Efficient Computing
Step 1: Efficient Servers
A sustainable infrastructure starts with making our computers use as little electricity as possible. Most of our machines are servers, high-performance computers that run all the time. Defining and measuring the overall energy efficiency of a server is harder than it is for appliances such as washing machines, refrigerators, or air conditioners because servers run different applications unlike appliances that perform a single function. Therefore, we rate the efficiency of our servers by measuring the power used by each of the actual computing elements (such as processors and memory) against the power used by all other things (like fans and power conversion).
Up to a third of the total energy consumed by a typical server is wasted before reaching the computing components. The majority of these losses occur when converting electricity from one kind to another. The power supply, which converts the AC voltage coming from a standard outlet to a set of low DC voltages, is where most of the energy is lost. A second major source of wasted energy is in voltage regulator circuitry. This circuitry sits on the computer's motherboard and further converts the power supply's output voltages to the voltages required by the microchips. Both sources have traditionally been designed with low efficiency standards to save a few dollars on initial cost. However, this inefficiency causes the owner to spend many more dollars on electricity usage down the road. (So if you're about to buy a new server or computer, buy an efficient one!)
Google servers are different. In 2000 we began our focus on efficient power conversion and for many years now we've used power supplies (pdf) that exceed the Climate Saver Computing Initiative's "Gold" efficiency standards. Similarly, our motherboards use very efficient voltage regulator modules, maximizing the amount of electricity delivered to the components that do work. Our servers only lose a little over 15% of the electricity they pull from the wall during these power conversion steps, less than half of what is lost in a typical server. Efficient power conversion pays real dividends; we estimate an annual savings of over 500 kWh per server over a typical system.
Additionally, we omit parts that aren't needed for our applications. For example, our servers don't have any graphics chips. We also optimize our servers and racks to use the minimum amount of fan power possible. Moreover the fans are controlled to spin only as fast as necessary to keep the server temperature below a threshold. We encourage all of our suppliers to produce components that operate efficiently whether they are idle, operating at full capacity, or at lower usage levels, a property we call "energy proportionality." Our published studies indicate that more energy proportional systems could cut in half the total energy used by large data center operations. Altogether, we're confident that our servers are among the most efficient systems ever deployed.