As everyone above said you need more light. What reason are you worried about the bill leaping? Money or stealth?
If its money then you will get back more bud the more light you have, my 600w costs me about 50-60 quid to run a month, Even if i only got one good ounce of bud from it i would still be saving money, 2 ounces i would be laughing in comparison to buying.
If its stealth then cut down on other things, Electric kettles use gas instead if you can, Use heaters a little less, change other bulbs in house to energy savers.
Fact is that to make decent bud you need to invest a little money.
All the best. Lots of good info on here so have a read or ask questions and everyone here will have growing like a pro.