Study Shows Backup Power Of Solar Plus Storage

Study provides a first-of-its-kind, nationwide analysis characterizing the ability of solar-plus-storage systems to provide backup power during long-duration power interruptions

September 27, 2022 (Lawrence Berkeley National Laboratory)

“…[The backup power capabilities of behind-the-meter solar-plus-energy storage systems (or PVESS), a new study found,] depends, first and foremost, on PVESS sizing and the set of critical loads selected for backup. If heating and cooling loads are excluded from backup, a small PVESS with just 10 kWh of storage (the lower end of sizes currently observed in the market) can fully meet basic backup power needs over a 3-day outage in virtually all U.S. counties and in any month of the year…

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…[If] critical loads include heating and cooling, a PVESS of that size [assuming space heating primarily of electric resistance-based heating, rather than heat pumps] would meet 86% of critical load, on average across all counties and months, while a larger PVESS with 30 kWh of storage (the upper end of sizes currently observed in the market) would meet 96% of critical load…Backup coverage of heating and cooling loads varies considerably across regions…[and] tends to be lowest in regions where electric heating is common (the southeast and northwest), and also in regions with large cooling loads (the southwest and parts of the southeast)…

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…[Backup performance can also vary considerably with] the underlying building stock…Backup performance for homes with electric heat or high cooling loads is quite sensitive to weather variability…[but] fairly insensitive to outage duration beyond 1-day… In general, backup performance declines as outage duration increases, though the effect is relatively modest, given the ability of PV to recharge the batteries each day…” click here for more

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