It's going to vary greatly anyway. I could mention that I got my first bill after folding almost 24/7 last month on my sig rig (at the time on a 750TX) and that my bill went up $10 for a total of about $76.00, but that wouldn't do you any good because energy costs in your area may be wholly different. When I lived a couple of towns over a few years ago with my best friend, our monthly electric bill was upwards of $100/mo, and we didn't have central air like I do at my current place, and I wasn't running a PC like I am now.