It works best when you have soft water but I have found that Joy soap mixed with a tad of amonia on a dish rag works wonders for outside windows.  They actually sparkle better.  I always wear gloves.

Then if you dont worry about water spots (some areas have better water) you can hose the windows and they dry beautifully.  If you have hard water with lots of calcium then a Squeegee after rinsing will leave them

lovely.  It is also great because you can use more muscle than with a ordinary paper towel.  To really cut down on expense in doors you can use newspapers- be careful not to let the ink get too wet.  Amoneia works great also on tile

floors and so inexpensive compared to other cleaners- make sure it is soap free and it will not leave a residue.  You may need to leave a window cracked if you use much of it until it dries.