A typical aircraft APU burns between 100 and 300 kilograms (roughly 200 to 660 pounds) of jet fuel per hour, depending on the size of the aircraft and how much electrical and air conditioning load it’s handling. Smaller narrowbody jets sit at the lower end of that range, while large widebody aircraft push toward the upper end.
What an APU Actually Does
The auxiliary power unit is a small turbine engine, usually tucked into the tail of the aircraft, that generates electricity and supplies compressed air. When the plane is parked at the gate with its main engines off, the APU keeps the lights on, runs the air conditioning packs, and provides the pneumatic power needed to start the main engines. It can also run in flight as a backup if an engine or generator fails.
Because the APU is doing real work (compressing air, spinning generators), its fuel burn changes significantly based on what systems are drawing from it. Running the air conditioning packs is the biggest variable.
Narrowbody and Regional Jets
For a single-aisle aircraft like an Airbus A319, the APU burns roughly 200 kilograms (about 440 pounds) of fuel per hour on the ground. This figure comes from the GTCP85-series APU commonly installed on that family. Smaller regional jets with lighter APU models generally fall below that, though exact published figures are harder to pin down. The Embraer E-Jet family, for instance, uses a Hamilton Sundstrand APS 2300 unit that typically logs about 0.8 APU hours for every flight hour, suggesting airlines keep ground run times relatively short to control costs.
Widebody Aircraft
Larger aircraft burn noticeably more. Boeing 777 documentation states that the APU needs a minimum of 950 pounds (430 kilograms) of fuel available to start and run for the first hour. After that initial hour, steady-state consumption drops to about 675 pounds (306 kilograms) per hour. The higher first-hour figure accounts for the energy spike during startup.
Airbus A330 data breaks it down further by load. On the ground with air conditioning packs running, the APU burns about 215 kilograms per hour. Turn the packs off and it drops to around 140 kilograms per hour. That 75-kilogram difference illustrates just how much energy the cabin cooling and pressurization system demands.
APU Use in Flight
APUs aren’t just ground equipment. They can run at altitude, and the thinner air at cruise actually reduces fuel burn. On the A330, the APU consumes about 130 kilograms per hour at 20,000 feet with packs on, dropping to roughly 55 to 65 kilograms per hour above 30,000 feet without packs. These in-flight scenarios typically happen during engine-out situations, where the APU picks up electrical generation duties. At lower altitudes on a heavy aircraft, that figure can climb back up to 270 kilograms per hour because the denser air creates more drag on the APU’s inlet door and the unit works harder.
For flight planning purposes, crews often use a conservative estimate of around 250 kilograms per hour to make sure they carry enough reserve fuel if the APU needs to run during a diversion or single-engine approach.
Why Airlines Avoid Running It
At 200 or more kilograms of jet fuel per hour, APU operation adds up fast. A widebody aircraft sitting at the gate for two hours with the APU running can burn over 600 kilograms of fuel before it even pushes back. That’s fuel the plane then has to carry less of for the flight, or fuel that adds directly to operating costs.
This is the main reason airports invest in ground power units (GPUs) and preconditioned air systems built into the gate. Plugging into the terminal’s electrical grid costs a fraction of burning jet fuel. One cost analysis comparing the two approaches for an A319-class aircraft found that airport-supplied 400 Hz electrical power ran about 180 yuan per hour (roughly $25), while the APU’s fuel cost alone was several times higher. Multiply that across hundreds of gates and thousands of daily turnarounds, and the savings become enormous.
Many airports now mandate that airlines use ground power when it’s available, limiting APU run time to a few minutes before departure. Some impose fines for extended APU use, both for cost reasons and because of noise and air quality around the terminal.
Quick Reference by Aircraft Size
- Regional jets (E-Jets, CRJs): roughly 100 to 150 kg/hr on the ground
- Narrowbody (A319/A320, 737): roughly 150 to 200 kg/hr on the ground
- Widebody (A330, 777, A380): roughly 200 to 300+ kg/hr on the ground, varying with load
These are ground figures with typical electrical and air conditioning loads. In-flight figures are lower at cruise altitude and higher at low altitude under heavy load. The single biggest factor in all cases is whether the air conditioning packs are running off the APU or handled by another source.