If you (or your parents) are worried about electricity costs - you could always make an argument to save up a bit more money and purchase an LED system. Marineland's "Double-bright" strips are pretty expensive off the start (the size for your 55g would probably cost you $120 - $150) but they consume next to zero electricity and can still grow great plants.
I have one on top of my 26gal and it grows Anacharis, Java Fern, Corkscrew Val, Wisteria and Anubias Nana just fine for only 6.2watts.