computer efficiency

Computer Energy Calculator

What are your computers costing in energy and money?
Compare your computers with current efficient desktop, laptop and netbook computers.
Over $100 per computer can be saved per year with simple computer practices.

Computer Energy Calculator Instructions

Fill in the values for your computer situation in the first table.
Press the Get Results button
See the comparison in the second table.
The default computer values used is for a Performance quad PC with LCD monitor.

Computer ParameterValue

Your quantity of computers


Your individual computer power consumption when on in Watts including the monitor.
To work out the computer energy consumption based on its parts see Computer Power Consumption Calculator
Best computer power use measurement results are with power meter over time and average the results.
Otherwise choose from suggested values.
Deduct 20% in desktop computer power consumption if 80 Plus standard computer power supplies are in use.
Deduct 38% in computer power consumption if Computer Power Management is Enabled.
Add 100 watts if the latest graphics processors are used.


Your individual computer power consumption when off in Watts including the monitor (standby).
Best results are with power meter.
Otherwise choose from suggested values.


Power Cost in Dollars per kWh example 0.20


Hours on per week (1-168). Logged out is counted as on. Shutdown = off.


Proportion of time when computer is on but idle over 15 minutes. E.g over lunch or overnight. (0 - 1)


Press button after completing or adjusting fields in the top table. Results are in the lower table.

Suggestions to lower your computer power consumption can include:

  • Turning on Computer Power Management.
  • Use laptops or netbooks instead of desktop computers.
  • Using LCD rather than CRT monitors.
  • Adjust the brightness of the monitor down.
  • Enabling S3 sleep mode in BIOS.

Some sample power consumption values are provided here.
Power meters can be bought for approximately $30 and show real time power use and consumption over time.
How much can you lower a computers power consumption and therefore save energy and money?
Can thin client systems or netbooks be used instead of existing computer equipment?
Is it time to replace the current equipment for newer more efficient designs with lower wattage processors and 80 Plus efficient power supplies?

Computer Energy Calculator Goals

Once you have results, what can you change? Implement computer power management on all computers possible.
Review your yearly computer energy running costs. Is it time to change the hardware mix? Consider all efficiency changes and see which are most appropriate.

Computer Energy Calculator Results

Computer Type

Yearly Power Used
kWh per year

Yearly Power Saved
kWh per year

Yearly Power Cost
$ per year

Yearly Power Saved
$ per year

Your Computer/s



Typical Energy Star 4 Desktop/s



Typical Energy Star 4 Laptop/s



Typical Netbook/s



Does the PC Energy Calculator reveal savings?

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 electrical consumption and running costs can be saved with the above settings.

Energy Control of Computer Peripherals

The simplest method of peripheral control is powering off all peripherals at the wall when the computer is not in use.
Another method is using a USB controlled power board. When the computer turns on the USB voltage enables the special power board to turn on all connected devices.
What is your printer, scanner, speakers, USB hub, external hard drives costing per year to run? Appliance Energy Calculator

PC Power Management Settings for Efficiency on mains and batteries

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