Building a Low-Power Computer

By Stealth1 Comment

When it comes to your power bill, less power used by computers and equipment means more saving on the power bill every month. I’ll explain in this post how I built a couple personal servers that not only take much less power, but are 100% silent as a bonus feature — WITHOUT sacrificing performance.

A computer running full-time can easily take 144 kilowatt (kWh) hours each month, which based on average power rates (12 cents per kWh in December 2011) could be around $17 each month on your power bill. I have seen power rates as much as 50 cents per kWh in some areas.

Calculating Power Usage

Take the wattage it draws from the wall outlet. For computers this is NOT the wattage the power supply is able to provide to the system, it should actually be lower and is generally about half of that value. This is due to the voltage being stepped down, which creates more power. Depending on your power supply and it’s specifications, this could vary. Take the number then multiply it by 0.720, which is the number of hours in 1 month divided by 1000 (to skip dividing by 1000 to get kWh later). This will give you the kWh your computer uses, then simply multiply that by your current per-kWh rate. This equation looks like: ((<output wattage> / 2) * 0.720) * <kWh rate> For my desktop, this would be ((300 / 2) * 0.720) * 0.17 = $18.36/month to run 24/7.

Alternatively, you can get your hands on a Kill-a-Watt meter and measure your computers power draw directly. I do recommend checking the accuracy of your meter by using a standard incandescent light bulb. Remember to ensure you don’t exceed the meter’s maximum load. Take the resulting wattage (adjusted for any margin of error from your meter) and multiply it by 0.720, then again by your current power rate.

Hardware

Most of the hardware I use for low power and silent systems comes from www.mini-box.com. Each item is generally purchased individually exactly as you would with a full-sized computer. The hardware I used is all in the Mini-ITX form factor which keeps things small and manageable. There are also “nano” systems, however there are no common standards for the hardware, making those harder to build and manage.

Motherboard and RAM

Mini-ITX form factor mother boards come in a variety of specs for different purposes. You have the option of using a full-sized CPU, or something integrated and permanently affixed to the motherboard. For low-power applications it’s best to stick with the integrated processors since they generally require less power to operate. The drawbacks to integrated processors is you do not have the option to upgrade it later if you needed more speed (but how many people upgrade JUST the processor in a system).

If you are connecting this system to your TV to watch videos, choose a motherboard with a decent graphics processor. Most Mini-ITX boards are designed for integrated applications and won’t have very many supported display features (such as a large resolution selection, 3D acceleration, adjustable or lots of video memory, etc). If going with better graphics features, keep this in mind when choosing your power supply.

If your pondering using the system as a file server, it’ll be easier to get one with an eSATA port on the back than to fashion your own down the road with a SATA-to-eSATA adapter. You’ll likely also want a system with a gigabit ethernet port.

The motherboard I went with is the Intel D2700MUD, which sports a 2.13 GHz dual-core Atom (low power!) processor. It has 2 memory slots for up to 4GB of memory, a PCI slot, and a mini-PCI Express slot.

As for RAM, just pick your desired amount of memory that is compatible with the motherboard. ITX motherboards may have either SODIMM and SDRAM slots, and may be DDR2 or DDR3. Be sure you check with the specs of the motherboard you choose for the maximum supported memory per slot.

Mass Storage

For mass storage (hard drive) you have many options. All modern ITX boards come with SATA connectors so it is down to deciding what type and how much storage you wish to put in your system. You can use a 3.5″ desktop hard drive (if your case allows), 2.5″ laptop hard drive, SSD, or Disk on Module (DOM).

In most situations your desired case determines the type and size of the mass storage device you add to your system. Alternatively, if your motherboard permits, you can use external storage (eSATA would be best) and have your drive(s) in an external case with their own power supply.

For my system I used an 8GB SATA DOM. 8GB is generally plenty for a webserver, personal space (SSH access, minor file storage), and operating system.

Case and Power Supply

The case for your system is another item that would be your preference. When building systems I generally choose my desired case, then find the power supply to fit it. For my system since I am going with a fanless setup, I chose the M350 Mini-ITX case. It has enough room for the motherboard, and comes with a bracket for either 1 HDD or up to 2 fans (40mm).

For the power supply I went with the picoPSU-80 which outputs 80W, which is plenty to drive the motherboard and DOM. This power supply plugs directly into the motherboard’s power connector and has a pigtail for 12V input. Some ITX motherboards have other connections or components too close to the power connector to use this type of power supply. If ordering from Mini-Box there will be a note on the motherboard’s product page if it cannot be used with a picoPSU. Also be sure you choose the proper 12V power supply for your setup!

If going with the M350 case and picoPSU-80, Mini-Box has a bundle with the picoPSU-80, M350, and 12V power adapter for a little less than buying those parts individually.

Extras

Now that we’ve got a basic system, there might be some extras desired.

Mounting Options

Depending on your case, there might be some mounting options. Some cases have the ability to be mounted on the back of monitors with VESA mounting holes, on the wall, under a desk, between a monitor and the wall, or even to utility rails. Consider where you wish to put the system, then plan accordingly with the case and your parts order.

Internal Hardware

Consider what your purpose for this system is. If you need to get another bracket for mounting and other HDD or a fan, it would be best to order these wtih your case.

Additionally, based on your environment and mounting you might want to install a wireless card (not recommended for server applications). Be sure to choose one that will work with your motherboard and case. Keep in mind many Mini-ITX cases don’t have space to use the full-size expansion slots.

A Fan

You may have read through all this thinking a fan may not be needed. Depending on your environment, that may be true. If the environment this system is going to be running in gets hot or may be an enclosed space, you might want to consider putting in a fan just to further ensure your system’s stability. When working with a fanless system, I always go with “if it’s too hot for me, it’s too hot for the computer.” You might have the ability to switch on the AC, but your computer doesn’t always have this luxury when you’re not around. A fan would ensure airflow (though warm) is maintained.

I will be using a fan in my setup, and I have wired in an on/off switch so I can have it on for warmer days, but off on the cooler days.

Putting it All Together

A summary of the components I am using for my setup:

  • Intel D2700MUD ITX Motherboard
  • 2GB DDR3 SODIMM RAM
  • picoPSU-80 (and 12VDC/5A power supply)
  • M350 fanless Mini-ITX enclosure
  • 8GB SATA DOM
  • 40mm Fan

When put all together, this system draws 15-20W of power. When compared to the 80W my current server is taking, giving me a minimum savings of 75% each month to run. If my power bill averages 17 cents per kWh, this will be cost $1.84~$2.45/month to run versus the current server at approximately $9.80/month

Additional Notes:

Note about wattage measurements: Watt usages were measured using my Kill-a-Watt meter (model P4400), which has shown to have a +/-1% margin of error. This was determined by plugging in a 100W light bulb, in which the meter displayed 99W being used.

Note about hardware: Through this blog I have given information on how to assemble your own low-power computer or personal server with my own personal server as an example. This information is provided for informational purposes, please do ensure you check all environmental and power requirements. Exceeding power ratings on power supplies and systems may be a fire hazard. I am not responsible if you burn down your house because you didn’t do the calculations and your system and/or power supply melted down.

Hardware

One Comment to “Building a Low-Power Computer”

  1. burberryoutletn says:

    I always was interested in this topic and nonetheless am, regards for posting .

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