This may cost you a little bit initially, but over time you can save that money plus some. Check with your utility company, as some will give you some for free for asking and some have rebate programs where they give you money back for purchasing them. Also, keep your eyes our for coupons or rebates for CFL light bulbs, they do exist.
And since summer if fair time, your utility company (or some other one) might be passing them out. Keep your eye out for those fair freebies!