The main PC in our home used to be left on 24-7. After realizing the power consumption of doing such a thing was wasting a lot of electricity, I started putting all computers into sleep mode. This helped significantly but still, our family uses computers a lot, probably 5-12 hours a day and even more in the summertime and on weekends.
Using an 80+ Gold power supply and more energy efficient components in my PC, I managed to get the idle power consumption of the PC from 105 watts down to about 42 watts.
To my surprise, the seemingly efficient 4-year old, 24" LCD monitor was drawing about 75 watts on its own.
At 6-hours a day, the monitor uses about 164KWh of electricity/year or about $18/year (assuming 11 cents/ kWh electricity).
Recently LED monitors have come down in price. I have been eyeing a particularly awesome 23" LED monitor from Asus that runs $169 after main-in rebate. It only draws about 20 watts too. That works out to 44 kWh or only $4.82 in electricity/year, a savings of $13.26/year. After 6 years it would save almost $80 in electricity.
It seems frivolous to buy a new monitor when the current one works perfectly fine. But these LED ones are so awesome and super efficient. I must find a way to justify buying one!
If I sell the old monitor for $100. That along with the long term electricity savings more than covers the cost buying the new monitor.
Cha-Ching!