Notebook Computers

Notebook computers consume much less power than desktop systems. First, notebook computers use energy-saving LCD monitors. Second, the CPU, components and software in a notebook computer are designed to conserve power so as to maximize battery operation times. Third, notebooks use external power supplies that are much more efficient than the power supplies used in most desktop systems.

When describing the power consumption of notebook computers, the power consumption of the monitor is automatically included because the display is integrated into the unit. A few years ago, notebook computers typically ranged from 15 - 20 W power consumption with average consumption for the class of 15 W (Ref). As of 2004, the average power consumption of new notebook computers is beginning to spread over a wider range, from about 10 W to 50 W. Whereas notebooks used to be designed primarily for business users whose primary requirements were portability and long battery life, they are now also serving as desktop replacement units and DVD/multimedia systems. These market changes have contributed to the higher power consumption reported for some models.

Particular notebook models and power-saving technologies change rapidly in the fast-moving computer market. At the time of publication, typical notebook computers ran for 2-3 hours on a fully charged battery.

Notebooks based on Intel’s Pentium M processor – which includes those labeled as Centrino technology – advertise 4 to 5 hours on their main batteries (Ref). Using two batteries, some notebooks advertise battery life of up to 10 hours (Ref). Intel’s Centrino technology, introduced in March 2003, is actually a combination of three Intel components used together: the Pentium M processor, the Intel 855 companion chipset, and a WiFi wireless Ethernet chipset. External lithium ion battery packs, small solar chargers, DC-DC adapters and other accessories can be purchased to extend the mobile runtime of notebooks.

Recent generations of mobile processors reduce power consumption by clocking down the processor frequency and stepping down the supplied voltage when battery life needs to be extended. Battery extending notebook technologies such as Intel’s SpeedStep, AMD PowerNow! and Transmeta LongRun automatically clock down the CPU in certain situations, such as when the notebook loses AC power and switches to the battery, while the system is idle or when the applications running on the notebook don’t require maximum processor performance. For example, a 1.4GHz Intel Pentium M processor can clock down to as low as 600 MHz. When this happens the drain on the battery is reduced.

Notebook power-saving technologies are frequently subject to user modification through the computer’s power management settings. The user can choose settings that guarantee maximum processor performance, maximum battery life, or settings in between. The exact settings depend on the type of processor, manufacturer, the driver software and the operating system installed on the notebook.

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