Hardware Secrets
Home | Camera | Case | CE | Cooling | CPU | Input | Memory | Mobile | Motherboard | Networking | Power | Storage | Video | Other
Content
Articles
First Look
Gabriel's Blog
News
Reviews
Tutorials
Main Menu
About Us
Awarded Products
Compare Prices
Datasheets
Dictionary
Download
Drivers
Forums
Links
Manufacturer Finder
Newsletter
On The Web
RSS Feed
Test Your Skills
Twitter
Newsletter
Subscribe today!
Search




Recommended
Switching Power Supplies A to Z
Switching Power Supplies A to Z, by Sanjaya Maniktala (Newnes), starting at $43.50
Home » Power
Everything You Need to Know About Power Supplies
Author: Gabriel Torres
Type: Tutorials Last Updated: May 29, 2008
Page: 9 of 14
$ Check REAL-TIME pricing for Thermaltake Silent Purepower W0100 - power supply 500 Watt and other Internal Supplies at CDW.com W0100RU $.
CDW: $75.99 Directron: $54.99
Newegg: $59.99 CircuitCity: $59.99

Efficiency

The efficiency of a power supply shows how much from the power being pulled from the power grid is being effectively converted into DC. Efficiency is the ratio between the power being pulled from the wall and the power actually being delivered to the PC.

Efficiency = DC power / AC power

For example, if your PC is consuming 250 W and your power supply is pulling 350 W from the wall, this means that your power supply efficiency is of 71.4%.

Good power supplies will provide an efficiency of at least 80%, the higher, the better. We recommend you to buy power supplies with at least 80% efficiency.

A power supply with higher efficiency brings two advantages.  First, a lower electricity bill. Using the same example as above, if you replaced that power supply with a unit with 80% efficiency you would be pulling only 312.5 W from the wall, thus saving 37.5 W. If you use your computer a lot (for instance, during the whole day, every day), this savings are noticeable and at the end it pays off buying a power supply with higher efficiency, even if it initially costs a little bit more.

The second advantage is less heat being produced. In our first example the power supply would be converting 100 W into heat, while on our second example the heat dissipation would drop to 62.5 W, a 37.5% decrease in heat dissipation. This is really nice and it is always good to keep our computers running as cool as we can.

If you see a typical efficiency curve you will notice that efficiency varies according to the power being delivered and usually the power supply achieves its highest efficiency when delivering between 40% and 60% of its maximum capacity. Efficiency is also higher when the power supply is operating at 220 V. See Figure 31 for a real example.

Efficiency Curve
click to enlarge
Figure 31: Example of an efficiency curve.

Because of this effect it is recommended that you buy a power supply with double the power you are actually going to pull. This explains the offer of high-wattage power supplies above 700 W. Manufacturers don’t expect you to pull the full power from their units, but that you operate them around 50% load for a higher efficiency (during our reviews, however, we need to see if the power supply can really deliver its labeled power, because if a power supply is labeled as, let’s say, 600 W unit, we want to be capable of pulling 600 W from it, if we want to). The only disadvantage to this approach is the price of a higher wattage unit. But at the long run it is a good idea, as you will save money on your electricity bill, you computer will run cooler, you have enough headroom for a future upgrade and you won’t face any stability problems when playing games at their maximum quality for hours. As we mentioned you will be surprised that most systems will require a power supply with less than 450 W, even with our adjustment.

Read our Understanding the 80 Plus Certification to learn more about the 80 Plus efficiency certification.

Pages (14): « 1 2 3 4 5 6 7 8 [9] 10 11 12 13 14 »
Print Version | Send to Friend | | Bookmark Article | Comments (11)

Related Content
  • Seventeam ST-620PAF Power Supply Review
  • Antec TruePower New 750 W (TP-750) Power Supply Review
  • Corsair HX750W Power Supply Review
  • Thermaltake Toughpower XT 750 W Power Supply Review
  • Antec Basiq BP500U Power Supply Review

  • Recommended Deal.
    Purepower 500W Power Supply W0100 500-Watt ATX 12VThermaltake Purepower W0100RU 500W ATX 12V 2.0 Power Supply - Retail


    Newegg: $59.99 CDW: $75.99
    Directron: $54.99 CircuitCity: $59.99

    RSSLatest News
    Spire Announces CoolNess Laptop Cooler
    November 6, 2009 - 3:07 PM PST
    Mushkin Launches Memories with Copper-made Heatsink
    November 5, 2009 - 3:49 PM PST
    Super Talent Launches USB 3.0 Flash Memories
    November 5, 2009 - 3:47 PM PST
    VIA Announces Nano 3000 Processor Series
    November 5, 2009 - 3:42 PM PST
    Sapphire Announces Vapor-X HD 5870 and HD 5750 Video Cards
    November 5, 2009 - 3:38 PM PST
    Gelid Unveils Tranquillo CPU Cooler
    November 5, 2009 - 3:36 PM PST
    Noctua Intros NH-D14 Premium CPU Cooler
    November 3, 2009 - 8:14 PM PST
    Transcend Unveils DDR3-1333 Memory Kits
    November 3, 2009 - 7:57 PM PST
    EVGA Launches GeForce GTX 275 CO-OP PhysX Edition
    November 3, 2009 - 7:51 PM PST
    Akasa Launches Freedom Xone Mid-tower Case
    November 2, 2009 - 6:05 PM PST
    .:: More News ::.

    RSSLatest Content
    SilverStone Grandia GD04 Case Review
    Can We Trust the 80 Plus Certification?
    NZXT Gamma Case Review
    Patriot Box Office Media Player Review
    ASUS U-75HA 750 W Power Supply Review
    MSI P55-GD80 Motherboard
    Thermaltake Element V Case Review
    Nokia 7705 Twist Cell Phone Review
    Cooler Master Hyper TX3 CPU Cooler Review
    Some Pictures from Our Office
    Antec Two Hundred Case Review
    Corsair TX950W Power Supply Review
    XFX Radeon HD 5770 Video Card Review
    XFX Radeon HD 5750 Video Card Review
    Scythe Big Shuriken CPU Cooler Review

    Our Most Popular Articles
    Maximum CPU Temperature
    1,070,358 views
    How to Find Out Your Motherboard Manufacturer and Model
    694,578 views
    nVidia Chips Comparison Table
    671,142 views
    Connecting Two PCs Using a USB-USB Cable
    585,448 views
    How To Correctly Apply Thermal Grease
    555,673 views
    AMD ATI Chips Comparison Table
    553,915 views
    ATI Radeon X1300 Pro Review
    485,717 views
    ATI Radeon X1600 XT Review
    474,746 views
    How To Perform a BIOS Upgrade
    389,114 views
    Sempron vs. Athlon XP
    336,474 views

    Latest Threads in Our Forums
    Is it a vga problem or motherboard has shocked?
    by ftomsuk
    Patriot Box Office Media Player Review
    by cchjde
    Is it possible LCD Monitor leaked by itself ?
    by delta32
    Suddenly death syndrome and pendrives
    by Desert Fox
    better cpu cooler?
    by sam_wade07
    Video Transfer camcorder to PC
    by fjs559
    Spire Announces CoolNess Laptop Cooler
    by Hardware Secrets Team
    Can We Trust the 80 Plus Certification?
    by Merman
    SilverStone Grandia GD04 Case Review
    by Olle P
    Understanding Over Current Protection
    by Olle P
    .:: Visit Our Forums ::.


    © 2004-9, Hardware Secrets, LLC. All rights reserved.
    Advertising | Legal Information | Privacy Policy
    All times are Pacific Standard Time (PST, GMT -08:00)