Currently, the majority of aircraft use their main engine while moving around on the ground. This can account for as much as 5% of the fuel that they use in their journey.
By running the taxiing on electricity, whether from batteries or a generator, either reduces the fuel burned by as much as 90% or more. This means that there is a saving of around 5% of fuel per flight.
With major airlines, the fuel used on a flight accounts for around 22% of the cost of the flight, which means that this 5% saving of fuel cuts overall costs by around 1%. In the cut-throat world of airlines, a 1% advantage over another airline can quickly become a significant issue. Put differently, it is thought, that each aircraft with an EGTS system installed will save around $250,000 a year. As such even an incredibly expensive EGTS system would quickly pay itself back and then some. It will also make airports far less noisy for much of the time.