Life With a Sense Home Energy Monitor, an Update

When I first wrote about the Sense home energy monitor, I was already excited about the deeper level of minute-by-minute insight it provided into my home's energy consumption. And while the Sense monitor was still in the process of identifying individual appliances and devices, the "power meter" function alone was letting me learn a whole lot more about where I am spending my money in terms of electricity consumption.

Here are just some of the insights gleaned simply from keeping an eye on the overall energy consumption:

Check the basement for vampires: Many of us TreeeHuggers spend a lot of time turning lights off and on, but there are so many devices in our homes, it can be hard to remember what is and isn't plugged in. I, for example, found a dehumidifier in the basement that was plugged in last summer and we'd forgotten about—and was adding upwards of 300W to our overall demand.

Even my gas furnace adds to the electricity bill: This probably comes as obvious to practical people who really think about how their house works. But I confess I was kind of surprised as to how much electricity our gas furnace uses for moving hot air about. With an average consumption of 597 watts, and coming on round 386 times this month alone, it's added about $6 to my electricity bill this month. (It's not clear if this is done by calendar month, or the last 30 days.) It will be interesting to see how this changes as I'll be undertaking a major upgrade to our insulation this weekend.

I should probably walk and bike even more: As I mentioned in my previous post on the Sense, the monitor has had a hard time identifying my plug-in cars—and that's still the case. But by watching the power meter, I've gotten a good—and rather stark—reminder of just how significant the demand from an electric car can be. Here's the moment our plug-in hybrid minivan got plugged in today:

Sense/Screen capture

Of course, I know the output of my charging point. And I know how long it takes my vehicles to charge, so Sense isn't really telling me anything new here. But there's something visceral about seeing that demand in relation to everything else that's going on in the house. When your consumption leaps, for example, from 500W to over 7000W, and stays there for several hours, you really start to feel that this is not a trivial amount of energy being consumed. Luckily, my kids go to the local school, I work from home and there's a growing number of bike and transit options around. Still, having Sense in my life may help keep me honest, and reduce any influence of that pesky Jevons paradox by reminding me of what we actually consume.

Many more devices detected
The "power meter" function isn't the only trick Sense has up its sleeve. Indeed, one of its biggest selling points is the fact that it's supposed to automatically detect the waveform of different devices and appliances, and analyze your consumption patterns accordingly. Last time I wrote, the number of devices detected were few, and Sense was struggling a little with the multiple modes on my oven, not to mention the weird set up of my heating system. (We live in a house that used to be a condo.) Many of these challenges remain, but Sense has started to detect considerably more devices, and is doing so mostly accurately to the best of my knowledge. Here's some of what's currently been identified (alongside several "heat" devices, our vacuum cleaner, and our water heater):

Sense/Screen capture

I will say that as Sense discovers more devices, it does become easier to see the utility in it—I can check now, for example, if I left the basement light on. And, because we are narrowing down our options, it also becomes easier to start guessing what the unidentified devices might be. That said, it's still clear that what Sense is trying to do is extremely hard and challenges remain. The numerous heat devices on my account, for example, have been hard for me to identify—and I continue to suspect that they are different modes of the same device. (Oven, possibly.) Sense's phone-only interface could also be improved to make detective work easier. Click on a specific device, for example, and it's possible to see a dedicated "power meter" display that shows consumption of just this device only. But to find that consumption you must scroll through the timeline—and it's easy to miss a device that's only on in short bursts. The ability to "jump" to the last time a device was used and/or a list of the last X times a device was on would greatly help a user in narrowing down what it actually is. (It would also help if there was a computer version of the interface—but this is something that Sense is actively working on.)

The case of the difficult dryer
The other device which we've had some challenges with is our clothes dryer. And I'll share those challenges—as well as the Sense team's perspective on them—because they are illustrative of just how hard what they are trying to achieve is. The dryer, an LG energy star certified model, doesn't quite behave like most dryers. When it's in energy saving mode, specifically, it runs a relatively long cycle without heat—or with only a small amount of heat—to pre-dry the clothes before a more robust drying cycle kicks in. As a result, Sense appears to "see" the dryer, but only when it starts to behave like a much more normal dryer.

Here's when the dryer actually turns on:

Sense/Screen capture

And here's when Sense "sees" it nearly an hour later:

Sense/Screen capture

I shared this discrepancy with Sense's data team, and they delved into the mystery with barely contained enthusiasm. Here's an abridged version of what Matt Fishburn of Sense shared with me about what they found out:

Your dryer has three different components in it, they turn on three different ways, and right now Sense is only detecting one of the ways they turn on and off. As such, Sense ends up detecting about 70% of the energy that your dryer uses.
Your dryer has a 120V motor and two nearly identical 240V heating elements. Sense detects when both heating elements turn on at the same time. Sense misses either the motor turning on by itself, or a single heating element turning on without the other heating element.

And that, rather neatly, sums up the challenge that Sense is trying to take on. Every device type, and every device, behaves a little differently. And within that device, there will often be several different modes or functions that will each have their own wave form. Here, for example, is a comparison that Matt shared with me of my dryer versus a standard dryer using their own data monitoring interface.

First, mine:

Sense/Screen capture

And then here's what a more normal dryer—or more normal person's dryer—might look like:

Sense/Screen capture

It's easy, even for a technological dullard like me, to see that these two things are not alike. So I don't by any means fault Sense for not yet perfectly capturing every device that's out there. What's also evident to me is that Sense's team is very, very interested in and passionate about what they are doing. As more early adopters start using this monitor—and renaming devices and giving feedback to the team—I suspect we'll see accuracy, utility and usability improve considerably. When I met with co-founder Mike Philips he shared that the ultimate goal would be for Sense to not just identify device type, but to be able to tell the make and model too. And then to use that information to not just monitor consumption, but to start diagnosing problems too.

That day may be a little while off, but I for one am already very grateful for the insights I'm getting into our household's overall power consumption, and I'm convinced that it will definitely help us shave a significant amount off of our overall bills.

More to come. I'll keep you posted.

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