Spoiler alert: Not true. Even at maximum load, high-quality VSD compressors – like those from Atlas Copco – are at least 2% more efficient than their fixed-speed equivalents. And in nearly every real-world scenario, the efficiency gap is significantly greater.
Fact: Very few compressors run at full load all the time
Only a small fraction of facilities operate with 100% constant air demand. If your compressor is running at maximum load around the clock, it’s likely undersized. In reality, most applications see air demand fluctuate throughout the day, week, or year.
In these conditions, a VSD compressor adjusts motor speed to match actual demand – delivering far more efficient operation than a fixed-speed machine, which runs at full motor capacity no matter what.
Fact: Not all VSD are created equal
Some VSD are little more than a fixed-speed compressor retrofitted with an inverter. This approach leads to inefficiencies, especially at higher loads, due to mismatched components and excess heat from gearboxes or drives not designed for dynamic operation.
Atlas Copco VSD are built from the ground up as integrated systems – with optimized (often dedicated) motors, inverters, and thermal management. That’s why even at full load, they outperform premium fixed-speed machines.
Fact: Proper sizing is critical to compressor efficiency
Running a compressor at 100% capacity continuously is a sign of poor sizing. Compressors should operate at around 80% of capacity for optimal efficiency and lifespan. Oversizing wastes energy; undersizing shortens equipment life and raises the risk of pressure drops.
Atlas Copco provides tools like SMARTLINK to track load profiles, helping you properly size and maintain your system to avoid performance and efficiency issues.
Fact: High-efficiency motors push VSD performance even further
Variable speed drive (VSD) technology enables the use of interior permanent magnet (iPM) motors, which deliver significantly higher efficiency compared to traditional asynchronous motors.
By combining a high-efficiency iPM motor with a direct-drive system, controlled by an advanced inverter and paired with an optimized compressor regulation system, the result is a VSD compressor that surpasses the performance of a fixed-speed compressor—even at full load conditions
Fact check summary
Claim: VSD compressors are less efficient than fixed-speed units at maximum load.
Verdict: False. Even under full-load conditions, integrated VSD systems are at least 2% more efficient – and they deliver significantly better performance under typical variable-load conditions.
