Cutting power costs with Raspberry Pi

Much of my free time the past few months has been dedicated to moving various services and infrastructure out of my apartment. Where possible I've also been in search of solutions that are free (or at least really cheap).

I've known for a while my initial goal of removing all local infrastructure just wasn't feasible. For services that just weren't practical to host elsewhere, my goal was to find a way to reduce cost, noise, and maintenance. Let me set the stage...

The Old Set Up

Galactica in all its glory.
My old set up is a combination of old gaming rigs I had built over the years. There actually isn't anything special about it. It's not particularly powerful or reliable, and it's really loud.

It runs KVM with a fancy WebVirtMgr interface for easy administration. At this point, however, I've removed all services from it with the exception of a proxy server, Plex media server, and web server.

The Idea

While the KVM box isn't super powerful it does consume a non-trivial amount of electricity. I don't have any plans to change my internet subscription so the only real way I can reduce the cost of hosting services is to focus on power.

Services like my proxy and web server get little to no traffic but are things that I like to keep active at all times. Keeping in mind their lack of use they seemed like good candidates to move to a platform that draws less power. Having recently started playing with a Raspberry Pi B+ this was a natural place to start. The real question was whether or not I could get a Plex media server up and running on a Pi.

The Investment

While the ultimate goal was to save money on my electric bills I also didn't want to come up with a solution that cost more than I could re-coop within a year(ish). With that being said here's the bill for my new set up:

*I had one sitting around

All in all I'm in ~$120 for this particular project. There are a number of factors that could make this number lower. For example, Pi cases aren't necessary, you could find smaller/cheaper MicroSD cards, and the Pi 2 B is the top of the offerings (you could get a Pi 1 B+ for at least the proxy/web stuff). I expect you could produce similar results on a tighter budget (~$80).

The Results

I've now got two Pis up and running. One is handling my proxy and web traffic while the other is a Plex media server (which I'll probably do a separate post on). Now for the fun stuff.

Galactica (KVM)

State Power Consumption
Boot 149W (Peak)
Idle 91.5-95W

PlexPi

State Power Consumption
Boot 5.9W (Peak)
Idle 4.9-5.3W
Load 6.5W (Peak)

WebPi

State Power Consumption
Boot 2.4W (Peak)
Idle 1.7-1.9W
Load 2.3W (Peak)

For a more conservative estimate of my savings I based my calculations on the lower idle consumption of Galactica and split the difference between the higher idle consumption and load consumption of each Pi. My last electricity bill came back at $.113 per kWh. Going on those assumptions here are the cost break downs:

Device Average Consumption kWh Per Year Cost Per Year
Galactica 91.5W 801.54 $90.57
PlexPi 5.9W 51.684 $5.84
WebPi 2.1W 18.396 $2.08

It's actually cheaper to run my dual Pi set up than for me to keep our Keurig plugged in (and off). Even with a very conservative estimate and only comparing against idle consumption on the old KVM box I'm saving over $82 a year. I didn't quite hit my goal of paying the hardware off in one year, but I'm still quite happy with the results.

PlexPi. Velcroed to the wall in my closet

~MJ

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