Efficiency has become a purchasing criterion in this industry, and I would like to be generous about why, but the honest answer is that a large number of people ran out of electricity.
Not ran short. Ran out. There is a specific and increasingly common conversation in which somebody wants to add machines to a facility, and the constraint turns out not to be floor space or money or cooling capacity but the size of the feed coming in from the utility. That number is fixed. Changing it means the electricity company, and a project measured in years.
Once you hit that wall, every question changes shape. The question is no longer how much performance you can buy. It is how much performance you can extract from a watt you already have, because watts are the thing you cannot get more of.
This explains a lot of behaviour that otherwise looks like environmental positioning. It is why the large operators are putting buildings next to hydroelectric dams in Oregon and Washington, which have no particular advantage in land, labour, or proximity to customers. They have power, and cold water, and those are now the scarce inputs.
It is also, I suspect, most of the real story behind server consolidation. I wrote last month about the industry using virtualisation to route around a concurrency problem it could not solve, and that holds. But the thing making the sale is simpler than either the technical argument or the cost argument. A machine idling at eight percent utilisation still draws most of the power of a busy one. Twenty of those consume a feed you cannot expand, doing almost nothing with it. Collapsing them into three is not primarily about saving hardware money. It is about getting capacity back that you had already paid for and were burning.
On the consumer side none of this applies and nobody should pretend otherwise. There is a certification scheme for power supplies now, most people have never heard of it, and the ones who have do not check. A power supply’s efficiency is invisible, the saving is a few dollars a year, and nobody has ever chosen a computer that way.
Laptops are the exception, and only because efficiency there is not called efficiency. It is called battery life, which is the same physics wearing a name people care about. A processor that draws less is a machine that lasts through a flight, and that sells.
Which is roughly the rule. Efficiency gets adopted wherever it has been renamed as something the buyer actually wants, and ignored wherever it is presented as a virtue.