Low-power ICs and low-power designs are hot these days (of course, we are only speaking figuratively here, not literally). This is not just for "environmental/green" reasons, although that plays a part in it. The simple fact is that low-power designs enable longer product run times from a given battery pack. Even when you are not source-limited and have an AC line in your product, lower power translates into cooler products, which simplifies thermal issues and increases reliability, and has many other system-level benefits as well.

But how do you achieve low-power results? This does not always have a simple answer. The obvious approach is to use lower-power ICs, higher-value resistors (if you can; lower current = less I²R loss), and other parts which minimize dissipation.

Sometimes, though, the simple approach is also too simple, and the sum of the parts is not enough to yield the results you need. It may turn out that a higher-dissipation part has better functionality for the project, or has better power-management and sleep-mode operation. Depending on your duty cycle and peak/average/quiescent power needs, a higher-dissipation part may actually reduce overall consumption. Or, you may have an audio amplifier with good efficiency at moderate audio volume, but lower efficiency at the audio levels users will actually use it.

As with most engineering and design issues, there is no single, simple answer, and judging the tradeoffs is an important part of the challenge. Don't rush to the obvious answer, until you take a little while to think about the question from different angles.♦