Sometimes I try to squeeze more battery time from my old laptop, and I look for processes hogging the cpu. Invariably I see Firefox consuming 30-40% cpus and I have to hunt down those misbihaving tabs that, even idle, keep the cpu awake.<p>The reality is that today saving power matters everywhere. On mobile and laptops means a longer lasting battery and&#x2F;or lighter device; on a desktop and laptop it means a quieter machine; on the datacenter, power usage is probably the  most important cost today.