How to Calculate Computer Wattage
Building, upgrading and maintaining your own computer is a fun and rewarding way to customize your perfect system and keep it performing optimally. When you plan a do-it-yourself computer hardware project, whether it's a brand new box or just a major upgrade, ensuring you have the right power supply is critical. The power supply provides electricity to everything in the computer, from the motherboard to the keyboard. If a too-small supply starves the computer for power, it may misbehave, leading to problems like unexpected reboots and components not working. Power supplies and component power consumption are measured in watts.
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Instructions
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Include every component attached to the motherboard or power supply. List every component fed by the power supply, including the motherboard, CPU, fans, add-on cards, memory and drives as well as devices like the keyboard and mouse. Do not include externally powered items, like your monitor.
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Look in the components' technical specifications for the power rating for each component and write it down on your list. The value should be stated in watts (abbreviated "W"). Use the "peak" or "maximum" rating if it is provided. If you cannot find it in the technical specifications, try searching the web for the component name and model plus the term "power requirement." If you still come up empty-handed, use the highest value in the table on the "PC Power & Cooling: Power Usage" web page linked in the References section below.
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Add up all the power wattage values on your list to get the total wattage for the system. If you have multiples of the same component (for example, three memory cards), remember to count them separately (so, three memory cards at 12W per card would add 36W to the total).
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Multiply the total wattage by 1.3 to get the system power supply unit requirement. That adds a 30 percent buffer to your total to account for future upgrades, peak power usage and any component you may have missed.
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Tips & Warnings
Many computer power-usage calculators are available online to help you estimate wattage for your computer system. See the Resources section for a list of a few of these calculators or search the web for "computer power supply calculator."
When purchasing a power-supply unit (PSU), make certain you buy one compatible with your computer case. PSUs generally have a listed computer form factor (size and shape), such as AT, ATX, or microATX. Use a PSU that has the same form factor as your motherboard and computer case.
References
Resources
- Photo Credit power supply cable image by Christopher Meder from Fotolia.com carte mere d"ordinateur image by Jerome Dancette from Fotolia.com
