Well I just got done with my first indoor grow with a 400 watter. But my landlord got on my ass about the electric bill being high. I had a 400 watt hps and metal halide with 2 booster fans exhaust and intake and a high output oscillating fan. I wanted to do another grow with just 6 26watt cfls and two feminized autoflowers. I didn't know if it would be enough light for a good grow and keep the energy cost down.
I'd first wok on making the rest of your house energy efficient..changing to cfl or led lights throughout your house can drop the electiric bill a little giving you more room to work with. Also try to use large appliances less, such as ovens, clothes dryers or Air conditioning.....microwaves and hairdryers can use a ton too..but they don't run constantly so they're not as large of a concern. Use vertical lighting for the most efficiency. I'd run a 250w hps vertically and try to save electricity in other areas of the house to balance it out. 100+ watts worth of cfl in a dialed environment should get you plenty of quality smoke too.. the 20-30w cfls are actually more efficient then then larger cfls..(when talking corkscrews)