Green IT Concepts: Real Life Energy Use
Author: Mike Lovell
Date: July 27, 2009
Some of the concepts of Green IT can be a little complicated. Fortunately, this one is not. For this article, I am going to look at the basics of real world computer energy use. And what better way to do that then to use computers around my own home? Fortunately, these four machines are all very different from each other, so we'll be able to see a fairly wide spectrum of computer energy use.
This will give us a bit of perspective on how much energy a common computer uses and how its energy use is dependent on the amount of work it is doing.
The Computers
|
The Shuttle
System specs:
Age of parts: 4-4.5 years |
The Gamer
System specs:
Age of parts: 1-2 years old |
|
The Pretty One
System specs:
Age: 1.5 years |
The EEE
System specs:
Age: 1 year |
To find out the power usage of these machines, we are going to look at two very specific scenarios. We will check out energy use when idle (booted up, but not running anything) and when they are at full load (using 100% of the CPU). I will throw in some other considerations as well.
To monitor the energy use, I used a simple Kill-A-Watt meter hooked up to only the laptops for laptop testing and only to the computer cases for desktop testing. Monitors are not included in these tests.
To get the machines at idle, I booted them up and waited approximently five minutes so that everything was loaded and the CPU was at 0% or close to 0% with no programs running. To get the machines running at full load, I used a simple pi calculation program called prime95. It uses multi-threading and pure mathematical calculation to ensure a CPU is running at full capacity.
Let's look at the power usage of these machines:
| Shuttle | kWh | Annual cost of Running 8 hours a day | Annual cost of Running 16 hours a day | Annual cost of Running 24 hours a day |
| Idle | 85 | $29.26 | $58.53 | $87.79 |
| Full Load | 134 | $46.13 | $92.26 | $138.40 |
| Gamer | kWh | 8 hours a day | 16 hours a day | 24 hours a day |
| Idle | 129 | $44.41 | $88.82 | $133.23 |
| Full Load | 189 | $65.07 | $130.13 | $195.20 |
| Gaming | 208 | $71.61 | $143.22 | $214.82 |
| Pretty Laptop | kWh | 8 hours a day | 16 hours a day | 24 hours a day |
| Idle | 28 | $9.64 | $19.30 | $28.92 |
| Full Load | 61 | $21.00 | $42.00 | $63.00 |
| EEE Netbook | kWh | 8 hours a day | 16 hours a day | 24 hours a day |
| Idle | 16 | $5.51 | $11.02 | $16.52 |
| Full Load | 23 | $7.92 | $15.84 | $23.75 |
Costs Calculated using Nova Scotia home energy rate of $0.1179 per kWh.
What can we tell from these numbers? The first, and most obvious, thing we see is that all of these computers use more energy when running at full load than at idle. This may not be a startling revelation to most, but the delta might be. This clearly shows that there is a huge difference in energy use depending on how the computer is being used.
The second thing we can see that the two laptop computers use significantly less power than the two desktop computers. Even though the Shuttle is a small form factor computer, it still uses a great deal more energy than both of the laptops. Laptop hardware is designed to run on battery power, so it is no surprise that it is designed to be as energy efficient as possible to ensure a longer battery life. It has become common for computer manufacturers to build "green" desktop computers using parts originally designed for laptops.
The next thing one may notice is that a modern computer like the Inspiron laptop can use a lot less energy than a computer with older hardware like the Shuttle even though the Inspiron has significantly more computing power. However, there is another side of this coin.
As we can see, the computer that uses by far the most energy is the quad-core powered gaming machine. This shows that there is still a lot of opportunity for system builders to create a computer that can still eat energy. It is important to stress that a computer this powerful may be more than what most users need and if underutilized they can do more harm to your energy bill than necessary.
Conclusions:
What can we take from all of this?
First, the most important thing one can do when trying to become greener with their computer is to not buy more computer than they need. Newer hardware has the potential to use less energy, but there is no guarantee that it will. Consider what the computer will be used for and buy its components accordingly. Refer to our Green Computing Guide for help.
The other thing that can be seen is computers use a lot more energy when performing tasks than when they are doing nothing. Be sure that your computer is not being overtaxed by programs that you are not using (particularly programs running in the background). Also, ensure your software and virus scanner is up to date so that malware and viruses are not using up computer resources and, ultimately, costing you energy and money. We can also see that shutting down a computer when it is not being used (especially powerful machines designed for gaming) can save a significant amount of energy and money on a power bill.
Bonus: Overclocking
As a short aside, I thought I would add the results of my testing when my gaming machine is overclocked. Without getting too much into how overclocking works, I want to show the huge impact overclocking has on the amount of energy a computer uses.
| Gamer running at 3.6GHz | kWh | 8 hours a day | 16 hours a day | 24 hours a day |
| Idle | 203 | $69.89 | $139.77 | $209.66 |
| Full Load | 351 | $120.84 | $241.68 | $362.51 |
| Gaming | 309 | $106.38 | $212.76 | $319.14 |
As you can see, this overclock causes the computer to use 57% more energy at idle and 86% more when at full load. When we throw a game into the mix (which throws the power use of the video card into play) we see the energy use is not quite as high because the CPU is not as taxed, but the energy use is still very high. As you can imagine, this also increases the amount of heat generated by the computer, turning it into quite the space heater.
