i wahs all but the most dirty (I have 3 under ) on 30 degrees and have always done so and just use regular washing powder. The only one which isn't particularly good at any temp is ecover, which is really sad as I wanted so much to use it.
However, if you are thinking that 30 won't kill the bugs, then you could just add a few teaspoons of napisan into the drawer with the powder as this will sanitise the wash as well as brightening whites and you still get to save energy.
Also, if you hang your towels and sheets on the line, the sun shine (when we get it ) and UV light in general kill bugs and bleach out marks and kill dustmite eggs. I do this as my son has dust mite allergy and then I just tumble them for a few minutes to fluff them up.
hope this helps.