Here is an exert from "See How It Flies," section 7.5.4:
2 exact same a/c at the same weight are flying at different altitudes but are both at the exact same AOA. At the higher altitude:
- the lift is the same (since lift= weight)
- the L/D ratio is the same (since it depends on AOA, and both are equal)
- the drag is the same (since L/D are the same)
- the thrust is the same (since thrust=drag)
- the IAS is the same (the produce the same lift at the same AOA)
- the TAS is greater (since the density is lower at higher altitudes)
- the power required is greater (since power= TAS*drag, as TAS is higher above).
So, any a/c requires more power required to maintain a given IAS or AOA at higher altitudes. Wind does not directly affect the power, but it does affect the groundspeed, which effects the total fuel burned (i.e. higher g/s= reach destination sooner, less fuel burned, even if this a/c is flying at the exact same power setting with the same fuel burn as an a/c with a low g/s).