I’m a data geek—for example, I have spreadsheets of all of my utility bills going back 10 years for three different homes. Using the previous owners’ bills for our Utah home, I calculate that we’ve reduced electricity consumption by about 50%—with minimal investment. I wanted to keep an equally close watch on our PV system’s performance.
If not included in the price, inverter manufacturers’ data management options can cost anywhere from $250 to $500 (if a fixed cost), or $5 to $10 per month (if an ongoing charge). There are also third-party (non-inverter) options that can set up monitoring for similar fixed or annually recurring charges. If the data is important to you and you don’t want to DIY, buying one of these options may be worth the cost. While I was researching options, my PV installer mentioned that one of his clients was using The Energy Detective (TED) and was happy with it. After some research, I decided to try it.
Depending on which model you choose, the TED 5000 series will monitor up to four electrical circuits—your home’s total consumption; subcircuits like your air-conditioning or workshop; PV generation; etc. I chose the TED 5002-G to monitor two circuits, one for PV and one for consumption.
The TED package included two current transformer clamps (CTs) with measuring transmitting units (MTUs) to measure the current and voltage in the wires, and a gateway to collect and display the data. Physical installation was not difficult—the CT clamps wrap around the positive and negative wires and connect to the small MTU boxes. The MTU boxes were then wired into the two-pole breaker serving the PV disconnect (outside) and the whole-house disconnect (inside the circuit breaker box). I plugged the receiving unit into the wall outlet closest to our Internet router and connected them with an Ethernet cable.
The MTU sends the data through the house’s electrical circuits to the receiving unit. The data is accessible either with an optional table-top display and/or on an intranet web page through your Internet router using software embedded in the receiving unit. I’ve also set up an option to view the web page outside my house intranet by forwarding the IP address through my router’s firewall.
The TED software has a variety of options for customizing the online display and data collection, and for downloading your data to a spreadsheet for analysis. You can also link your account to a number of free, third-party energy Web services, such as myEragy, People Power, or others. These third-party options sometimes have better graphical displays than TED and can analyze and e-mail reports or alerts on your electrical usage. They are also easier than setting up your own IP address forwarding.
With either option, you can access your data anywhere in the world that you have Internet access. This can be as much for show as anything, but two practical applications include checking for power outages if you’re away from the house for an extended period of time or troubleshooting system or data errors remotely.
The TED device has been fairly accurate. I’ve compared the consumption data to my utility meter measurements on my monthly bills and, so far, the average difference is about 1.5% over a year.
I’m satisfied with TED’s performance, but some people report problems with getting the data from their transmitting units to their receiving units—other electrical appliances may cause interference on the electrical wire. Moving the receiving unit to another electrical outlet can solve the problem. Unexplained data spikes or hour-long data flat lines occasionally show up in our system, though the overall impact is minimal.
As a data-collection nerd, one major problem I had was multiday missing data after trying to test one of the third-party data management options. I didn’t notice the problem until later and then reset my TED device to fix it. Thankfully, a colleague at Clean Power Research, a company I collaborate with (see Access), provided me with hourly satellite solar irradiance data from their SolarAnywhere data service for my area for July 2011. I created a scatter graph using this data and my previous PV data to create a trend-line (see graph on previous page) and then applied the trend-line formula to the irradiance data during the data gap to recreate it. For consumption, I simply averaged my daily usage for the few days before and after the gap and called that close enough.