That's not enough power to be worried about, as long as you pay your bills in a timely manner. My computer, which is on 24/7, eats 450 watts all by itself. A microwave or hair dryer eats more energy than a 1000 watt light. No need to get paranoid on account of that much electrical useage. I wouldn't go beyond two 1k lights though, unless it's a rental house and you aren't running much of anything else. And again, be sure your bills are paid promptly. That's probably THE most important thing, as delinquent payments immediately draw attention to you from the electric company.