A Lawrence Berkeley National Laboratory (LBNL) study evaluated the performance of behind-the-meter solar PV-plus-energy-storage-systems (PVESS) in providing critical-load or whole-building backup across a wide range of geographies, building types, and power interruption conditions.
The study, conducted with NREL, found that buildings with energy storage backup could provide power for significant durations, in both simulated and real outages. The analysis covers three residential building types (single family, mobile homes, and multi-family) and three non-residential building types (hospitals, secondary schools, and big-box retail stores). It looked at 'long-duration' adverse events, lasting more than a day, usually three days.
It used simulations and also looked at ten historical events to provide a model for how the systems would cope. It assumed that the building had a 10 kWh backup to provide a basic service if power was cut. If additional loads of heating and cooling were added, then 86% of the required power could be supplied for three days.
This depends very much on the season and region where the outage takes place. However the systems generally performed well under the simulated loads. The report also examined ten historical events, which were selected from the years 2017-2020, and include five hurricanes (Harvey, Irma, Florence, Michael, and Isaias), a Public Safety Power Shutoff (PSPS) incident in California, winter gales in Washington state and Oklahoma, and thunderstorms in Iowa and Texas.
In seven of the ten events, the majority of residences would have been able to maintain critical loads, using a PVESS with 30 kWh of storage. Obviously this analysis makes various assumptions, and both situations studied are 'hypothetical' as one is simulated and the other is historical, not an record from an actual adverse event. LBNL recognizes that this preliminary study needs further work, but it indicates that PVESS systems can increase resilience and assist in managing loads in adverse weather conditions.
You can download the full report here.