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Computer Power Consumption Calculator Computer Power Consumption Calculator

Computer Power Use Calculator

What size computer power supply do I need?

What options in computer power supplies can save on energy, heat output and money?

Over $100 per computer can be saved per year with simple computer choices.

Computer Power Consumption Calculator Instructions

Fill in the values for your computer components in the first table.

Press the Get Results button

See the computer power consumption and options in the second table.
Quantity Description
Computer Classification
Processors Type
Graphics Card/s Type
Hard drive/s Type
Optical drive/s CD, DVD, DVD-RW
Memory Module Type
Internal fans including CPU fan
Expansion Slots Used
USB or Firewire devices attached

Press button after completing or adjusting fields in the top table

Once you have results, what choices can be made?

Suggestions to lower your computer power consumption can include:

  • Select the best 80 Plus standard power supply possible
  • Measure exact computer power consumption with a power meter.
  • Turning on Computer Power Management.
  • Using LCD rather than CRT monitors.
  • Enabling S3 sleep mode in BIOS.
  • Note the measured savings made with the configuration changes.

Local links: Matthewb Homepage , Energy Efficiency Section , Efficiency eBook
Computer Energy Yearly Costs Calculator

Computer Power Use Calculator Results

Parameter Value
Nominal Power Consumption watts
Maximum Power Consumption watts
Power Supply Rating Suggested watts
Regular Power Supply Nominal Input Power watts
80 Plus Power Supply Nominal Input Power watts
80 Plus Power Supply Nominal Savings in Power watts




Check your motherboard manual for minimum power supply rating for safety. Consider future expansions in you power supply rating calculations.

Server power supply EPS specifications can go up to 800 Watts

Blade server chassis power supplies support multiple servers. Each power supply ratings can be 2200 Watts each. Multiple power supplies are used for redundancy.

Computer Power Management CPM defined

CPM is a way to save energy consumption of a computer using only configuration changes. Suggestions for energy saving settings are:

  • Turn off screens after 15 minutes of inactivity. This is configured in the operating system to operate automatically.
  • Turn off hard drives after 15 minutes of inactivity This is configured in the operating system to operate automatically.
  • Make computer go to sleep or hibernation after 30 minutes of inactivity. This is configured in the operating system to operate automatically.
  • Enable in the computer BIOS: ACPI, S3 Sleep Mode, Intel Speedstep / AMD Cool n Quiet
An extra 38% in electrcal consumption and running costs can be saved with the above settings.

Computer Power Use Calculation Background

The computer power supply rating is higher that the power use maximum to cover the initial power use surge at start up. Other factors include running computers in non air conditioned rooms and poor ventilation areas. 80 Plus power supplies generate less heat and create less heat related issues.

Computer processors now come in many varieties. Some processors come in multiple classes with different power consumption levels. Often newer processors with smaller transistor sizes use less energy with the same or better performance levels.