Way too much!!!! I spend about $180 per month. I think it because of all the computers around here. We have about five running at all times.
I am also self employed so work from home as well which adds to the costs.
A few things to consider:
Next time you buy a computer, make sure it meets ENERGY STAR 4 standards, the latest energy efficiency standard, and better yet make sure it meets EPEAT Gold or at least Silver standard. I have an EPEAT Gold desktop computer that about as much electricity as a 40-watt light bulb, and a super-efficient EPEAT Gold monitor that adjusts its light output based on the ambient light in the room. None of those cost more than standard models and you save big bucks on electricity.
The other thing is that your computers shouldn't be running "at all times." Use the sleep function, it makes a huge difference. Even better, turn your computers and monitors off at night when you're not using them (unless one of them is a server, for example). In the old days you were advised that turning a computer on and off was bad for the electronics, but that hasn't been true since the early 1990s (a fact I confirmed with IBM, Dell, and Apple engineers more than a decade ago). I turn off my computers every night and have done so for years; it does no harm.
I work at home as well, and all my equipment is EPEAT Gold or Silver. We pay about $120/month for all electricty (which includes our heat and hot water) for a three-bedroom detached home.
One of the biggest electricity consumers in a house is typically a dryer. The other is a teenager.
When my teenage stepdaughter moved out last year, our electricity bill dropped by 40 percent, mainly because she always kept the heat cranked in her bedroom with the window open, never turned off lights, and washed her clothes and used the dryer constantly; she refused to use our clothesline.