The Power Calculator Help page documents methods, terminology and references used in
the online power calculator. The computer hardware included for calculation:
Motherboard, CPU, Graphics Card, Hard Drive, Other Drives, Memory, PCI Expansion
Cards, External USB, and Case Cooling Fans.
General System Description. Classification used to size motherboard
sans CPU, expansion cards, and memory. Typically between 20-50W.
Besides high performance graphics cards, the CPU will
consume more power than any other hardware component. For this reason, our calculator
has focused on providing extensive CPU coverage (over 1000 models) and information for Intel and AMD
processors. Besides Thermal Design Power (TDP
or equivalent value, each selected CPU will also provide on board cache, core design,
codename, socket, and available part numbers. This information has been compiled from
and CPU World
Unlike CPU manufacturers, many video card
makers do not publish power requirements. This is unfortunate on a number of levels,
the primary being adequate information for proper power supply selection.
X bit labs
has conducted several outstanding
studies on graphic card power consumption. The most recent
was performed across different manufacturers and categories. Our
calculator takes an average from each of the 5 categories. The categories are presented
as selection options.
• Premium: Highest performance graphics
cards available. Described by fan speed regulation, dual-slot cooling design, top 3D speeds exceeding
1.55GHz, length 22.8cm or greater.
• High-End: Step below Premium. Fan speed regulation,
usually single slot cooling design, top 3D speed below 1.5GHz, length 22.8cm or shorter.
• Performance-Mainstream: More appeal to mass market with lower
price points. Fan speed regulation, usually single slot cooling design, top 3D speed below 1.0GHz, length 21.8cm or
• Mainstream: Upgrade option founds on built it yourself PC sites
such as Dell. Usually has fan speed regulation, usually single slot cooling design, top 3D speed below 1.0GHz, length
20cm or shorter.
• Entry-Level: Default card included with most modern PCs. May
include fan speed regulation, single slot cooling design, top 3D speed below 1.0GHz, length 18.8cm or shorter.
Hard Drive. X bit labs
and tom's hardware
both have performed detailed hard drive power
consumption tests. The power calculator has synthesized results from both studies. For most application users, the
best approach is to select based on hard drive size (3.5", 2.5", or 1.8") with 3.5" being the most
common desktop form factor. Also included from the X bit report is 35 common hard drives by manufacturer and model.
Drives consume the most power upon start up. Both reading and writing are also power intensive operations, nearly
matching startup in certain cases.
Other Drives. Other drives such as CD-ROM, DVD-ROM, CD-RW, DVD/CDRW Combo, and DVD-RW/DVD+RW
consume maximum power values between 20-30W.
Memory. Memory is one of the more difficult hardware components to accurately measure. A
memory module is composed of several chips or integrated circuits. These circuits require power to operate and
define "how much". The Calculator makes an educated guess based on the memory technology and number
PCI Expansion Cards. The PCI specification requires expansion cards to communicate power needs. Two
pins (PRSNT1# and PRSNT2#) are used to signal maximum power of 25W, 15W, or 7.5W. For simplicity the calculator take an
average of these values and assigns each PCI Expansion card 15.8W.
External USB devices are consume very little power. The calculator assigns 0.5W for
each device. A detailed analysis of several USB components can be found on
Case Cooling Fans. Case cooling fans will draw between 0.2 - 2.0W depending on fan speed. A case
fan is assumed to be 80mm in size. Larger fans such as 120mm will consume slightly more, up to 2.5W.