Peak power density of EV motors up 45% since 2019, RWTH Aachen study finds

Electric motor peak power density rose from 1.68 kW/kg in 2019 to an average of 2.43 kW/kg for 2024–2025 models — a gain of nearly 45 per cent — according to a benchmarking study by the Chair of Production Engineering of E-Mobility Components (PEM) at RWTH Aachen University, published in the specialist journal Energies.

The study, titled Review and Benchmarking of Electric Motor Product Design and Manufacturing Technologies from the Chinese Market, examined electric motors from vehicles of model years 2019 to 2025. It centred on the Chinese market and was supplemented by comparative data on European and US drivetrains. For production planners and purchasing teams, the headline finding is reassuring: the three markets differ little in fundamental architecture.

That convergence covers housing structures, rotor and stator geometries, and the cooling concepts of newer models. The pronounced differences sit in materials and individual components — precisely the areas that affect sourcing decisions and tooling.

Where the markets actually diverge

Chinese manufacturers increasingly use magnesium alloys for motor housings, while European manufacturers more frequently opt for aluminium. The study also identifies a split in power distribution busbars (the conductive bars that carry current between components):

• Chinese manufacturers predominantly use powder-coated busbar solutions.
• European manufacturers tend to employ more complex assemblies, embedding multiple copper bars in a polymer component.

What does this change for European suppliers? It signals that competing with Chinese drivetrain makers on cost and weight is less about a different technology race and more about material and process choices — magnesium housings and simpler busbar designs are levers worth evaluating.

Speed is the power-density lever

Across all three markets, the study identifies a clear trend toward more compact, highly integrated drivetrain units. Since 2022, highly integrated concepts — where motor, transmission and power electronics are combined more closely — have dominated the examined sample.

The main driver behind the power-density gain is higher rotational speed. Between 2020 and 2022, maximum motor speeds clustered between 8,000 and 17,000 rpm. Newer drivetrains increasingly operate at 20,000 rpm or higher, with some motors reaching up to 30,500 rpm. In parallel, the average gear ratio rose by around 21.5 per cent over the period examined.

Higher speeds allow smaller rotor and stator diameters, which cuts material usage. The researchers caution, however, that higher speeds do not automatically produce more compact motors — in some cases, manufacturers use them to raise achievable vehicle speed instead.

Cooling shifts raise manufacturing demands

Cooling systems are also shifting. Older motors relied predominantly on classic water jackets, while newer drivetrains increasingly combine direct oil cooling for both the rotor and stator. The study notes this places higher demands on sealing and component manufacturing — a direct call on process engineering and quality control for Tier 1 suppliers (companies supplying OEMs directly).

The study's overall verdict: China is an important driver for electric drivetrains, but no fundamentally different technical direction has emerged compared with Europe or the USA. The differences lie in specific implementation and material choices, not in a divergent architectural path.

For manufacturing practitioners, the near-term items to watch are the pace of oil-cooling adoption and its sealing requirements, whether magnesium housings spread beyond Chinese plants, and whether average motor speeds push past the 30,000 rpm mark in the next model cycle.