Ground power and the APU: how parked aircraft use energy

Separate the aircraft’s needs

An aircraft at a stand still needs electrical power and cabin services. Its auxiliary power unit, or APU, is not the main propulsion engine. External electrical power can supply some ground needs, while pre-conditioned air provides another service. Plugging in electricity does not automatically describe every system or phase of a turnaround.

Distinguish the equipment

Fixed power at a stand, a mobile ground power unit and pre-conditioned air equipment have different functions. Schiphol describes fixed units, electric mobile units and electric cabin-air equipment in its airport programme. Their availability at one airport does not prove the same provision at every terminal or stand elsewhere.

Measure the right boundary

Replacing a diesel ground unit can reduce on-site exhaust, while the electricity still has a production footprint. Avoid confusing local air quality, airport-controlled emissions and an aircraft’s full flight emissions. A reduction in APU operation concerns a defined period on the ground; it does not turn the whole journey into a zero-emission flight.

Check operational compatibility

The equipment must be available and suitable, and airline procedures still apply. Charging infrastructure, servicing access and reliability influence deployment. For a useful comparison, state the period, equipment replaced, electricity basis and which emissions are included. Do not assign a universal saving to every parked aircraft.

SCSchiphol Airport