Challenges and Opportunities of Electrifying Off-Highway Machines

Manufacturers are increasingly exploring the use of electronic components in hydraulic systems, enabling more advanced control and resulting in higher efficiency and better system response.

April 22, 2025

Zifan Liu

The switch to electric off-highway vehicles can help reduce the need for hydraulic components that result in parasitic losses. (Bosch Rexroth)

The off-highway machine industry is embracing new technologies to optimize operations, specifically regarding electric and hybrid off-highway equipment. The electric off-highway equipment market is poised for growth, with an expected 12.5% compound annual growth rate (CAGR) from 2025-2034, reaching over $17 billion, according to Market Research Future .

Zifan Liu, Ph.D., Bosch Rexroth senior electrified systems engineer. (Bosch Rexroth)

These off-highway vehicles operate on tough terrain and require unprecedented amounts of power for long duty cycles. Diesel engines have always been the conventional application for this kind of work, but now hybrid and electric vehicles are starting to gain traction thanks to new innovations and more investment. While the implications of replacing traditional combustion engines with hybrid or electric counterparts can be intimidating, learning the challenges and opportunities each option holds gives end users the power to determine what’s right for their needs.

A major goal in switching to electric off-highway vehicles is to eliminate tailpipe emissions and boost energy efficiency by removing diesel engines, which still see less than 50% optimized efficiency. These engines are a major source of greenhouse gas (GHG) emissions, and with tougher environmental rules from recent years, there is more focus on implementing energy-efficient solutions before completely overhauling off-highway machines.

Rexroth’s eLion portfolio includes motors (96V EML1 shown), inverters, gearboxes, onboard chargers and more. (Bosch Rexroth)

Switching to electric off-highway vehicles doesn’t just cut GHG emissions through the elimination of diesel engines. The switch can also help reduce the need for hydraulic components to make more efficient machines that eliminate parasitic losses from valve throttling, for example. It also reduces the environmental impact associated with their production, disposal and potential leakage.

According to a 2023 study published in the Journal of Mechatronics and Artificial Intelligence in Engineering, moving elements such as the hydraulic motor, pump, control valve and cylinder decrease system efficiency due to leakage and friction losses. Additionally, electric off-highway vehicles are more efficient overall, need less maintenance and improve energy conversion, leading to lower operational costs and a smaller carbon footprint.

Challenges and opportunities

Rexroth engineered its electrohydraulic eOC pump to ensure the swash plate has the necessary over-centering capability, which is critical to enable negative displacement when boom regeneration occurs. (Bosch Rexroth)

There are challenges to keep in mind with electric off-highway vehicles. An overhaul of a machine’s power system requires careful consideration and comprehensive analysis. The batteries needed to electrify heavy equipment can incur an upfront cost that has not changed significantly over the years. For heavy-duty machines, these battery packs are expensive due to their large size compared to other components.

Lithium-ion batteries that power electric off-highway machines have their own limitations, especially when it comes to duty cycles. Most operators need a machine that can withstand long shifts – usually 10 to 12 hours. That requires massive batteries that still remain limited in power.

While electric batteries have higher upfront costs, the total cost of ownership (TCO) of electrified off-highway vehicles is favorable. End users can save money through the energy efficiency offered with electric systems alongside the lower maintenance costs from fewer moving parts. The cost of powering an electric off-highway vehicle compared to a conventional diesel engine vehicle is an important factor in determining total expense. While diesel fuel is expensive and subject to price fluctuations, electricity remains significantly cheaper.

Additionally, planning and integration are important when it comes time to deploy electric off-highway vehicles. Operators need to plan vehicle charging times and charging sources. This might mean adjusting shift times and determining the best solution, such as using an onboard charger (OBC). If these are deal breakers for operators, then a hybrid configuration may be the next best alternative.

Hybridization an alternative

Rexroth’s RM valve features a patented compensator-less design coupled with advanced control software to facilitate reverse flow when the boom is lowered during regeneration. (Bosch Rexroth)

Energy and operational efficiency are top priorities to ensure success. Hybrid systems – internal combustion engines with electric motors that drive hydraulic pumps – can also reduce vehicles’ total emissions without compromising their output. Typical hybrid configurations feature energy storage systems (ESS) that help balance efficient performance and sustainability while also extending the operational time.

In this case, the ESS functions as both a power and energy buffer. As a power buffer, it supports the system during peak load demands, enabling a smaller engine and optimizing engine efficiency. As an energy buffer, it allows the vehicle to operate in electric vehicle (EV) mode using the ESS alone. In both modes, the ESS contributes to reducing GHG emissions and increasing system efficiency. However, managing the various energy sources onboard presents a challenge, as it requires supervisory control at the vehicle level.

In some applications, the ESS is absent. In these cases, the main benefits come from the electrification of certain functions such as traction and power take-off (PTO), which eliminates the need for hydraulic components. However, the DC link control becomes challenging, particularly in terms of voltage stability and other factors.

Emerging trends

Off-highway vehicles with electrified systems can capture and regenerate energy for some processes, such as when a vehicle’s boom is down and the vehicle is braking. This requires valve and pump designs to change in order to enable precise energy regeneration.

For example, in a recent electric Compact Track Loader (eCTL) prototype developed by Bosch Rexroth using its electronic Open Circuit (eOC) axial piston pump, engineers needed to adapt its internal components and related control software to ensure the swash plate has the necessary over-centering capability. This is critical to enable negative displacement when boom regeneration occurs. Additionally, Rexroth’s RM valve features a patented compensator-less design, coupled with advanced control software, to facilitate reverse flow when the boom is lowered during regeneration.

Manufacturers are increasingly exploring the use of electronic components in hydraulic systems, enabling more advanced control and resulting in higher efficiency and better system response. In some applications, manufacturers are even considering fully electrifying the boom and bucket with battery-powered linear actuators that capture kinetic energy during vertical displacement.

Smarter data from AI and advancements in 5G connectivity and the IoT have helped tackle these challenges, especially in industries such as forestry that operate in remote locations. Machines with IoT tech and comprehensive telematics systems will positively impact electric off-highway vehicles in the coming years.

These solutions can help end users who are experiencing a lack of skilled operators, as real-time connections to information improve minute-by-minute operations, thus simplifying operations. With advanced, connected machines, operators have full access to monitoring, and an integrated display can provide a less complex way to operate a vehicle. These displays often include fewer buttons, voice control and a sleek design, making systems easier to use after some training.

There isn’t a consensus among industry experts on one option being fundamentally and unequivocally better than another – each has its own benefits and drawbacks. Moving forward, it’s important for operators to think about their use cases and what makes the most sense for them regarding operational efficiency.

Zifan Liu, Ph.D., Bosch Rexroth senior electrified systems engineer, wrote this article for SAE Media.