Bottom Line Up Front - I saved $177 per year on 'standby' power with one Z-wave Switch.
My quest for figuring out where all of my electricity is being used continues. In this article we'll again employ the trusty Aeotec Smart Switch 6 for monitoring power usage and couple that with Emoncms, an open-source web-app for processing, logging and visualising energy, temperature and other environmental data.
I go into more detail on how to get Emoncms working with Vera in another article. For now I'll focus on identifying where power is being wasted and how to reduce it - in this example in the Home Theatre where devices spend a lot of time in standby when you're not binge watching the latest season of Game of Thrones.
Step 1 - Baseline Graph
This is a matter of putting the Aeotec Smart Switch into the wall, and connecting all of the powerboards to it. Now all of my theatre devices can be monitored for total power use. Given that we're going to be continuously logging data, you want to change some of the Device Options so that it continually updates, rather than sending updates only when the power use changes by 25W or 5% (defaults).I set mine to update every 30 seconds in a single report group and disable the delta function entirely.
I then created a free account for my Vera on Emoncms.org, added some code to my Startup Lua to send data every 60 seconds and went about my usual business for a couple of days.
Step 2 - Interpreting the Results
Logging into Emoncms I was able to quickly produce a time series graph of the power usage in my Home Theatre.
Right, so when that room is not in use I could see that it's using around 100W of power costing $236 per year. I wasn't seeing the value in that expense considering I could be spending it on something else, like beer. The question then becomes what's using it, and can I reduce it?
Step 3 - Separate Essential from Non-Essential Power
I have a few devices in my Home Theatre that need to be on all the time. My gut told me that there's no way they should be using 100W of power.
Essential - Run all the time
- ASUS ADSL Router
- 2 x Vera Automation Controllers
- Network Switch
- Philips Hue Hub
- Raspberry Pi
Non-Essential: Needed only when watching movie
- Sony Home Theatre Receiver
- Popcorn Hour Network Media Player
- Sony DVD Player
- Sony Set Top Box
- Telstra TV (Roku)
- Epson Projector
I put each of these groups of devices on a separate powerboard, and in turn connected them to my Aeotec Smart Switch and checked the results.
- Essential Power: 25W / $59 per year.
- Non-Essential Power (Standby): 75W / $177 per year.
And there is the size of the prize - $177 annual electricity cost for no value to me whatsoever. At the going rate at my local microbrewery, that's about 50 litres of Trav's excellent Ocean Ale.
At this point, you could finish there and say it's just a matter of leaving the Z-wave switch in place and turn it off from your smartphone when you're done with the movie. But this is a home automation blog and we're not about creating manual tasks.
Step 4 - Make it so you don't have to do anything different
This is how you lock in the savings, don't rely on people to remember anything, they are inherently unreliable.
You could use a motion sensor to detect when the room has been vacated and shut the Non-Essential Power off. Of course I can foresee a situation where everyone is sitting really still and suddenly the screen goes black. This is not good for the WAF (Wife Acceptance Factor) and will get the funding for your Home Automation Projects canned real quick - trust me on this.
There's also a risk if you have a projector where you shut off the mains power before the fan has had an opportunity to cool the globe down. This applied to me so I neither wanted Vera arbitrarily shutting off the power nor requiring someone to press a button which they would either forget about or potentially press before the projector had correctly shut down.
Fortunately, in my Home Theatre I have an iPad running iRule which I use to control all of my AV devices and the lights which are connected to Vera.
iRule allows for macros and commands to be executed on button presses - as I already had buttons for starting up the theatre (and shutting it down) it was just a matter of incorporating the Non-Essential Power Z-wave switch into those macros.
First up I created 2 manually activated scenes on Vera. One just immediately activated the Non-Essential Power Z-wave switch and the other to shut it down after a 2 minute delay. This delay gives the AV devices the opportunity to complete any standby/shutdown activities before the power is switched off.
On iRule, each of those buttons to incorporate HTTP commands for Vera to activate those scenes while it's turning on/off the AV devices. In the Vera Module, add a Network Code which has a data property like:
Handy tip here - just about everything on Vera can be manipulated via HTTP commands meaning you can do all sorts of integrations with other apps or websites.
Step 5 - Results
The chart pretty much speaks for itself.
Standby power consumption is now ZERO on the AV gear and I'm not having to even think about managing that standby power. Vera takes care of it and I just pocket the savings.
If you have a Vera already, this is a no brainer project.
- Total Investment - $89
- Total Annual Saving - $177
- Payback Period - 6 months
Even if you have to buy a Vera, it's still a 2 year payback and it opens up other opportunities as well.
For example - The Xbox in the games room uses about 20W / $47 per year of power in standby. I'm going put it on a Z-wave switch that turns on/off based on whether or not the kids are home. That way when they're here to use it, it'll be ready to go and able to download updates. It'll also allow Luisa to enforce the "No Xbox until homework is done" rule, even when she's not at home.
See what I did there? Always consider the WAF.
The follow up to this article, where we implement an ECO Pool Pump is here.
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