October 17th, 2010
How Wireless Affects Power Consumption Laptop Battery Life
Internet News, by Albel.When we a notebook post the questions that always has to be answered, what battery like on this laptop? We know all manufacturers exaggerate quoted battery life for a system, probably because they test of battery life under ideal conditions for getting a high number. For example, wireless, processor untertaktet, system idle LCD Brightness too low set no DVD and so on. So, if your notebook with a quoted 5 hours gets actually battery life three hours you are wondering what manufacturers have with these other two hours?
The reality is, a great number of things can affect what you do, wireless throughput, processor speed, screen resolution, height the fragmentation of files on the hard disk, LCD Brightness – could the list further and further your notebook battery life. Over the next few weeks we will look at various laptop components as they on battery life, and what can do yourself, to maximize or reduce the amount of power draw, that the component on the system than to take a whole. We are at a high level, so that users understand the average mainstream and use this information to keep and eye glassy when reading. Much of the presented data for research and numbers of Intel it optimization was developed: promoting the mobile series of articles and presentations we have been visited vision of Intel, but we extrapolate the data type of the real world proposals.
The Effect of Wireless on Notebook Power Drain
It is now the year 2007 and 99.9% of all notebooks out there have built-in wireless so you can surf the Web and transfer files via thin air in the form of radio waves (802.11 a / b / g / n). After integrated wireless means have a small chip in your notebook that responsible for sending and receiving the wireless packets’s got. If you are this Web site and wireless Internet access, wireless chip in your PC was required to work and practice a certain power on this page download. If a very small piece of your battery life was stuck pulled the power from the power outlet if you are on battery, donated to downloading this page (we hope it is worth for you).
So, exactly how much does having a wireless radio on and surfing the web affect your battery life? And how much power can you save simply by turning it off? We’ll investigate in this article.
Figure 1 below is that we will refer a lot. There is a bar chart how much power is exercised by the individual components in a notebook. There are five bars, the respectively, how much power on what makes the notebook is used. It is important to note, this benchmarking system on a reference system that did not contain a LCD monitor was carried out. We will consider separate LCD power consumption in another article (it is usually the biggest burden on the battery).
Figure 1: Amount of battery drain of a notebook in various usage states. LCD power drain is not included, the reference system does not include a monitor.
Below is another graph that shows average power drain for four different states of wireless, which are documented below this graph:
Figure 2: Power drain of idle notebook running Windows XP with various WLAN states. Blue indicates power used by all othercomponents, except the LCD power drain which is not included, and purple represents WLAN power drain.
- Power drain of idle notebook (screen power drain not included) with wireless radio Off = 0W wireless radio power consumption
- Power drain of idle notebook (screen power drain not included) with wireless radio On, but not connected to an Access Point (no data being sent or received) = 0.30W wireless radio power consumption
- Power drain of idle notebook (screen power drain not included) with wireless radio On, connected to an Access Point (data can be sent and received) = 0.45W wireless radio power consumption
- Power drain of idle notebook (display power drain not included) with wireless radio On and Searching for an Access Point = 1.6W wireless radio power consumption
Notice that by far the power from the wireless card comes when it scans and attempts to acquire an access point. We charge a worst case scenario for how much the wireless card could affect battery life of a notebook. Meaning, we take the card constantly looking for a network and can never make a find so that the increased power consumption 1.60 W, so:
- Assume average power consumption for notebook with no wireless is 20W
- Assume average power consumption for notebook with wireless, continually trying to acquire network is 21.6W (+1.60W)
The formula for battery life (assuming a brand new battery with no wear on it) is:
- Battery Life = Battery Capacity / Laptop Power Consumption
So if we assume a battery capacity of 53 WHr (fairly standard battery capacity) the formula for battery life with no wireless is:
- Battery Life No Wireless = 53WHr / 20W = 2 hours 39 minutes
And the formula for wireless on and searching for a wireless network is:
- Battery Life Wireless on and Searching for Access Point = 53WHr / 21.6W = 2 hours 27 minutes
So the difference in battery life for this worst case scenario is 12 minutes, which amounts to about 7.5% difference. Now let’s assume the 0.45W power drain for the case where wireless has a solid connection and we’re just transferring a little bit of data:
- Battery Life Wireless Connected = 53WHr / 20.45W = 2 hours 35 minutes
Not bad, only 4 minutes, or 2.5% overall difference!
