Life with a Sense home energy monitor, the first month

Measuring individual appliance's energy consumption is one thing. But Sense aims to give you a bigger picture.

TreeHugger has long hosted a debate around the correct mix of "smart" and "dumb" solutions to more efficient homes—and usually we end up agreeing that it's not an either/or proposition. Yes, it makes sense to insulate homes so well that your smart thermostat has very little to do. But it probably also makes sense to use occupancy monitoring to turn your fan off or on to keep things comfortable.

The Sense Home Energy Monitor may be a classic case in point. While it's often talked about right alongside other "smart" gadgetry like wifi-connected vehicle chargers or programmable blinds, it actually plugs into your home's data at a much more fundamental level—the service mains—in order to provide useful feedback on everything in your home, smart and dumb appliances alike.

By offering a second-by-second (actually, the sampling rate is closer to a million times a second) analysis of what your home is consuming, it provides a far superior experience to the old plug-and-play Kill A Watt-type energy monitors that you cart from one outlet to the next to measure individual appliances' consumption. But Sense doesn't just offer a picture of your whole house energy consumption, it also uses this sampling to detect the unique waveform or "signature" of different devices or appliances, and then provides data over time as to how they are being used and how much energy they are consuming.

At least, that's the idea. About a month ago, I had a monitor installed in my house, and here's how it's been working in practice so far.

Professional installation
Installation is pretty simple. The small orange box fits into your breaker panel, and a pair of white clips clamp around the service main supply and measures the current at the point that it enters into your home. The box draws its power from the breaker box, so as long as you have a spare 240v breaker you're pretty much good to go. There's no need for separate sensors on different appliances or circuits, and the box itself communicates with your phone via wifi.

Sense does recommend you hire an electrician for install because—errr—electricity is dangerous. My particular breaker box did not make it easy to access the service mains, but after a little jiggering things around my electrician was able to install it with little hassle. The only challenge I found was that my wifi signal didn't reach the breaker box, but a $20 wifi range extender soon sorted that issue out too.

Below is a video from Sense about what the installation process entails:

Easy set up
Set up was also ridiculously easy. I simply downloaded the app, set up an account, and positioned myself near enough to the breaker panel that my phone could detect the Sense monitor and do what it had to do to get up and running. You can add optional additional information to your account settings—the cost of electricity per kilowatt-hour, for example—which will help you see a more complete picture. Once the install and set up were complete, I was immediately able to start tracking energy usage.

Initial impressions
Before we started the long-term review, I met with Mike Pillips, co-founder and CEO of Sense, who cautioned me not to expect too much device-specific data when Sense fires up. And he was right. It can take several weeks for Sense to collect enough data to identify many of the common household appliances. Nevertheless, I was struck by the immediate utility of using Sense's Power Meter display to simply keep track of consumption and identify how much specific devices were using. A quick flick of the Christmas tree lights on and off, for example, revealed that I'm a really bad TreeHugger who absolutely should finish up our transition to all LED lighting soon (a similar length strand of outdoor LED lights barely registered on the monitor):

sense christmas lights display imageSense/Screen capture

And maybe a day or two after set up, Sense was already differentiating between the "Always On" load in our household, and Other—meaning devices that come off and on sporadically. This distinction alone may well help households to shave off key contributors to the "vampire power" phenomenon which costs us all so much money.

After a few days of somewhat obsessively (and annoyingly!) turning things off and on to check how much electricity they were drawing, I mostly settled back to letting Sense do its thing and start detecting devices. And here's where it gets a little confusing. So far, we have a water heater and a clothes dryer detected, and the app says it thinks it's close to ID'ing our oven and our dishwasher.

Then there are several other devices which are somewhat mysterious. Helpfully, Sense does give you clues as to what an appliance might be—whether it uses a heating element, for example, or when it was last on. By paying attention to these clues, and keeping an eye on the monitor as you switch a suspect device on or off, it should be possible over time to identify mystery devices, rename them and improve the overall user experience. (This data is also used anonymously to improve Sense's detection capabilities for everyone using the app.)

So far, this process has been a little hit and miss from my end -- due, in no small part, to the fact my house is pretty weird. The heating, for example, was once split into three different zones, and currently operates as two zones. And this appears to be throwing Sense somewhat for a loop—we have a possible heating device and a "furnace" which we suspect are actually the one furnace operating in different modes. I'm keeping an eye on these over time, and actually quite enjoying the challenge of detective work to figure these things out. (Alongside renaming misdiagnosed devices, Sense also allows you to merge devices, delete them, or report issues to Sense.) As more and more devices get identified, I can see how Sense's neat little bubble-based display for current usage will become an interesting way to understand the relative influence of different devices on our overall power demand:

sense now display screenshotSense/Screen capture

I will say I was a little surprised that I couldn't 'teach' Sense to pay attention when I turn a device off or on, or mark a specific jump or cut in consumption as being attributable to a particular device. But discussions with the data team suggest this is much more difficult than it sounds, given the relative amount of 'noise' at any given moment, and attempts at providing such features have proven to be more frustrating for users than they were worth.

Even with these early-stage challenges of device identification, I can already see the utility in watching devices turn off and on once they are identified, and also tracking usage trends over time. Indeed Mike Phillips was enthusiastic about the fact that many users don't just use Sense to track energy, but rather to tell them other things they want to know about their house. I, for example, was able to figure out that my Christmas tree light timer was on the blink, and not turning itself off. Others are using it for things like checking if the kids got home from school, or whether they left the oven on.

It's fair to say, of course, that Sense still has room to improve. But that's because what Sense is trying to do is really, really hard. My fridge, for example, reportedly confused the heck out of the data team because its signature was unlike any other fridge they had monitored. Similarly, the team guessed I was driving a Nissan Leaf (the app itself has yet to pick this up), but were confused by the charging behavior of our plug-in hybrid Pacifica. But as more people use Sense, and engage with it by providing feedback and renaming devices to more accurately reflect what they are, we can only expect the accuracy to get better.

I'm going to be reporting back on progress of the app over time, but I'm already kind of hooked. It's important to note, however, that this isn't just for the energy geeks among us. The ultimate goal—according to the folks at Sense—is not just to provide plug-in monitors for retail purchase, but rather to build smarter monitoring capabilities into every single home as standard. Once that becomes available, there's likely a whole host of other ways that technology like Sense can be used to improve efficiency, and potentially to coordinate with utilities to ensure that supply matches demand.

Please do use the comments section below to let me know any questions you may have about the Sense energy monitor. I'll do my best to either answer them through my own experiences, or refer them to the folks at Sense for more in-depth, technical responses.

Disclosure: Sense provided their home energy monitor unit at no cost for this extended review. I covered installation costs myself.

Tags: Electricity | Energy | Energy Efficiency


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