How to reduce the power used by PC ?

Many of people today face the ever increasing fact that electricity is getting more a more expensive. Computers tend to add a considerable amount to the bill as they sometimes run for long periods of time. But recently with the whole scare of global warming and what-not computer hardware manufactures have come around to the fact that more and more people want to become environmentally friendly and reduce the'r carbon footprint. So this is a great situation for the end user as the power bill is reduced and in turn, less pollution is made for the environment.

If you're thinking of building a new PC and want to reduce your power bill, consider the following points:

Buy a power supply unit that is 80 plus certified. This means maximum efficiency is obtained when your pc is running with minimum power wastage. PSU manufacture Cooler Master produces excellent power supplies that are 80 plus certified.
Consider purchasing a case that has excellent natural airflow. The more freely air can be moved, the less need for more case fans. Antec have advanced chassis that are aimed for low airflow situations.
Think about buying an energy efficient motherboard. Gigabyte have a lot to offer with their motherboards consisting of dynamic energy saving technologies, your PC will run much cooler and be more reliable.
The processor you purchase will make a big difference on power usage. Both Intel and AMD have technologies to keep power down to a minimum such as "green" CPU's. Intel processors currently are a lot faster but run hotter than AMD and AMD is a better value for money. You should also decide whether to buy either a dual core, quad core or six core.
Consider buy a Western Digital hard disk, as Western Digital has produced a "Green Drive" which is a technology that reduces hard disk power consumption.
When it comes to RAM, if you're not into gaming then you can get "Eco Friendly" RAM which used less power. It may run a little bit slower than normal RAM but if you're not into serious performance gaming or HD encoding then it's fine.
Some Graphics cards are Eco editions; you can take a look at them if you intend to do gaming every now and then or want to watch HD movies.

If you're not planning on building a PC anytime soon and would like to reduce power consumption on your existing system, try these ideas:

1) If you're running an AMD processor, enable Cool "n" Quiet in the BIOS as this will throttle the CPU when not in use.
2) If you're running an Intel processor, enable Intel SpeedStep Technology in the BIOS as this will throttle the CPU when not in use.
3) Lower your monitor's brightness setting.
4) Shut off your monitor in between breaks.
5) Don't leave your computer on overnight.

By following these points, you will see a reduction in power usage from your PC. This in turn means the air will be cleaner and you'll save money from your power bill.