How much electrical power does a virtual machine use?

Question

I recently received an email from my employer indicating that for 'environmental reasons' they will be shutting down Windows virtual desktop machines if they're idle for more than eight hours. I was wondering, assuming that the organisation had capacity for 1000 virtual machines, what would be the power saving (Watts) by shutting down a single idle virtual machine? How would this compare, as a percentage per physical machine, to simply encouraging staff to turn off their physical laptop overnight instead?

PragmaticPulp · Accepted Answer

We need to know more about where and how they’re hosted.
I have my VM server plugged into a watt meter. Launching a single additional VM (qemu) doesn’t change idle power consumption in a measurable way.
However, if they had 1000s of idle VMs then they’d need to keep additional servers running because a single server can only host so many VMs, idle or not.
I’d guess this is more about limiting their hardware spend than actually saving significant amounts of energy. A single employee commuting to the office in a car consumes far more energy than an idle VM running for a long time.

1970-01-01 · Answer

Ask them for data, not HN. Power consumption is something that can easily be calculated and measured, however assumptions will have to be made that almost certainly will not be accurate for your employer.

sarcasmatwork · Answer

Maybe resource reasons.. 'environmental reasons' is someone that does not understand VM's.