The choice of standby and shut down is now complicated by a second question: hibernate or shut down. For environmental and technical reasons, there is one clear answer, and most opposing arguments don't hold much water.
Power Down Options
Windows users have three choices every time they walk away from their computers: standby, hibernate or shut down (Macs only offer sleep or shut down, but all the same principles apply). The simple choice: shut down. This saves power and is good for the computer.
Standby is like "nodding off" during class or a meeting. The computer keeps your applications running and documents open. Power is feeding to your computer memory, but peripherals are powered off and the hard drive power is minimized. The computer "wakes up" quickly from standby mode, and should look just like it did when you walked away.
The biggest drawback of standby mode is the power usage, and it should only be used when leaving the computer for a brief period.
Computing hibernation is more like a nap. It recalls all open documents and applications, but shuts down power to the computer. Again, the computer should look exactly as it did when you selected hibernate mode, but the computer takes longer to "wake up" from hibernate.
The hibernate mode uses no power, but it is still active enough to automatically restart and begin using power again in the middle of the night. A virus or scheduled tasks can cause this power-wasting function.
Here is a Microsoft summary of the two "sleep" options.
A full shut down is more like a full night's sleep or even biological hibernation. It powers off your computer completely. It's always the best option when you are not using your computer for a while.
It is the best environmental option because it draws no power, and can even safely unplug the computer or shut off the power strip to the computer and all the other office peripherals. The power savings are also financial savings.
In early 2009, USA Today said U.S. organizations waste $2.8 billion and 20 tons of carbon dioxide each year powering idle computers. The numbers are from the 2009 PC Energy Report from the 1E software company and the Alliance to Save Energy.
It is also the best bet for the computer's "health," as described in this guide to powering down Vista laptops.
Slow Down. What About ...?
To be sure, there are arguments against shutting down computers, but they aren't particularly convincing.
1. The extra startup and shut-down time is a waste of productivity: C'mon, few of us are truly productive every minute of the day. Switch on your machine before you get a cup of coffee or chat up the girl in the neighboring cube. If you can't wait five minutes in the morning, loosen up your schedule.
2. The computer needs to remain in standby for maintenance and updates: Schedule the updates for times during the workday when you are at lunch or on break.
3. I demand the convenience of a quick return from standby mode: See No. 1. Even if you can afford the added utility bill costs, the environment may not be able to.