June 15, 2024

Monitoring all the electrical and hydraulic appliances in your house

Dan Wallach recently wrote about his smart electric meter, which keeps track of the second-by-second current draw of his whole house. But what he might like to know is, exactly what appliance is on at what time? How could you measure that?

You might think that one would have to instrument each different circuit at the breaker box, or every individual electric plug at the outlet. This would be expensive, not particularly for all the little sensors but for the labor of an electrician to install everything.

Recent “gee whiz” research by Professor Shwetak Patel‘s group at the University of Washington provides a really elegant solution. Every appliance you own–your refrigerator, your flat-screen TV, your toaster–has a different “electrical noise signature” that it draws from the wires in your house. When you turn it on, this signal is (inadvertently) sent through the electric wires to the circuit-breaker box. It’s not necessary (as one commenter suggested) to buy “smart appliances” that send purpose-designed on-off signals; your “dumb” appliances already send their own noise signatures.

Patel’s group built a device that you plug in to an electrical outlet, which figures out when your appliances are turning on and off. The device is equipped with a database of common signatures (it can tell one brand of TV from another!) and with machine-learning algorithms that figure out the unique characteristics of your particular devices (if you have two “identical” Toshiba TVs, it can tell them apart!). Patel’s device could be an extremely useful “green technology” to help consumers painlessly reduce their electricity consumption.

Patel can do the same trick on your water pipes. Each toilet flush or shower faucet naturally sends a different acoustic pressure signal, and a single sensor can monitor all your devices.

Of course, in addition to the “green” advantages of this technology, there are privacy implications. Even without your consent, the electric company and the water company are permitted to continuously measure your use of electricity and water; taken to the extreme, this monitoring alone could tell them exactly when you use each and every device in your house.

Smart electrical meters and their smart peripherals

When I was a college undergraduate, I lived in a 1920’s duplex and I recall my roommate and I trying to figure out where our electrical bill was going. He was standing outside by the electrical meter, I was turning things on and off, and we were yelling back and forth so we could sort out which gadgets were causing the wheel to spin faster. (The big power sinks? Our ancient 1950’s refrigerator and my massive-for-the-day 20-inch computer monitor.) Needless to say, this was more difficult than it should have been.

More recently, I got myself a Kill-a-Watt inline power meter which you can use at any power outlet, but it’s a pain. You have to unplug something to measure its usage. People with the big bucks will spring for a Ted 5000 system, which an electrician installs in your breaker box. That’s fantastic, but it’s not cheap or easy.

Today, I’m now the proud new owner of an LS Research “RateSaver”, which speaks ZigBee wireless to the “smart meter” that CenterPoint Energy installed on all the houses in our area. How did I get this thing? I went to a League of Women Voters “meet the candidates” event back in October and CenterPoint Energy had a display there. I asked the guy if I could get one of these things and he said he’s look into it for me. Fast forward two months later, and a box arrived in the mail. New toy!

So what exactly is it? It’s a battery-powered light-weight box with a tolerably readable two-inch monochrome LCD display. As I’m sitting here typing, it’s updating my “current usage” every few seconds and is giving me a number that’s ostensibly accurate to the watt. In the last minute, after I pressed the proper button, it’s been alternating between reading 650-750 watts, and 1400-1500 watts. (Hmm… maybe my fridge consumes 700 watts.) If you leave it alone, the refresh rate slows down to maybe once a minute. Also, it’s sometimes reading “0.000 kW” which is clearly incorrect but it returns to the proper number when I press the button. Wireless range is quite good. I’m on the opposite side of the house as our electrical meter and it’s working fine.

The user interface is all kinds of terrible. In addition to slow button response, the button labels are incorrect. LS Research is apparently just rebranding a Honeywell Home Energy Display (for which the Honeywell manual was included). LS Research apparently rearranged the button labels without changing the corrresponding software. Bravo! Thankfully, the Honeywell manuals have the proper labeling. Also amusing: there’s a message in the system saying that “non-peak price starts at 7:00 PM. Save Money by waiting” when in fact my electrical pricing deal is for a flat rate (which floats with market conditions and is presently $0.0631 per kWh).

Update: I’ve since learned that Honeywell acquired LS Research, so this is something of a transitional screw-up. Welcome to the world of beta products.

Since I’m a security guy, I assumed I’d have to go through some kind of protocol to get the thing activated, and the manual from inside the box describes an activation procedure where you make a phone call to your energy company, giving them the hardware ID numbers of the outdoor smart meter and the indoor display box. Conflicting instructions were also included with my display, describing setup which was as simple as “turn it on and hit the connect button” so I went with the easy instructions. Time passed and the box started working without requiring any additional input from me. I hope that my display box was pre-configured to work exclusively with my house, but this does lead me to wonder about whether they got the security right. (I experimentally turned lights on and off while watching the meter updates and validated that I am, in fact, looking at the usage of my own house.)

At the end of the day, I and everybody else here is now required to pay a $3.24 “advanced meter charge” in order to have all this functionality (which, incidentally, saves the electric company money since it no longer needs human meter readers). Is it worth it? Presumably, at some point I’ll have some kind of variable-priced electricity and I could then hack my refrigerator and air conditioning system to pay attention to the spot price of electricity. If electricity got extra cheap during a five minute window of the hot summer, the controller could then crank the A/C and drop the house an extra few degrees. Of course, if everybody was following this same algorithm, you’d either have insane demand swings, when everybody jumps on to consume cheaper electricity when it’s available, or you’d have to carefully engineer the pricing system such that you had stable demand. Presumably, if you got somebody who understood control theory to design this properly, you could end up incentivizing both demand and pricing to be fairly stable across the space of any given hour of the day.

Probably the biggest benefit of these smart meters will come the next time we have a major hurricane that comes through and knocks out power. Hurricane Ike left my house without power for ten days. At the time, CenterPoint Energy had a vague and useless web site that would give you an idea what neighborhoods were being repaired. Since it was too hot to stay in our house, we stayed instead with a friend who had power and drove by our place every day to see if it had power. This was very frustrating. (I unplugged all my computer equipment, since I didn’t want flakey power to nuke my equipment. Consequently, I couldn’t just do something simple like ping my home computer.) Today, I can log into CenterPoint Energy’s web site and see the power consumption of my house, in 15-minute intervals, and so can the people coordinating the repairs. If they integrated that with a mapping system, they’d have real-time blackout maps, which have obvious value to emergency planners and repair operations coordination.

I just hope they have somebody with a clue looking over the security of their system. (If somebody from CenterPoint reads this: people like me are more than happy to do private security evaluations, red-team exercises, and so forth.)

Future work: there’s a mini USB port on the side of the box. Now I just have to find some documentation. It’s probably bad form for me to go reverse-engineer it myself.