Mediadevices power reduction quest Pt. 3: Appendices and conclusion
Besides the odd PC or networked media player, there’s usually more equipment silently running in the background. All these independent devices combined use up more energy then you might think. And to my surprise, one device, supposed to reduce power consumption, was actually doing the exact opposite.
USB connected NAS
My main router is a Linksys E4200 V2. Great signal range, very stable, adequate tool set and it provides a USB input to turn a USB hard drive into Network Attached Storage. One major advantage the V2 has over the V1 is it’s improved read/write speed for the USB connected storage. The NAS’ intended use was for backups, but the increased networking speed meant it was way faster compared to my PopcornHour C200 (22 MB/s vs 13 MB/s). It quickly became the repository for files I needed fast access to. Tasks like browsing through photos over the network can be painstakingly slow with the C200 but doable from the E4200’s NAS. For streaming purposes the PopcornHour was still fine though.
The E4200 has one disadvantage; it doesn’t allow the USB drive to power down. No power management whatsoever. We’ve seen in part 2 a spinning vs. an inactive hard drive doesn’t necessarally mean a large drop in power consumption, but it always helps. More important, an extra USB drive means the use yet another separate power supply.
A power supply will never be 100% efficient. This inefficiency means heat production and current leakage. So part of the overall energy is lost. Because of this, it’s better to connect multiple devices to a single larger power supply instead of using a separate one for every single device. Unfortunately, that’s not always an option. For example, the maximum current a USB 2.0 port can provide is limited to usually 500 mA (at 5 volts, so just 2,5 W). That’s nowhere near enough for most USB hard drives. Enough talk. Out comes my Fluke 87 multimeter. The power used by this secondary NAS? 74 milli amps (= 17 watts or 149 kWh a year). Not that much on it’s own, but it adds to the bigger picture.
Master-slave power socket
In an earlier attempt to save some energy, I purchased a master-slave power socket. For you who don’t know what that is; it’s an extension socket with one master and several slave outlets. Plug your main device, e.g. a PC, into the master and peripherals you tend to use together with the PC into the ‘slaves’. Once turned on, the power used by the PC passes a certain threshold pre set in the socket which in turn switches on the slave outlets, powering all ‘slave devices’. If the PC turns off, the power falls below the threshold and all peripherals plugged into the slave outlets are completely shut off, effectively eliminating standby currents from adapters and other inefficient power supplies, saving you a few watts.
But here’s the thing. The socket itself uses energy for it’s internal circuitry too. A whopping 16 watts of power! In my case 12 watts more then the standby power leakage of all slave devices combined! It seemed a perfect solution, but ended up doing the exact opposite of it’s intended purpose. I immediately replaced it for a normal switched extension socket. Another annual saving of 105 kWh.
Let’s add it all up
I tried to give a picture of the devices, their role and their power consumption, I use on a daily basis for all my multi media needs. At home, at work or on the road. On my main TV set and streaming to multiple iOS devices over my LAN of WAN. Here they are again with their idle power usage:
- PLEX server PC: 51 W
- PopcornHout C200: 42 W
- Secondary NAS: 17 W
- Backwards Master-Slave socket: 12 W (usage minus savings)
Added up, that’s 122 watts of continues use which means 1068 kWh annually or, at 22 cents per kWh, the total sum of 235 euros.
So… what to do about it
Those of you who’ve read part 1 and part 2 might have guessed; I ordered a Mac Mini. Currently on sale for 499,- euros. The specs state it will only use 11 watts when idle (with Finder open as Apple likes to put it). I will need to connect an additional hard drive to it to house all of my files. But because of the Mac’s power management features, it will use less power then it does connected to my E4200. I estimate the setup will use an average of 20 watts. That’s 175 kWh (38,55 euros) a year. A difference of 893 kWh or better yet, 196,45 euros! The Mac Mini will earn itself back in a little over 2,5 years, not to mention the extra functionality compared to the PopcornHour C200 and it’s resale value once I inevitably switch over to another toy.
Stay tuned for my articles on how I turn a Mac Mini into a proper media center.