How Tweet-a-Watt Works

The power meter Kill A Watt is the basis behind the Tweet-A-Watt gadget.
The power meter Kill A Watt is the basis behind the Tweet-A-Watt gadget. See more green science pictures.
Photo courtesy of Tweet-A-Watt

If you sat at work every day watching your home power bill rise because you left your toaster plugged in that morning, do you think you might start remembering to unplug it on your way out? What if all your hiply green-minded friends were watching, too?

That's the basic idea behind a new power-monitoring gadget called Tweet-A-Watt. The device, developed by Make Magazine's Phillip Torrone and Adafruit Industries' Limor Fried, took first place in the 2009 Greener Gadgets Design Competition. It builds on an existing power meter called Kill A Watt, combining two of today's trendiest topics: energy efficiency and social networking. Tweet-A-Watt is, at the very least, a timely development.


It begins with simple power monitoring -- measuring the wattage an appliance uses by placing a watt meter (like Kill A Watt) between an appliance plug and a wall outlet (see How Kill A Watt Works to learn more). There are different approaches to power monitoring. You can track the wattage (in kilowatt-hours, or kWh) for a single appliance, for a set of appliances, for a whole room or a whole house, and different monitors output the data in varying ways. But the end goal is always the same: Know exactly how much power different electrical devices are using so you can reduce your electricity costs and your polluting, wasteful power consumption.

Tweet-A-Watt takes this concept a step further. In addition to thriftiness and guilt, the device introduces a couple of additional time-tested motivators: competition and peer pressure, via social-networking Web site Twitter.

In this article, we'll find out exactly what Tweet-A-Watt does and how it's supposed to work, and we'll look at the basic steps involved in building one. The big deal here is less the power-monitoring capability and more what you do with the information. Tweet-A-Watt puts your energy consumption out there for all the world to see. Or at least for your "followers" to see.


Tweet-A-Watt Basics

You might regret that vampire power a bit more when you start getting Tweets about it.
You might regret that vampire power a bit more when you start getting Tweets about it.
Photo courtesy of Tweet-A-Watt

If you have a Twitter account, you know what "followers" are. They're people who are signed up to receive your Twitter status updates -- important messages like "I'm going grocery shopping" or "I'm in line at the movies"-- that you send to your Twitter account via Internet-connected computer or cell phone. With Tweet-A-Watt, those Twitter followers also receive updates on your energy-consumption status. The updates are sent not by you, but by your energy monitor.

The folks behind Tweet-A-Watt believe that publication of energy consumption data will encourage both an increased sensitivity to one's own wasteful behaviors, because other people can see them, and some friendly rivalry that could get people trying to outdo each other on energy savings.


It's a pretty solid argument. People do tend to behave differently when others are watching. (How often do you pick your nose in public versus in private?) And we can just look at the Prius "hypermilers" for an example of what happens when like-minded individuals suddenly have an easy way to measure their success. Using the in-dash Prius mileage calculator, drivers have been known to achieve well beyond the car's U.S. Environmental Protection Agency (EPA) mileage rating while attempting to beat their own and their friends' mileage records [source: Washington Post].

And Tweet-A-Watt makes it even easier to share conservation results than the Prius mileage calculator, because it's Internet-connected. You don't even have to make a phone call to let your friends know you decreased your energy consumption by 10 percent over the previous day. Or that you tweaked your entertainment system and now it's more efficient than theirs. That information is delivered automatically via Twitter. It works like this:

You attach a networking device to a Kill A Watt. That device reads the energy monitor's power data and sends it wirelessly to a computer (or Internet-connected microcontroller). The computer then sends your data to Twitter for all your followers to see.

That's once you set it up, though. Tweet-A-Watt isn't an off-the-shelf gadget. It's a tweak on an off-the-shelf gadget. You have to make it yourself, with a Kill-A-Watt, some software and a few additional parts like capacitors and resistors. And be prepared -- there's soldering involved.

On the next page, we'll take a look at what you need to do to build a Tweet-A-Watt.


Build Your Own Tweet-A-Watt

You can make a Tweet-A-Watt yourself, but be prepared: There's soldering involved.
You can make a Tweet-A-Watt yourself, but be prepared: There's soldering involved.
Photo courtesy of Tweet-A-Watt

The Adafruit Web site, which sells the Tweet-A-Watt starter kit, calls Tweet-A-Watt a "moderate/advanced" project. Here's an overview of the process so you know what to expect if you want to dig in (for very detailed instructions, look at the Tweet-A-Watt Web site).



  • Kill A Watt power meter (about $20)
  • Tweet-A-Watt starter kit ($90), including two XBee wireless modules, two XBee adapters, an FTDI cable and a bunch of basic electronics parts
  • Soldering iron
  • Solder
  • Multimeter/oscilloscope
  • Flush/diagonal cutters
  • Helping Hands stand with magnifying glass
  • Sticky foam (the crafting product, not the nonlethal weapon)

Once you have everything assembled …

Building the Receiver

At this stage, you'll solder one of the XBee adapters together and then make sure each XBee module can communicate with the adapter. You'll download a piece of software (Windows-only!) to set the communication settings.

Upgrading and Configuring

Next, you'll do some software work on the XBee modules -- no hardware manipulation here. You'll upgrade the firmware on both modules and then configure the transmitter module to pull data from specific pins on the Kill A Watt, send data at certain intervals and talk to the adapter on certain channels. Again, you'll be using a piece of Windows-only software to assist you.

Building the Transmitter

To build the transmitter setup, you'll be doing a bunch of soldering, working with capacitors, resistors, wires and heat shrink. You'll also be opening the Kill A Watt case and drilling a hole in it to insert a new LED for the Tweet-A-Watt.

Running the Software

Finally, you'll set up the software to accept the energy data and publish it to your Twitter account. You'll be using a programming language called Python to make some modifications to a script and run a few commands (all fully written out for you in the instructions).

If you don't already have a Twitter account, you'll have to set one up here. Once you plug your Twitter username and password into the script, you're good to go.

This is the most basic setup: Tweeting the data from a single Kill-A-Watt. With some additional parts and programming tweaks, you can arrange the system to compile and report data from multiple outlets, so you could get a whole-home energy report going on your Twitter account if you really want to. That might get expensive, though, since the parts for each add-on outlet run about $60.

If this type of work isn't up your alley, you can probably just wait a little while and buy one pre-made. The designers made Tweet-A-Watt's plans open source, so anyone can make a commercial product out of the concept. And if Tweet-A-Watt takes off, we could start seeing lots of devices that use the power of Twitter for good.

For more information on Tweet-A-Watt and power monitoring, look over the links on the next page.


Lots More Information

Related HowStuffWorks Articles

  • Troast, Peter. "Congratulations to 'Tweet-a-Watt,' Winner of the Greener Gadgets Design Competition." Energy Circle. March 2, 2009.
  • "Tweet-A-Watt." March 9, 2009.
  • "Tweet-a-watt." Make: Online. January 2009.