How to Monitor Energy Costs in Real-Time (Outlets, HVAC, Tesla, …)

Introduction

How much does it really cost to run the HVAC system when you are away? How much does it cost to charge that iPad? Hoverboard? Tesla? You get a monthly energy bill, but do you really know what is draining your dollars? Thanks to the wonderful world of the “Internet of Things”, you can easily setup your own real-time energy monitors without being an engineer or an electrician. This tutorial will show you how to capture your power usage using web-connected power monitors, send the data to a web service, and turn that real-time power data into an energy consumption dashboard that you can access in your web browser.

SmartThings

This tutorial will leverage SmartThings by Samsung, an easy-to-install home monitoring/automation platform. The SmartThings hub ($80 at the time of writing this tutorial) will relay data from every sensor we install to a web service. Using SmartThings as our platform of choice makes installation super simple since it is a consumer friendly platform with great documentation and support. We just have to make sure each of our sensors are SmartThings compatible.

Setting up your SmartThings hub

A Single Smart Outlet

Let’s start with something really simple – installing a single smart outlet that we can use to monitor energy usage. The SmartThings outlet costs around $45 and can be used to remotely turn things on/off and monitor the energy usage of anything plugged into it. It will take less than two minutes to connect your smart outlet to your SmartThings hub.

Setting up your SmartThings Outlet

A Web Service for Our Data

We want to stream all of our SmartThings sensor data to a cloud service and have that service turn our data into a nice dashboard that we can access from our laptop or mobile device. Our data needs a destination. We will use Initial State as that destination. Setting up the connection between SmartThings and Initial State is super easy. Simply follow the instructions at http://blog.initialstate.com/tutorial-smartthings-meet-initial-state/.

Select your smart outlet(s) under “which devices to monitor”

Once the SmartThings -> Initial State connection has been setup, every event that occurs on your SmartThings network will be timestamped, encrypted, and sent to your private Initial State account.

A Real-Time Energy Data Stream

Once your SmartThings smart outlet is installed and your Initial State/SmartThings integration has been configured, two data streams will automatically start streaming into your Initial State account – power consumption in Watts and on/off status of the outlet. The power data stream will be drawn as a line graph in Tiles (shown above) and show you a history of power consumption for your outlet. What is more interesting is to create a tile that converts Watts to energy costs by following the instructions at http://support.initialstate.com/knowledgebase/articles/1124554-real-time-expressions-compute-energy-costs. This will tell you exactly how much money is being consumed by whatever is plugged into your outlet.

How Much Does it Cost to Charge your iPhones/iPads?

The smart outlet in my kitchen was used over the course of one month as the charging station for iPhones, iPads, and miscellaneous accessories. Regularly charging these personal electronic devices only cost $0.13 in energy consumption for the entire month as shown in the dashboard above.

How Much Does it Cost to Charge a Hoverboard?

The instruction manual says that it takes two hours to charge my daughter’s hoverboard. The dashboard above shows you what happens when you charge a dead hoverboard for two hours. The power consumption rises pretty quickly to 60W then slowly increases to 70W over the course of one hour. After one hour, the power drops to 1.2W and holds for the second hour. Very odd behavior, and not what I expected. Using my energy cost tile, I see that it took a whopping $0.01 to fully charge the hoverboard.

How Much Does it Cost to Watch TV?

The power consumption of a 50″ Samsung LCD TV is interesting. When it is not asleep and there is something showing on the TV, the average power measurement is ~165W. If something dark comes on the TV like the ending credits of a movie, power will drop to about 93W, the same amount of power used if the TV is in “sleep mode”. If the screen goes all white, the power spikes to 186W. Watching TV for four hours on a run-of-the-mill 50″ LCD TV costs $0.06. If this TV was on non-stop, non-sleep mode for an entire month, it would cost ~$11 in energy to power. If this TV was on sleep mode for an entire month, it would cost ~$6 in energy usage.

Monitoring Power in your Circuit Breaker Panel

Monitoring energy usage from your HVAC or specific circuit in your house can be accomplished using a device like an Aeon Labs Z-Wave Smart Energy Meter. This device can work with your SmartThings network by following one of the guides written by the SmartThings community (example guide). These types of devices have clamps that wrap around wires in your circuit breaker panel allowing them to detect the current flow of a specific circuit. If you are uncomfortable cracking open your breaker panel, you might want to call an electrician to help. In the end, you will have something that looks like this installed:


Photograph by Matthijs Hoekstra

Once connected to your SmartThings network, connecting the data from this device to your Initial State account requires only a checkbox in your SmartThings integration setup.

How Much Does it Cost to Charge your Electric Car?

Click to view the cost progression of charging a Tesla over the course of one week

Charging your phone and tablet may not cost much, but charging your electric car certainly adds up. Placing an energy monitor clamp on the circuit driving your car charger gives you an easily accessible, real-time view of energy costs associated with charging that gigantic car battery. In the 7-day capture above, it cost $15.70 to keep a Tesla charged for daily commuting. While that cost will be dictated by how much the car is driven, you can see that the money required to keep an electric vehicle running will be a significant portion of a home electric bill. Notice the difference in max Watts logged for the Tesla, 9,923W, versus the handheld electronic chargers, 52W.

Conclusions

There is a lot of power (no pun intended) in knowing what is driving your electric bill. Every homeowner should be able to quickly figure out why their electric bill was $100 higher than expected. Monitoring energy costs will be one of the most useful “Internet of Things” consumer applications because it directly affects something that actually matters – your money. Technologies have advanced to the point that you can retrofit an existing home with energy monitors without being an engineer or writing a single line of code. The cost of energy monitors will continue to decline and the number of new homes/apartments with built-in energy monitoring will drastically increase in the upcoming months. When you finally see exactly where each dollar is going in your electric bill, you are likely going to be very surprised.

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