Islands of disconnected technology can often be found in today’s high-performance homes. That rings true with one of the core renewable energy systems that typically enable zero-energy homes—that of a rooftop solar photovoltaic (PV) installation—which can often be relegated to the smart-home equivalent of a no-man’s land, as these systems are typically standalone and rarely well integrated into evolving automation platforms. Non-profit organization Pecan Street aims to bring these rogue systems into the mainstream by publishing the Sol app for iOS and Android devices, software that enables what they refer to as a check engine light service for PV system owners nationwide. The free service works in homes where an eGauge or eGauge-compatible energy monitor system has already been installed.
Certainly, there are a number of excellent standalone solar system monitoring tools available that can provide a good view of overall system production and health. But most of these systems provide energy production data only, with no visibility to holistic in-home energy consumption—a key metric toward facilitating management to a zero-energy or near-zero-energy goal. So, in order to monitor energy consumption as well as production, additional hardware and software is required, and that’s where products such as the eGauge system come into view.
Designed to deliver very granular energy consumption as well as production monitoring, the eGauge EG3000 or EG3010 from eGauge Systems can monitor up to 12 circuits in the home. Typical installations consist of a single main unit box and up to 12 current transformers (CTs)—hard-wired measuring devices that need to be clipped around circuit wiring inside the main electrical service panel—plus a networking connection to enable communication with the main unit’s built-in data logger and web server. The main unit is equipped with solid-state memory and can store an impressive 30 years of data.
The eGauge setup is literally industrial strength, as many of these systems are used in large-scale electrical utility or multi-family housing applications. The web-based interface refreshes every second and works well enough, but its engineer-centric graphical interface is designed more for commercial applications rather than the typical homeowner. There is no native eGauge smartphone or tablet app available yet, though the Web interface works fine on mobile browsers.
Sensing an opportunity to tap into the treasure trove of energy data stored in eGauge, University of Texas at Austin-based Pecan Street developed the Sol app with homeowner needs in mind. We have heard of horror stories where PV systems have gone offline for extended periods of time, and in some cases the alert mechanism is the arrival of a much-higher-than-expected monthly electric bill in the homeowner’s mailbox. Sol intends to preempt that scenario by evaluating what is happening with your PV system based on a number of data points and other factors, and then providing a daily maintenance report. Seeing the Normal indicator at the top of Sol app as it launches is a good thing.
We have been using the eGauge 3010 setup in our smart-home labs for the past two years, so were eager to put Sol through its paces. While one can get Sol up and running by simply providing the respective eGauge security credentials to the system, to glean the full value of the service the About my solar system and About my home profile tabs should be filled out. For example, the solar system profile tab requests the size of the PV system in watts, the direction and tilt of the panels in degrees, information on solar panel brand and model, and more. In similar fashion, the home profile tab enables keying of information on the size and age of the home, checkboxes for major appliances, number of residents, and other parameters. To quote the descriptive text in the Sol app: “By completing your solar system and home profiles, you improve Sol’s ability to detect possible problems with your rooftop solar panels, your home or appliances to provide recommendations that make sense to you.”
After authenticating the first time with the eGauge system, Sol downloads a year of historical data and then displays the information in easy-to-understand digital and graphical displays. In most cases, all you will need to know about your overall PV system health will be displayed on the Sol home screen, referred to as the My solar panels tab. Upon each successive launch, Sol displays a snapshot of the previous day’s solar production and consumption metrics, including:
- Solar generation – percent of home electricity use: Displays the ratio in percent of the previous day’s actual home energy usage to actual solar generation, plus comparative metrics in Month-to-date, Last month, and Year-to-date calculations.
- Value of solar generation: Displays the value in dollars of the previous day’s solar production, based on the respective electrical utility’s cost per kilowatt hour (kWh) entered on the Settings tab, plus comparative Month-to-date, Last month, and Year-to-date calculations.
- Graphical displays of current month versus previous month energy production in either kWh or dollar value
- Graphical display of monthly energy production in kWh, by month, over the past year.
Now, trying to glean the same information from the native eGauge interface would be possible, but one would have to navigate through multiple panels and drop-down menus, then resort to a calculator to generate the needed metrics. Sol does all of that and much more in mere seconds as it launches.
Want more detailed information? Clicking on the right arrows displayed in the Solar generation and Value of solar generation sections gives way to deep drill-down, at-a-glance details for 1-day, 7-day, and 30-day views in kWh, dollar value, or percentage of use measurements. That’s an impressive amount of data summarized in easily-consumed nuggets.
The real payback here for homeowners, however, goes beyond the intrinsic value of the digitized information presented in a useful and meaningful app interface. It’s manifested in the value derived from the daily Maintenance report, computed through the complex algorithms Pecan Street has employed to evaluate the daily health of the rooftop solar installation, based not only on the data bits forthcoming from the eGauge system but also from analysis of the solar system and home profiles provided by the owner, the prevailing weather conditions in the area, and comparison with other similar PV systems on the same day. That can only hasten the return for the homeowner on the investment made in a solar PV system.
There is room for improvement in the Sol app, and at the top of our wish list would be the addition of access to real-time energy production and consumption data, which is readily available through the native eGauge Web interface. With the addition of that information, there would be little reason to gaze at the complex labyrinth of the native interface. We would also like to see the ability to expand the current history drill-down details to a full year from the current 30 days. And as a final suggestion, having the Sol app integrated into the If This Then That (ITFFF) home automation environment would be the pièce de résistance for smart-home devotees.
But for tech-savvy solar PV owners with an eGauge monitoring system already installed, this free app and service can propel what was once a rogue island of rooftop technology a quantum leap forward in smarts and ready access.
