Energy Calculator PC and Imaging Equipment instructions






power per mode power per mode hours per mode Total Costs
Equipment EUR
On-mode W W hr / day Your electricity consumption
Sleep-mode W W hr / day kWh/year
Off-mode W W hr / day  
  Power management PC+monitor:
months / year airco
Buy or
EUR / monitor
years product life
EUR / system / year
I use a UPS
Electricity Eur/kWh
Add printer
W sleep mode
b/w colour  
TCO (EUR) kWh/yr
Add modem
W sleep mode
TCO (EUR) kWh/yr


Total costs split-up


Energy split-up


Paper and toner/ink
Sleep mode

Calculator history: last 6 calculated results

Click to see settings 1
Total Costs (EUR)


  • You can change values for on/off/sleep modes and hours by using the dropdown lists or you can type any value —e.g. from the ENERGY STAR database— directly into the text boxes.
  • Please do not use the comma sign (,) for decimals. It will not be recognised by the calculator.
  • Explanations can be found when clicking on items.
  • If you click on the 'Calculate!' button, the new output will be added to the Calculator History.



The dropdown lists for 'PC' and 'Monitor' allow you to choose one of 4 presets for the equipment. The values of on-, sleep- and off-mode as well as the purchase prices ('Buy' or Lease) will automatically adjust. You can change these values (click in the box and type), based on the specific values of the equipment you use or intend to buy.
The same goes for the dropdown lists of the 'Use' column, that give presets for typical daily usage.

Presets: PC

Specifications below are typical for January 2012.

Presets: Display

Specifications below are typical for January 2012.

Presets: Use


PC power values are an estimated average for 'Windows or Mac desktop' (= 'on', but processor is hardly working) and 'full load', also weighted for the type of use (e.g. workstation and multimedia PC closer to the full load). Power management features for on-mode (ACPI, Speedstep/PowerNow/etc.) are assumed to be implemented.
Monitor power 'on' values are at default (high) brightness with a primarily light screen.
Hint: Tuning down brightness to a middle level might save you some 15 -20%. At the low brightness level —e.g. featured on many laptops when battery-powered— you could save some 40%.


If you haven't changed the factory power settings, most desktop PCs go into sleep mode if you don't touch them for 20-30 minutes. To fill in the number of hours in sleep just estimate the total time (longer than 20 minutes) you went for meetings, breaks, etc. and subtract 20 minutes for each time event. Also if you don't switch your PC off at night it counts as 'sleep'.

To wake your PC from sleep, you need to press the power button. This is not to be confused with the screensaver-mode, where it is sufficient to move the mouse or touch the keyboard to get a picture on the screen (and which hardly saves any energy). Also, don't confuse it with the hibernate mode, which saves your data on the hard disk and shuts down, if you have enabled this highly energy saving setting (see Power Management to know how). To resume work after hibernating requires a system reboot to bring you back to where you were.

For technical background on sleep see Technical Library (Power Management).


Practically all modern PCs and quite a few monitors (esp. LCDs) use power when switched 'off'.

The only way to avoid this is to unplug them or use the switch on a switchable power strip. If you do that, fill in zero ('0') W in the 'off-mode' boxes for PC and monitor.

0 W "off" mode:
unplug or use the switch on your power strip.

Power Management PC & Monitor

You can choose 3 options for Power Management in the E-Calculator:


Prices (incl. VAT) are estimates, based on 'street'-price offers in June 2010.


Various vendors offer lease contracts for PC systems. Please refer to your lease contract.

Product Life

Default value is 6 years (2003 EU average) for bought equipment. For lease contracts fill in the period indicated in your lease contract.


An Uninterruptible Power Supply (UPS) is an intelligent battery pack to protect your computer (and data) from power surges and black outs. Capacity is dimensioned to allow for a controlled shutdown of the PC. Even a small UPS uses between 8 and 25 W —depending on the model/specs— continuously (8760 hrs/year). If you tick the UPS-checkbox, the calculator assumes a modest UPS for a single PC/small server and adds 87 kWh to your energy consumption and 120 € to your Total Cost-of-Ownership.

Months Room Air-conditioning

When air-conditioning cools your room/office, the heat load of the PC and monitor contributes to the electricity consumption of the air-conditioning installation.
Specify how many months per year the air-conditioning is used for artificial cooling (not heating).

The air-conditioning is assumed to function with an efficiency of 300% (COP is 3.0). Formula: Extra electric energy for air-conditioning= (energy use of equipment/3) * (Months/12).

Electricity Rate

Default value is an average EU figure of approximately € 0.15/kWh as indicated by MEEUP Report (2005). Please apply your local electricity tariff.

Total costs

This is defined as electricity costs + purchase/lease costs + air conditioning costs over product life. If UPS-checkbox is ticked, its price and energy costs are included.

Total electricity consumption

This figure is for the PC equipment and -if indicated by you— UPS and air conditioning.

Add printer / Add modem

If you tick the 'Add Printer' or 'Add Modem' checkboxes, the outcomes of the separate mini-Energy Calculators will be added to your total cost-of-ownership and annual energy consumption (in kWh/year). Just uncheck them and then click the 'Calculate!' button to see what each of these items adds.

Calculator History

The last 5 scores of the Energy Calculator are kept in a separate table, where column '1' represents the actual score, '2' the previous score, etc.
If you click the header ('1', '2', '3', etc.) of a column, the calculator will show the input values that produced those results.

Keeping the score helps you to see if (and how) you are improving. A new score is added (and the oldest score is dropped) each time you click the 'Calculate!' button.

Mini-Energy Calculator for Printers

This calculator lists several inexpensive printers and MFDs (Multi-Functional Devices, combining at least the printer/copier/scanner functions; if a facsimile function is also included it is indicated as 'MFD + fax'). They represent a typical consumer's choice, with speeds in the range of 6-10 pages per minute (ppm) for colour prints and up to 20 ppm for 'normal quality' black-and-white prints. Resolution is in the range of 600x600 or 1200x1200 dpi. Their robustness (indicated by what is known as 'Monthly Duty Cycle') is in the lower ranges (3000 - 10000 pages).

The mini-calculator shows typical presets for purchase price (incl. VAT), paper (plain paper set at around 1.6 to 2 Eurocents/page) and ink/toner costs, electricity rate, a given annual production of 850 pages in black & white and 150 colour pages. The product-life and electricity rate is assumed to be equal to that of the PC system. Only the sleep-mode energy use is given, because at the typically low residential use the extra energy use during printing is negligible.

Mini-Energy Calculator for Modems

This simple calculator distinguishes the three modem types that make a difference in terms of energy consumption: