Here are some numbers to kick around (Jan '07 publication):
Cost (assumed fuel price of $3.10/gal)
1. Is it more expensive to run the APU than ground power?
Yes, it is more expensive to run the APU at all domestic stations and at many international stations. The cost to run an APU ranges from $128 - $314 per hour depending on the type of aircraft. The cost to run ground power is about $10 per hour and the cost to run air conditioning is about $12 per hour for a total of $22 per hour for gate power and air. Annually it costs about $1.3M per minute to run the APU system-wide. With increased fuel cost, Delta spends about $80M annually on APU usage .
2. When does it become less costly to operate an engine versus starting up the APU?
The times in the table below represent the approximate break-even point at which it becomes less costly to operate the engine versus starting up the APU. This is largely due to the financial charging structure of current maintenance service agreements, i.e. power by the hour, that cover many of Delta’s aircraft engines and APUs.
Aircraft Type Break-Even Minutes
MD-88 B777 2
B767-300, B767-300ER, B767-400ER 2
B737-700/800, B757 2
3. How much does it cost to purchase mobile equipment (ground power, air conditioning and heater)?
Mobile ground power units are generally about $35-40k, mobile air conditioning units are about $100k and mobile heaters are about $25-30k.
4. How much does it cost to move GSE to another station?
It can cost up to $5k per move for truck rental.