matters

Fleet operators planning megawatt charger deployments in 2026 and 2027 should compare WattEV’s branded-SST approach against a multi-vendor procurement that buys an MCS charger and a separately specified medium-voltage transformer; the cost, lead-time, and serviceability tradeoffs deserve a side-by-side analysis before committing to a single-vendor stack. Utility account managers should treat WattEV’s in-house SST as evidence that fleet operators will increasingly push for direct medium-voltage service connections, which changes interconnection planning.

Critical Perspective

The WattEV SST announcement is a milestone for fleet-charging operators but should not be read as evidence that fleet operators will displace power-electronics vendors in the SST market. WattEV’s resources, even at its current scale, are dwarfed by Eaton, ABB, Hitachi, and the dedicated SST startups; in-house SST development is a strategic bet against a multi-vendor procurement strategy that most fleet operators of comparable size will not take. The company has not disclosed the power-electronics OEM partner producing the actual hardware, which matters because a fleet operator branding a vendor-built SST is a different proposition from a fleet operator developing original silicon-carbide topology. The 12 kV to 15 kV input range and MCS-spec DC output are necessary specifications rather than competitive differentiators; every commercial megawatt-charger SST in 2026 targets the same envelope. The Long Beach and San Bernardino depot deployments are useful operational pilots, but a sample size of two depots does not validate the SST architecture against the standard transformer-based alternative across diverse weather, utility tariff, and fleet duty-cycle conditions.

Related Coverage

• ABB E-mobility Launches MCS1200 1.2-Megawatt Charger With Integrated Solid-State Transformer for Heavy-Duty Trucks: direct competitor launches similar megawatt charger
• Eaton Closes Acquisition of Resilient Power Systems to Bring Medium-Voltage Solid-State Transformers In-House: competitor acquires solid-state transformer expertise
• Hitachi Energy Commits Additional $1.5 Billion for Transformer and Solid-State Transformer Capacity in Finland, Germany and North America: major player expands solid-state transformer capacity