What is the harmonic content of a PWM signal?
If you have 50:50 mark space ratio you are dealing with a square wave and this should be a good start (this is for a 1kHz square wave): - 



When it comes to other duty cycles try this for size: -



Presumably your filter might be a 2nd order low-pass type made from L and C. Keep the resonant point at least 50% above 60Hz to prevent catestrophic series resonance at 60Hz. You can easily simulate this to see what current this filter might be taking an an unloaded 60Hz supply and I would recommend simulation to furnish you with the total harmonic distortion.