This is the second in a series of guest posts by Ted Borer, PE, the energy plant manager for Princeton University. He is actively involved in campus and community energy efficiency and carbon emissions reduction efforts. He has over 25 years of experience in the energy industry, is a registered professional engineer, and holds both undergraduate and graduate degrees in Mechanical Engineering as well as the CEM, CEP, and LEEDAP Certifications. He has published numerous magazine articles, technical papers, and a book chapter on topics relating to energy and cogeneration.
My initial experience with the Wattvision system has been really enjoyable. This device has a very simple web order form. I opted to have it “pre-programmed” by entering a few pieces of information from the nameplate of our wireless router into the order form. It arrived a couple days after the order was placed with no expedited shipping costs or extra fees.
I could have had my ten year old hook it up – if he was tall enough to reach the electric meter. Here are the steps it took:
- Strap the sensor onto our electric meter with one flat-blade screwdriver.
- Adjust the location of the sensor on the meter with a thumb screw and verify the LEDs are flashing in synch with the dial rotation (no tools)
- Plug the sensor wire into the transmitter
- Plug in the power supply to a wall outlet
- Plug the power supply into the transmitter
- Watch as the LEDs light up and indicate power, connection to the router, and connection to the Wattvision servers.
- It worked. There was no fussing, programming, or troubleshooting at all!
- Note: The wireless router needs to be on at all times, but the computer and other peripherals can be shut down completely.
- Found www.wattvision.com on my Android phone and can now see our house power use from anywhere!
The whole “installation” took less than fifteen minutes between arrival and full functionality – including playing with the sensor on the desk just for fun to see it work (sensing dark and light) before installation on the meter. Note: The Wattvision system did not come with an instruction manual or installation CD. Amazingly, it doesn’t need one! It is truly a “plug & play” device.
Let’s step back for a moment. What do I want to do with this thing? What am I expecting of it?
Ideally, I’m hoping to learn and answer questions:
- How much electric power are we using at our house?
- Which things do we operate that demand all that power?
- What costs a lot to operate?
- What devices or behaviors could we modify to reduce our power use?
- What changes would be cost-effective without causing us great inconvenience? I’m sure there are things that we could do that we wouldn’t want to or that would be too expensive for us. We have no interest in sitting at home in a cold, dark, silent house. We just want to learn where we are wasting energy and find ways to reduce that.
- When we make changes, I want to verify that the changes had the anticipated result in power and money savings.
- I expect to have some fun playing with this new gadget.
My first insight was pretty basic: WOW! Are we really using 4000 watts this evening?!! Steadily? That can’t be right. I thought we turned off most of the stuff in rooms where no one is. Where’s it all going? For context, it’s January, the coldest month of the year. We have an electric heat pump providing about half the heat for our house and an extremely efficient fireplace providing the rest. But we also have a fairly tight house and think we’re pretty good about energy use.
After letting the Wattvision run a while and switching on and off some lights to see that it responded accurately, I looked at the “current consumption rate” graph for the previous hour. This is a green line graph with time in a blue field on the x-axis. I noted brief upward spikes about every half hour. What’s that? Perhaps it’s the well pump coming on to maintain water pressure in the system?
One thing that appears critical to get the most out of this tool is to observe the data and then super-impose whatever I know about what is happening at the time.
Check the “history” graph below. There is a blue line showing consumption rate in watts every fifteen seconds. It’s easy to right-click on the blue time axis and to use the mouse wheel to expand and contract the time range.
It looks like we were only using about 500 watts between midnight and 2:30 am. Then power use jumped up. Here’s my guess at what happened: The bread machine was set on a timer to have bread ready for us at 6:30 AM. It takes about four hours to cook. So it should have started automatically at 2:30. The only problem is that the bread was finished at 6:30 and power use continued at a relatively steady 4kW even after that. Was it also the heat pump that increased power demand?
So what’s happening in the graph above? It looks like the electric dryer ran from mid-morning until 11:47 AM, then shut off. The dryer heating element must use about 5500 watts. I can verify that by checking the nameplate or owner’s manual. Let’s do some easy math. Say the dryer averages 5kW for an hour of operation. Then one clothes-drying cycle costs:
(5 kilowatts) x (one hour) x ($0.19/kilowatt-hour) = $0.95 to dry a load of clothes.
That might be off a little, but it seems about right.
The heat pump must be off or on “low” during the end of this time period. 890 watts of stuff is running. The small spike about 12:18 AM was probably the microwave heating lunch.
This is pretty cool! More to come! Buy a wattvision sensor for your house at wattvision.com.