I like to wash underwear and tights separately but it seems such a waste putting on a whole wash when I can only fill the machine half full (sometimes less).
I’ve had a look in the manual and my machine doesn’t have a half load unfortunately, but the quick washes are listed as only being able to half fill the machine. The problem is the quick washes say they are only for lightly soiled garments and the temperature only goes to about 30 or 40. 
I don’t think underwear would get properly clean on a wash for lightly soiled stuff on a low temp. So I don’t know whether to try using the light wash or if to just run the full wash just for half a load. It just seems such a waste of water/energy.
Any advice?