Impact of Virtual Machines on Idle Mode Power Consumption

Ever since I discovered the benefits of running Virtual Machines on my notebook for a variety of things and how easy it is in practice I usually have three of them running at the same time. Yes, three of them at the same time and with 8 GB of RAM and using Ubuntu as host operating system makes the experience quite seamless.

A second Ubuntu is usually running in one virtual machine so I can quickly try out things, install programs I only need for a short time and don't want to linger around on my system and to run a TORified Firefox against unfriendly eavesdropping of half the world's security services. Also, by disabling the virtual network adapter and mapping a 3G USB stick or USB Wi-Fi stick directly into the virtual machine gives me a completely separated and independent second computer. Great for networking experiments. The other two machines usually run an instance of Windows XP or Windows 7 for programs that aren't natively available under Linux. There aren't a lot of those but they do exist. As the VMs are usually not in the way I usually start them but never terminate them unless I need to reboot the host. The only thing I noticed is that there is a power consumption impact.

When I was recently taking a long train trip I noticed that the remaining operation time indicated in the status bar was about one hour longer than usual. I was puzzled at first but soon noticed that the difference is that I had just rebooted the day before and I didn't have the need for a VM running since. It's obvious that VMs have an idle power consumption impact because instead of one OS there are usually four operating systems performing their background operations during idle times on my notebook. So while I was surprised I really shouldn't have been. But the takeaway from this is that in the future I know of a good way to increase the autonomy time in case I need it.