How efficient are PCs

How to Lower Your PC's Power Consumption?

A study by Energie Agentur.NRW shows that a quarter of electricity consumption is accounted for by PCs, printers, WLAN routers and the like - even before the refrigerator and washing machine. We explain how you can get the power consumption of your computer and router under control and thus save a lot of money.

You can basically save energy in two ways: by purchasing particularly energy-saving PC components and by cleverly using the existing equipment.

Electricity consumption increases

Fifteen years ago, the average consumption for computers, televisions and the like was seven percent. Only every fourth household even owned a PC. Today computers, routers, satellite receivers and much more account for almost 25 percent of electricity consumption.

Longer usage times, more devices and larger screens are the main reason for the increasing energy consumption, writes the Energie Agentur.NRW. The PC is used around five hours a day, and standby times are around nine hours a day.

Save with old PC hardware

If your PC is a few years old but you are basically still satisfied with its performance, not having a new PC is probably the best way to save energy. About 3000 kWh of energy have to be used to manufacture a single computer: this corresponds roughly to the annual consumption of a small household.

It therefore makes sense to distribute this energy expenditure over the longest possible useful life. But the continued use of an old device can also have a positive effect on your own electricity bill - if it is the right one.

Old PCs often use less power

Computers that were mainly used for office tasks ten years ago, i.e. are equipped with a simple on-board graphics card and a processor between one and two GHz, often only consume between 30 and 50 watts.

A modern PC with a multi-core processor, on the other hand, can easily use 100 watts. With four hours of use per day and a gross price of 0.25 euros per kWh, a modern PC (without monitor and other peripherals) consumes electricity for 36 euros, while an old computer costs an average of 14 euros.

TFT flat screen saves energy

However, the PC monitor is left out of this calculation. Here, the good old tube devices consume four times more energy: the typical consumption of a tube monitor with a 20 inch diagonal is over 100 watts, while a TFT flat screen of the same size only consumes around 25 watts. With another four hours of daily use, the old tube costs 36 euros per year, while the TFT screen only sucks electricity from the line for 9 euros.

When using the monitor, the power consumption in standby mode must also be taken into account. A study by the company MMD found in 2013 that almost two thirds of all monitors are not switched off after shutting down the workstation PC. With 28 million workstation computers in Germany in 2012 and a potential saving of up to 26 euros in electricity costs per monitor per year, total costs of over 480 million euros result, which could be avoided, the study calculated.

This is associated with higher carbon dioxide emissions: if the monitor is switched off consistently, up to 1.6 million tons of CO2 the study calculated that fewer are emitted.

New purchase: Notebook beats desktop PC

Before purchasing a PC, you should consider which performance features are important to you: If mobility is the top priority, then congratulations: Even the high-powered notebooks rarely consume more than 50 watts.

Most tablets even consume less than 10 watts, and thus cost just 3.60 euros of electricity per year (again assuming four hours of daily use and an electricity price of 0.25 euros per kWh).

Energy can also be saved with the desktop PC

However, the desktop PC also offers considerable savings potential, depending on the preferred use: A quad-core processor consumes 10 to 20 watts more energy than a dual-core processor at full load, and a separate, high-performance graphics card up to 100 watts more than an on-board processor. Solution.

If you use a PC almost exclusively for office tasks, edit photos and watch slide shows and videos, a simple two-core with on-board graphics is completely sufficient. However, if you regularly edit videos, attach importance to HD resolution or are a fan of graphically demanding computer games, you have to dig deeper into your pockets.

Save energy with the graphics card

The choice of graphics card in the PC can also help reduce electricity costs. While the manufacturers rarely reveal directly how much power their graphics cards consume under normal conditions, a value has been established in marketing from which the energy efficiency can be inferred at least indirectly: TDP, written out as Thermal Design Power.

This value indicates the maximum thermal power loss: the higher the value, the more energy is lost in the form of heat instead of being reflected in graphic performance. In addition to the benchmarks often cited by manufacturers, the TDP is therefore an important comparison criterion.

What to watch out for with power supplies

You can also save electricity by choosing an energy-efficient power supply unit. Frequent misunderstanding: A 300 watt power supply does not necessarily consume more power than a 250 watt power supply; the value rather indicates the maximum amount of power it can provide to the PC. In principle, the output of a power supply unit should be selected so that it is at least twenty percent higher than that of all components to be supplied.

On the other hand, one feature that you can use to assess the energy efficiency of a power supply unit is the initiative's seal of approval 80 plusthat is only allocated if a power supply unit achieves an efficiency of at least 80 percent at 20, 50 and 100 percent load. For the higher certifications "80 Plus Bronze", "80 Plus Silver", "80 Plus Gold" and "80 Plus Platinum", the efficiency requirements have been increased in stages according to the following table:

Efficiency at

20% occupancy

50% occupancy

100% occupancy

80 plus




80 plus bronze




80 Plus Silver




80 plus gold




80 Plus Platinum




Save energy under Windows

How much energy a PC consumes depends not only on its hardware, but also on how it is used - and above all, what happens when it is switched on but actually not needed.

Real energy throws are sophisticated screensavers. They often ensure that energy consumption even increases: CPU, graphics card and monitor drive such a screen saver to maximum performance. How much energy you save by simply letting the screen go black instead of complex animations during work breaks naturally depends on how many breaks you take.

Right-click on the desktop and the menu entry Settings respectively (since Windows Vista) To adjust takes you to the screen saver dialog. How you can reduce the energy consumption of your PC even further from there, you can find out in the photo show Save energy under Windows.

Save energy on the wireless router

Modern routers have a night service that stops operation at night when the PC is switched off and users are asleep. You can use the user interface to set times at which the router switches off the WLAN function if no device is active in the wireless network. Tip: In single households, the night service can also be activated during the day when you are at work anyway.