EV Thermal Management Fluid Demand Exceeds 880 Million Liters By 2035

Like combustion vehicles, electric vehicles (EVs) require a suite of fluids to operate optimally. However, the quantities and properties of these fluids can be quite different. A strongly growing EV market presents a large opportunity for fluid suppliers, fluid additives, and fluid handling component suppliers.

The new IDTechEx report, “Thermal Management for Electric Vehicles 2025-2035: Materials, Markets, and Technologies,” predicts that over 880 million Liters of coolant fluids, combining water-glycol, oils, refrigerants, and immersion fluids, will be required for electric cars in 2035.

Where Is Each Fluid Used?

The drivetrain components (batteries, motors, and power electronics) should be kept in a certain operating temperature range for an EV to operate safely and efficiently. The cabin must also be kept at a comfortable temperature for the occupants.

Water ethylene glycol (WEG) typically forms the backbone of the thermal management system. In most cases, WEG is passed through the battery’s coolant channels or cold plates to keep the cells cool or warm them up in freezing conditions.

It is sometimes used to pass through a jacket around the motor and is typically fed through a heat sink to cool the inverter. It is also used to connect the thermal systems of the drivetrain components with the cabin.

The heat from these drivetrain components can often be transferred to the cabin’s thermal management system, reducing the need to heat the cabin air and improving efficiency separately. Due to its ubiquitous use, IDTechEx finds that WEG demand (in terms of volume) will be the largest EV fluid, with a sixfold growth in demand from 2023 to 2035.

Oils are commonly used to lubricate vehicle components like the gearbox and transmission. However, oil can also be used in an EV to cool motor components. As these oils are dielectric, they can direct contact with parts inside the motor, like the rotor and/or stator windings, improving thermal management and potentially reducing the size of the motor by removing the need for a water jacket around the stator.

Oil-cooling electric motors became the dominant motor thermal management strategy in 2022, with approximately 60% of new electric cars sold in 2023 using oil-cooled motors, according to IDTechEx’s research.

Refrigerant is essential to operating the air conditioning system for the occupant’s cabin. In some models, refrigerant is also used to cool the battery, which has challenges but can eliminate large portions of the WEG systems needed. This held a small market share in the early EV market, with the BMW i3 taking this approach, but it has seen a resurgence in recent years, with BYD adopting this technology for its e-Platform 3.0 vehicles.

Immersion cooling is an emerging thermal management strategy offering excellent thermal homogeneity. So far, it has been used only for high-performance certain off-road vehicles. While IDTechEx predicts growth for this technology, it does not expect it to be the dominant approach in the future.

What Is Changing With Each Fluid?

The fluid categories discussed are already a staple in combustion engine vehicles, but EVs present new demands.

It is common to see WEG products somewhat unchanged between combustion engine vehicles and EVs. However, there has started to be an interest in using low electrical conductivity (<100µS/cm) coolants with early adoption from players such as BYD and Hyundai. This adds an extra level of safety in the case of fluid leaks around electrical components like the battery.

To aid in system simplicity, a single oil that can lubricate gears and cool the motor is required. This challenges chemical compatibility with copper found in the motor windings, a material that would not have been a focus in a combustion engine’s oil.

The key trade-off to be made here is between thermal performance and mechanical properties. Generally, higher viscosities are better for lubrication but poorer for heat transfer. For this reason, fluid suppliers are trying to find a middle ground where viscosity is lower than would have been used in a traditional axle oil to aid in heat transfer but still high enough to keep the transmission’s wear to a minimum.

Refrigerants remain similar between combustion engine vehicles and EVs. The transition here is for the automotive industry as a whole. R134a was the standard, but in Europe, due to its high global warming potential (GWP), it was replaced with R1234yf in all vehicles from 2017 onwards, with other regions following suit.

The next big shift is likely from considering PFAS (per- and polyfluoroalkyl substances). Although there is no clear regulation or timeline enforcing R1234yf replacement, this hasn’t stopped the development of alternative refrigerants and their associated thermal management components.

VW deployed R744-based heat pump systems in certain ID models, and other thermal system suppliers like Hanon Systems have presented both R744 and R290 heat pump systems for EVs.

IDTechEx discusses EV refrigerants further in its “Thermal Management for Electric Vehicles 2025-2035: Materials, Markets, and Technologies” report. It also takes a deep dive into PFAS compounds and their replacements in its ” Per—and Polyfluoroalkyl Substances (PFAS) 2024: Emerging Applications, Alternatives, Regulations” report.

Increasing Demand Per Vehicle

While EV design trends like cell-to-pack and more integrated thermal management modules can decrease fluid intensity per vehicle, a few key trends, on average, are increasing the fluid volume required per vehicle.

This includes expanding battery capacities, more cars with dual motor options, growing adoption of oil-cooled motors, and further adoption of heat pump systems. Combining this with an increased EV demand, IDTechEx predicts that over 880 million Liters of coolant fluids will be required for electric cars in 2035.

The new IDTechEx report, “Thermal Management for Electric Vehicles 2025-2035: Materials, Markets, and Technologies,” examines the thermal management of the battery, motors, power electronics, and cabin and provides a deep dive into strategies, components, materials, market shares, and forecasts to 2035.