Rising energy costs and environmental concerns have raised awareness of opportunities to conserve and reduce electricity used by Information Technology equipment, especially computers. Computer power management software and power supply efficiency are key elements in the drive to conserve energy resources. Before examining these elements let's go over a basic primer on power supplies and the computers they run.

A computer power supply outputs several steady DC voltages. Each voltage has a minimum and maximum allowable current range. Computer devices draw variable current from one or more of the steady DC voltages. Since Power = Voltage x Current, and voltage is always constant, it's easy to see power usage is highly dependent on the computer's current draw. Also, another basic point is the power supply must always be able to supply the maximum current required. The computer should use power only when necessary. The power supply should deliver the power in an efficient manner.

The role of power management software is to determine when a computer device, such as a hard drive, is doing useful work or not. If the device is detected as inactive it can be placed in a low power standby or sleep state, substantially lowering or eliminating current draw. This software also provides the ability to create power schemes, trading high system performance for lower power consumption. All major operating systems, such as Microsoft XP, have built in power management software based on Intel's ACPI (Advanced Configuration and Power Interface) specification. ACPI allows operating system control of device power states.

Computer power supply efficiency is a more direct, measurable, and tangible target for conservation. Power supplies are energy conversion devices. They convert the AC input into DC outputs required by computer circuitry and peripherals. During this conversion, a certain amount of energy is lost as heat. This heat loss determines power supply efficiency. Typical efficiency is 70%, in general very good by energy conversion standards. It is worth noting computer power supplies are a class known as switching power supplies, inherently more robust and efficient, than their linear power supply counterparts.

However, there is room for improvement and given the vast number of computer power supplies in service, the savings could be huge. It is estimated office computers consume over 320kwh (kiloWatt Hours) per year. Improving efficiency to 80% results in savings of approximately 45kwh per year. Electric utilities are eager to capture this savings and have formed the 80PLUS Program. 80PLUS aims to integrate more energy efficient power supplies into desktop and server computers. The ENERGY STAR computer specification now includes 80PLUS power supply efficiency rating. 80PLUS has gained wide acceptance with leading power supply manufacturers, OEMs, and consumers.

The 80% or greater criteria must be maintained at 20%, 50% and 100% of rated load. Power supplies typically become more efficient as the load is increased. The 20/50/100 rule ensures consistent efficiency as loads go up and down.

Why 80% ? Would not a minimum of 90% be even better and generate more savings ? The answer, when considering total ownership costs, is no.

The reason has to do with existing power supply design and production. Computer power supply manufacturers are under extreme price pressure from OEMs and consumers. Even a 50-cent price increase can cause significant customer defection and consternation. Inexpensive analog components are used to manufacture today's computer power supplies. Capacitors, Inductors, Resistors, and Transformers. These components are complimented by a two power transistors and control circuitry. Combined with cheap labor and 24/7 factory volume, prices are driven down to quite astonishing levels, at least by Western standards. 80% is around the maximum efficiency that can be obtained from this analog switching power supply design. A move to 90% would require expensive DC to DC modules produced by companies like Vicor.

80PLUS gives the best power supply companies an opportunity to distinguish their products in a crowded marketplace. Where to buy ? For starters, right here at Power-On. We carry Fortron/Source and Seasonic, #1 and #2 in number of 80PLUS certified power supplies. Both have been manufacturing superior power products for a long time.