Why Are Efficiency Measures So Important?

Two years ago, we conducted a live stress test between an AMD and an Intel system, which measured the power consumption of both systems (among other things). At full or peak load, we measured average gross power consumption at 342 Watts on the Intel system, which included a dual core Intel Pentium Extreme Edition 840, a Gigabyte GA-8N-SLI Royal motherboard, OCZ DDR2 DIMMs, two GeForce 6800GT graphics cards in an SLI configuration, and two 160 GB 7,200 RPM Western Digital hard disks. Following the recommendations of the Power Supply Design Guide that the PSU be 77% efficient at peak load, the average power output from the device was around 263 Watts. One of the consequences of this test was that nearly 80 watts of energy was transformed into waste heat, adding significantly to operating costs for energy.

Let's restate this in plain terms: when it comes to paying for power, we have to cover the costs of gross consumption. In addition, we must also get rid of the waste heat that results from lower efficiency levels, which increases the need for cooling (itself an overhead energy consumer) and increases noise levels as fan speeds go up. If the waste heat isn't expelled from the PC case, this has a negative impact on PSU lifetime, because the lifetimes of its individual components sink as temperatures rise.

Now, let's look at our power supply selection from a different perspective. Power users are less interested in lower efficiency ratings at lower loads than they are in the PSU's ability to deliver sufficient power on demand. A 1,000 W PSU that is used to deliver only 200 W of actual power consumed works best to meet demand, though users must then pay for lower efficiency levels and rising costs of electricity.

With its Odin family of PSUs, Gigabyte seeks to deliver at least 80% efficiency over the entire load range. Over time, this means that when such a device is compared to the total cost of ownership for a cheaper power supply (purchase cost plus energy costs, in other words) it produces net savings. This helps to offset the higher costs of initial purchase, but only if the vendor ratings for the device are accurate. That's why we put the Odin PSUs to the test in our labs.

Higher efficiency across the whole load range promises cost savings.