Environmental impact: how modern GPUs & PCA reduce emissions compared to diesel GSE

What “APU-OFF” really means

An APU-OFF gate provides external electrical power (400 Hz) and pre-conditioned air, reliably and quickly,
so the APU can be shut down shortly after on-block and remain off until pushback readiness.

Why GPUs + PCA matter together

Power alone solves avionics, lighting and service loads, but cabin comfort and pack operation drive a big part of APU usage. PCA completes the system and improves compliance with APU-OFF procedures.

What changes vs diesel GSE

Replacing diesel equipment with fixed electric infrastructure typically reduces local air pollutants and noise,
and shifts CO₂ intensity to the electricity supply, enabling renewables, smart grids and energy management.

1) APU fuel burn at the stand

APUs are efficient for redundancy and autonomy, but on the ground they become a continuous fuel consumer. Many airline references show APU fuel consumption in the ~150-400+ kg/h band for broader fleets and conditions.

Converting fuel burn into CO₂ is straightforward: 1 kg of jet fuel ≈ 3.16 kg CO₂. That means even short APU runtimes, repeated across daily rotations, add up quickly in annual emissions reporting.

2) Diesel GPUs & diesel air units

Mobile diesel GPUs and diesel ACUs/PCA are often used where fixed infrastructure is limited. They reduce APU dependency, but still emit CO₂ and local pollutants directly at the gate.

For airports prioritizing local air quality and near-terminal noise reduction, fixed electric solutions typically offer the strongest “at-the-source” improvements.

3) Stand utilization & behavioral factors

APU-OFF success is not only about equipment. The biggest performance gap is often: how fast a stand is connected to ground power and air after on-block, and whether procedures are consistent across handlers and shifts.

Modern monitoring helps measure connection times, detect delays, and improve compliance, turning sustainability into an operational KPI.

Typical results airports target

• Lower CO₂ by minimizing APU runtime (and reducing diesel GSE runtime where replaced).
• Lower NOₓ and particulate matter directly at terminal-adjacent areas.
• Less noise at stands and in nearby communities.
• Faster, safer turnarounds (less cable congestion, fewer mobile units, cleaner apron zones).

Best-practice guidance for “aircraft on the ground” programs commonly highlights APU substitution with fixed ground power and PCA as a major lever, with significant reductions depending on utilization, stand coverage and procedures.

GPU: stable 400 Hz power

Solid-state 400 Hz systems provide clean power for avionics and ground servicing loads. When integrated as PIT, under-bridge or fixed converters, they reduce the need for mobile diesel units and simplify stand workflows.

Related ElectroAir solutions:
400 Hz frequency converters,
PIT systems,
under-bridge units.

PCA: the missing piece for true APU-OFF

In many climates, APU runtime is driven by cabin conditioning. PCA systems supply cooling/heating air externally, keeping passenger comfort and aircraft readiness while the APU stays off.

Related ElectroAir solutions:
EA-PCA under-bridge units,
air conditioning portfolio.

Digital layer: measure, enforce, improve

Emission reduction becomes repeatable when it’s measurable. Monitoring connection time to 400 Hz power and PCA
turns APU-OFF into a standard process rather than a “best effort” practice, improving compliance, reporting accuracy,
and stakeholder alignment.

1) Power backbone & capacity

Validate electrical capacity per gate and peak coincidence. Consider that PCA compressors can introduce transient loads, and that simultaneous aircraft + PCA demand shapes transformer, feeder and switchgear sizing.

2) Standardized interfaces

Choose consistent stand architecture: PIT vs under-bridge vs fixed cabinets. Standardization improves training, spares strategy, and reduces turnaround variability across stands.

3) Commissioning + training

Treat GPU/PCA as a system, not just products. Commissioning and training close the gap between “installed” and “used”. APU-OFF impact depends on consistent, confident operations.

4) SOPs & targets

Define measurable SOP targets: time-to-400Hz, time-to-PCA, acceptable exceptions (weather, tech), and responsibilities (handling agent vs terminal operator).

5) Monitoring & reporting

Track connection events and operating hours. Reporting can support ESG, regulatory programs, and internal “green gate” scorecards, turning sustainability into operational discipline.

6) Phased rollout strategy

Start with the highest-utilization stands, then expand. Many airports combine fixed infrastructure at contact gates with battery/diesel mobility for remote stands during transition.

Is fixed 400 Hz power enough to turn the APU off?

Not always. In many conditions the APU stays on for cabin conditioning. Adding PCA significantly increases APU-OFF compliance,
especially in hot summers, cold winters, and high passenger comfort requirements.

Do electric GPUs and PCA eliminate emissions completely?

They remove local tailpipe emissions at the stand. Overall CO₂ depends on the electricity carbon intensity,
which can improve over time through renewable sourcing, grid decarbonization and energy management.

What is the most common reason APU-OFF programs underperform?

Process gaps: delayed connection to 400 Hz/PCA, inconsistent SOPs across handlers, and lack of measurement.
Modern projects treat monitoring and training as part of the solution – not an afterthought.

Can this be rolled out in phases?

Yes. Many airports start with the highest-utilization contact stands and expand. Hybrid models (fixed infrastructure + mobile battery units) can maintain coverage while capex is staged.