Energy Calculator for Computers

The calculated values are based on 240 days of use per year. Click here for instructions

 INPUT

 

Computer

Display

Use

Equipment

power per mode:

power per mode

hours per mode

On-mode

W

W

hr / day

Sleep-mode

W

W

hr / day

Off-mode

W

W

hr / day

 

Power management computer+display:

months / year airco

Buy

EUR / system

EUR / monitor

years product life

or Lease

EUR / system / year

I use a UPS

Electricity EUR/kWh

 

OUTPUT

Total costs split-up

EURO

 

Energy split-up

kWh/year

Equipment

Energy

Paper and toner/ink

Total

On-mode

Sleep-mode

Off-mode

Air-conditioning

Total

Total Costs: EUR

Electricity Consumption: kWh/year

More information

Click to restore settings

1
newest

2
previous

3
 

4
 

5
 

6
eldest

Total Costs (EUR)

kWh/year

Instructions

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Equipment

The dropdown lists for 'Computer' and 'Display' allow you to choose a 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.

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Presets: PC

Specifications below are typical for March 2017.

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Presets: Display

Specifications below are typical for March 2017.

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Presets: Use

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On-mode

The on-mode of the computer is the state in which the computer is actively used and/or idle. The idle mode the most determining factor in the power consumption of a computer. You can use the 'Short idle mode' power values of the computer database, which best represents the On-mode power. In the calculation the long idle mode is 90% of the short idle mode, which is the average ratio from the products database. The time ratio spent between short idle and long idle mode is 32:10, which represents the average mode weightings ratio for these power consumption modes in the TEC calculation of Computers 6.1. Power management features for on-mode are assumed to be implemented.

Display power 'on' values are at default brightness setting.
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%.

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Sleep-mode

Sleep mode is a low power mode that the computer enters automatically after a period of inactivity or by manual selection. The computer saves its data into its RAM. A computer with Sleep capability can quickly “wake” in response to network connections or user interface devices with a latency of less than or equal to 5 seconds from initiation of wake event to system becoming fully usable including rendering of display.

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

To wake your computer from sleep, you need to press the power button. This is not to be confused with the screensaver- or blank mode of the display, where it is sufficient to move the mouse or touch the keyboard to wake the display. A screensaver does not save any energy. It is better to choose blanking the screen.
Also, don't confuse sleep with the hibernate mode, in which the computer saves your data on the hard disk and shuts down. Hibernating is the highest energy saving mode. Resuming work after hibernating requires the computer to boot up to bring you back to where you were.

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Off-mode

Practically all modern computers and quite a few displays use power when switched 'off'.

The only way to avoid this is to unplug them or use the switch on a switchable power strip. In such a case, fill in zero ('0') W in the 'off-mode' boxes for computer and display.

0 W "off" mode:
Unplug or switch off your power strip.

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Power Management computer + display

You have 3 options for Power Management in the Calculator:

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BUY

Prices (incl. VAT) are estimates, based on 'street'-price offers in December 2016.

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LEASE

Various vendors offer lease contracts for PC systems. Please refer to your lease contract. The duration of the lease contract can be entered in the field Product Life.

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Product Life

Default value is 6 years (2003 EU average) for bought equipment. For a different product life or for lease contracts enter the desired number of years.

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UPS

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.

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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).

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Electricity Rate

Default value is an average EU figure of approximately € 0.206/kWh as indicated by EuroStat (households in EU-28, november 2016). You can apply your local electricity tariff.

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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.

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Total electricity consumption

This figure is for the whole equipment and any UPS and air conditioning.

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Calculator History

The last 5 results of the Energy Calculator are kept in a separate table, where column '1' represents the actual result, '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 track of the results helps you to see if (and how) you are saving energy. A new result is added (and the oldest result is dropped) each time you click the 'Store in calculator history' button.

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