As the coronavirus pandemic forces people across the country to shelter at home, utilities and grid operators are watching typical energy use patterns change in unpredictable ways, and trying to understand how this will affect their grid operations, power purchasing practices, and long-term plans.
Austin, Texas-based Pecan Street Inc. may have some answers.Â Over the month of March, the research group has been analyzing the second-by-second energy data from more than 100 homes in Austinâs Mueller neighborhood, as part of one of the worldâs longest-runningÂ real-time home energyÂ data collection efforts.
Many of these homes have rooftop solar panels,Â electric vehicle chargersÂ and smart thermostats, making them valuableÂ sources of informationÂ on how distributed energy resources (DERs) operate in concert.Â Now, they are offering a glimpse into how DER-equipped homeowners are changing the way they generate and consume energy when theyâre stuck at home all day.
While the state of Texas hasnât instituted a stay-at-home order,Â the city of Austin and surrounding Travis County ordered residents to shelter in place on March 24. Even before then, Austin canceled its South by Southwest festival on March 6, and closed its schools on March 12, putting residents on notice of the impending pandemicâs seriousness.Â
The resulting shifts in typical energy patterns have been illuminating, according toÂ Scott Hinson, Pecan Streetâs chief technology officer.Â âWe know theyâre not indicative of every household in America,â he said in an interview this week. âBut it is illustrative of what happens when you tell people to stay home, stay cool, and stay productive.âÂ
The first clear trend revealed by the data? Unsurprisingly, people staying home all day use significantly more energy âÂ and in Texas, the biggest single driver of household energy use is air conditioning. The chart below shows how energy use this March spiked significantly compared to the average usage over the same month in the prior three years.Â
âThis year, weâve had a couple of hot spells, and you can see them clearly on the chart,â Hinson said, with the three spikes on the graph corresponding to days when temperatures jumped from the mid-60 degrees Fahrenheit to the high 80s and low 90s.
But the weather does not tell the full story: Even beyond those three spikes,Â âenergy use went up more than it should haveâ compared to typical days when people are at work or school for most of the day,Â Hinson said.
By running the data through a âper cooling-degree dayâ calculation, Pecan Street estimates that air conditioner usage was up about 40 percent in the last week of MarchÂ compared to historical averages. That could have implications for utilities trying to predict increases in AC energy demand under lockdown conditions as the country moves into warmer summer months.Â
The next big findings deal with the so-called solar âduck curve,â which tracks the effect that solar generation has on typical energy supply-demand balance as it risesÂ during daylight hours and fades away in late afternoon. In solar-rich states like California and Hawaii, the duck curve has led grid operators toÂ curtail utility-scale solarÂ power and take steps to restrict rooftop solarÂ back-feeding onto distributionÂ circuits.Â
WhileÂ Texas has much lessÂ rooftop solar than those states, Pecan Streetâs participating homes have a lot more rooftop solar than the Texas average. Thatâs allowed it to track changes in the duck curve-like patterns emerging in the weeks before and after the cityâs stay-at-home order compared to previous years, as this chart indicates.Â Â
Several key observationsÂ emerge from this data, which includes both solar and non-solar homes. The first two weeks of the month (the blue line) showedÂ relatively little changeÂ compared to historical averages (the grey line).
Things got interesting during the week before stay-at-home ordersÂ but after school closuresÂ â shown with the orange line. There was a significant âflattening of the bellyâ of the duck curve, as higher temperatures led peopleÂ at home to use much more of their self-generated solar power than usual.Â
Then,Â in the final week of March, when stay-at-home orders were in full effect, the typical duck curve reemerged, only withÂ a slightly higher evening peak (the green line). It’s unclear why this last week’s data shows a deepening of the belly of the curve, given the continuation of high temperatures.Â
But as for the steepening of the duck’s “neck,” Hinson noted that Austin typically has a lively nightlife. ButÂ under lockdown, people who might otherwise go out in the evening stayed home and increased their electricity use instead, he said. Â
Pecan Streetâs EV charging data also indicates that people were driving their electric vehicles a lot less this March compared to historical averages âÂ an expected result of the cityâs response to the COVID-19 pandemic. The few spikes in the following graph are most likely tracking when Tesla owners were charging simultaneously.Â
Pecan Street has been sharing its data with municipal utility Austin Energy, which is involved in aÂ federally funded researchÂ program to assess the grid value of solar power and battery energy storage. Itâs also making it available to other utilities and research organizations, and to the general public via updatedÂ blog posts.Â Â
Suzanne Russo, Pecan Streetâs CEO, pointed out that the data canÂ help people make more informed decisions on how they manage their energy under these unusual circumstances. âAs we get into the summertime, itâs helpful for people to understand how their choices at home are going to have a bigger impact on the grid, on their community, on emissions âÂ and maybe think about some of the things they can do individually to help.âÂ