"George Patterson" wrote

Where do they get the electricity? I'd guess it's from something that
burns
fuel, but I could be wrong there.



Yep, the engines burn fuel to turn electrical generators.

It all comes back to efficiency. It is more efficient to make electricity,
and use it for the auxiliary needs of an airplane. Using bleed air to work
through an incredibly inefficient (and complex and heavy) system of
conditioning air is less efficient than generating electricity, and using
that energy to condition the air.

But you knew that, right? g
--
Jim in NC