Sleep Mode

Sleep mode, also known as “suspend” or “stand by” is a low-power mode for computers and other electronic devices. When in sleep mode, power is cut to all non-essential computer functions. It is a good idea to put your computer in sleep mode when you won’t be using it for a while, but it would be inconvenient to shut it down and start it back up again (a good estimate is an absence of two hours or less).

  • To enter sleep mode in Windows 10, go to Start > Power > Sleep.
  • To enter sleep mode in Mac OS X, go to Apple > Sleep.

Computer Power Settings

It’s possible to conserve energy by configuring your computer to shut off its display, go to sleep, or shut down after being inactive for a certain amount of time. You can do this by changing the power settings. The Department of Energy recommends that you shut off your monitor when you won’t be using it for 20 minutes and your computer when you won’t be using it for 2 hours.

Luther’s lab computers are set to shut off their monitors after 20 minutes and to shut down after 180 minutes of inactivity. When no one is logged in to the lab computers, they go to standby mode after 10 minutes of inactivity. This is a 95 percent power savings as compared to being left idle. The 180 minute timeframe was chosen to go well past the length that classes are in session to prevent disruption to the class and the faculty.

Faculty and staff computers shut off their monitors after 10 minutes, lock after 25 minutes, and the computers go into sleep mode after 2 hours; after 4 hours they hibernate.


Phantom Load

Many common home and office electronic devices consume energy even when turned off. This is called the “phantom load”, and it can occur with cell phone chargers, appliances with clocks or LED lights, and any device in sleep mode. The Department of Energy estimates that 75 percent of electricity used to power home electronics is consumed while the products are turned “off”.

There are two ways to reduce your phantom load. The first is simply to unplug turned off devices. The second is to plug devices into a power strip, then turn the power strip off when the devices aren’t being used.

Battery Life and Care

When using a laptop, you want the battery to last as long as possible in order to both maximize the time you can use the laptop and minimize the amount of energy you consume. The above power setting advice is applicable to laptops, and here are some more tips specifically for prolonging battery life:

  • Reduce the screen brightness. The dimmer the screen is, the longer the battery will last.
  • Disconnect any external devices not in use. Devices like USB mice and memory card readers consume power even when inactive.
  • Run one application at a time. Multitasking requires increased memory and CPU usage, which in turn drains the battery.
  • Keep the laptop cool. Computing is less efficient at higher temperatures, so make sure the laptop’s inflow and outflow vents are clear. Keeping the battery from overheating (86°F) also extends the overall life of the battery; so please avoid leaving laptops in hot cars, etc.

NOTE: It is not advised to ‘cycle’ the battery of your Luther laptop by draining it completely and then recharging fully.

Although there’s no danger of “overcharging” Luther laptops, leaving a laptop plugged in for weeks at a time can have a detrimental effect on its battery. If you find you are not using the mobility of your Luther laptop, consider switching back to a desktop computer.


Environmental Reports

Computer manufacturers often release reports about the environmental impact and energy consumption of their products. Here are some reports for Apple computer makes and models, many of which are common at Luther: