performanceperwatt

Performance per watt, also known as efficiency, is a metric for evaluating how much computational performance a system delivers per unit of electrical power consumed. It is commonly expressed as operations per second per watt, such as GFLOPS per watt or MIPS per watt, depending on the performance measure used.

Because different workloads place different demands on hardware, the reported value depends on the benchmark and workload. Peak theoretical performance may differ from sustained performance under realistic usage, and system-level power includes components beyond the CPU or accelerator.

In computing, perf/W is central to green computing, data-center design, and high-performance computing. The Green500 list ranks HPC systems by FLOPS per watt, while benchmarks such as SPECpower_ssj assess server efficiency across typical operating conditions.

Improvements in perf/W come from multiple sources: dynamic voltage and frequency scaling, advanced cooling and power management, architectural innovations (vector units, deeper caches), fabrication process advances, and the use of specialized accelerators (GPUs, AI chips).

Critics caution that perf/W alone may be misleading if not aligned with performance requirements or total cost of ownership. High efficiency can trade off latency, reliability, or peak performance, and measurements may vary with test conditions and workload mix.

Related concepts include energy efficiency, power management, and energy proportionality. Performance-per-watt analysis informs chip design, data-center planning, and device selection as part of broader considerations of total cost of ownership and environmental impact.