But, can we always assume 0.45W power drain from wireless? What if we’re uploading and downloading a ton of data, does that affect power drain somewhat? Well, yes…
Wireless Power Consumption Based on Data Transfer Variance
We’re going to look at a comparison of transferring compressed versus uncompressed files to demonstrate the effect the amount of data transferred has on power consumption.
You must be aware that you transfer more data depending on the WLAN card has more to work, which means has to consume more power. So if you several gigabytes streaming video files from a media server in your home to your laptop unplugged, sweating your wireless card is hard and do be a lot of work, thus draining battery faster. If your notebook is that wireless, is firmly connected and everything you do emails check the wireless card is hardly sipping power every 5 minutes and have little effect on battery life.
Let’s look at how amount of data transfer affects energy used with some charts and graph comparisons.bbAssume we have 5 different files, each file can be compressed to varying degrees using GZIP:
| Data Set | Original Size (KB) | Gzip Compress Rate (version 1.2.4) | Description |
| Tulips.tif | 1179 (1.15MB) | 1.2x | Med size file, very low compress ratio |
| Book1 | 751 (0.73MB) | 2.45x | Med size file, low compress ratio |
| World95.txt | 2935 (2.87MB) | 5.06x | Large size file, high compress ratio |
| Pic | 502 (0.49MB) | 8.96x | Small size file, high compress ratio |
| Frymire.tif | 3708 (3.62MB) | 14.04x | Large size file, very high compress ratio |
Tulips.tif is almost incompressible, while Frymire.tif can be compressed to almost 14x smaller than its original size. Here’s a chart showing how long it takes to download the uncompressed file versus downloading a compressed version of each file plus the amount of time it then takes to then uncompress that file once it is downloaded:
Keep in mind that we are about 2.5 minutes saving with Frymire.tif, by you the much smaller zip up version of the file and then unzip it. Now the file is about the same size as uncompressed, compressed Tulips.tif and then we have time and unpack spend processing power more time and energy as a whole, so that it lands!
The amount of time it takes to download a file and then uncompress a file has a very direct effect on power consumption. Notice in the graph below how much less energy it takes to download the compressed version of Frymire.tif:
Several times more energy is consumed to download the uncompressed original 3.62MB size Frymire.tif, it took almost 3 minutes to download Frymire.tif, so the wireless card is working all that time.
When you download a web page, most websites (such as this one) actually send a page in gzip format and your browser will unzip it on the fly. So this type of thing is constantly going on behind the scenes as you browse the web. The more web pages you download and browse, the more power it takes.
The moral of the story? The more you’re downloading with your wireless card, the more power it consumes, so the effect your wireless card has on battery drain depends a lot on how much you’re using it.
Conclusion
For those that saw a couple of formulas and graphs and skipped ahead to this part, I don’t blame you, here are the take aways based on the data:
- Simply turning on the wireless card doesn’t drain much power, it might shorten battery life by 2%, so if you want to remain connected to download email it’s no big deal.
- If you turn on wireless and are constantly trying to acquire a connection, such as if you’re constantly dropping a connection and then trying to reconnect, your battery life could be 6% – 7% shorter than usual due to the wireless card having to work extra hard.
- If you have wireless card on and are transferring lots of data, such as downloading large files or constantly browsing the web, battery life could be about 6% shorter than simply no wireless on. Consider downloading large files later when you’re plugged in.
- If you don’t need to use the web, turn wireless off, it’ll save you at least a few short (but maybe precious) minutes of battery life!
Overall, I believe that energy consumption due to wireless is a bit like a culprit for Notebook battery discharge exaggerated. You can save much more performance by dimming display brightness underclocking the processor, Spinn DVD of less, or a host of others we will find sleep tactics in future articles. In most cases you will have much more fun or even more productive when connected to the Internet, so do not sweat, turn on the wireless card and more productive with this time you have on the battery.
Wireless is a huge battery and energy drainer. That’s why you should plug in whenever possible, especially if you’re in an office all day. You can also find other ways to save energy consumption by using tools like the IT Carbon and Power Consumption Calculator. It’s a real eye-opener!