You don't show the pertinent issue of the plotyy call you use but
hAx=plotyy(x, y1, x, [y2 y3]);
will put the first on the LH axes and the other to on the right. Of course, you don't need the temporary variables at all, either...
hAx=plotyy(sun.LocalTime,sun.PowerMW,[sun.PowerMW1,sun.PowerMW2]);
does the same thing with the original variables. Salt to suit re: "who's on first", etc., etc., as far as which quantities go where, of course...
ERRATUM Dang keyboard! Typed what I wrote instead of what I meant! :( I missed the second 'x' in the variable list, sorry. Corrected above (although I see you did find it, too).
