CFLs are only energy saving when compared to the old incandescent light bulbs.
thats why theyre always labeled as 15w equiv to 60w, you would have needed an old 60w bulb to get the same amount light as the new 15w.
the cfls work pretty good for vegging plants with and thats where you can get some savings. instead of vegging for 6wks with a 400w HPS you run 100w of CFLs for 1/4 the cost
for flowering stick with HPS, lots more light per watt than with CFLs.
HPS are also hot so arent suited to a small box like CFLs are.