The U.S. Department of Energy's states, "For energy savings and convenience, consider turning off the monitor if you aren't going to use your PC for more than 20 minutes; and both the CPU and monitor if you're not going to use your PC for more than two hours." Computer monitors account for a large portion of a computer’s energy use. To manage energy usage, turn monitors off when not in use.
Reducing your computer's power consumption can be a surprisingly easy way to save money, do a little something for the planet, and extend your equipment's life. Assuming that you shut down your computer for 16 hours a day (versus keeping it active 24-7), you could save $0.16 and 2.63 pounds of carbon dioxide per day, or 960 pounds per year. A car emits about 2,666 pounds of carbon dioxide per year, meaning that the energy you will save over the course of the computer’s life (3 years = 2,880 lbs) will equal a bit more than taking a car off the road for a year.
A computer and monitor turned on for 2 hours a day costs $1.44 per month. A computer and monitor turned on for 10 hours a day costs $7.20 per month. A computer running for 24 hours a day costs $17.28 per month. Do you REALLY need to use your computer for more than 2 hours a day? Try allotting an amount of time each day to check email, pursue money-saving scenarios, read blogs. etc. Then turn your computer OFF for the day. Not only will you save more than $15 a month, you'll get WAY more done around your house.
Furthermore, in the average home, 75 percent of electricity used to power electronics is consumed while the products are off. To save energy, simply plug your electronics into a power strip with an on/off button and turn them off when not in use.