Energy Star Label

Robert Horn <rjh at> wrote: "

I had a chance to discuss Energy Star with the designers of desktop printers. They confirmed that the allowable stand-by power targets depend on the device, and they only knew their targets. But they made some other interesting comments:

  • Energy Star ratings lead to significant operational power savings. Timer based power savings are the exception. Most savings come from designing in power on demand with low leakage drivers. For example, using stepper motors with low leakage current instead of high leakage.

    This savings is both from individual designs and from the resulting demand for low leakage products causing better and cheaper low leakage product designs. The old-style (e.g. typewriter) design with one motor (always on) and various clutches is no longer the least cost.

  • Energy Star was good organizational engineering. It never required designers to compromise quality or performance, which made it much harder to argue against design changes to reduce power consumption while idle. Since most of the savings begin the millisecond that parts stop moving, these savings are considerable.

  • The power ratings on PC's are a safety rating, not a usage rating. So the 235W and 300W power supplies that commonly found in PCs are specifying their safety limits. Actual full power usage is much less, typically 20-30 percent of the safe limit. The designers also noted that it is actually difficult to measure the power consumption of a switching power supply. You need to use specially designed power meters. The regular AC meters are designed for motors, and are rather inaccurate for switching power supplies.