D08 - How to Size Your Inverter for a Grid-tied Energy Storage System (ESS) – Power Resiliency in Uncertain Times

The increased stresses on our electricity grid caused by aging infrastructure, grid saturation, and severe weather events have created an unprecedented need for grid-tie residential systems to work independent of the utility grid and provide backup power for days, weeks, and even months in some cases. Whether it is hurricanes in Puerto Rico and the Caribbean, cold and ice storms in Texas, wildfires in California and other regions, grid-tie solar PV + storage systems are more and more asked to perform like off-grid systems.

This poster bridges the gap in current system design to help installers meet the growing demand for grid-tied energy storage systems (ESS). The information can be immediately applied to any residential solar plus storage installation where the customers and installers are placing a premium on backup power performance.

As an installer, it’s critical to know how to size your inverter properly for backup systems. Nuisance tripping is a significant cause of a blackout during backup system operation when the system is overloaded. In addition, it can lead to customer dissatisfaction if power is not available when needed the most. In order to avoid unwanted blackouts, installers should look beyond the inverter’s continuous power at 240V at 25°C. You also need to look at the inverter’s surge capability for short durations and its ability to handle out-of-phase imbalance overload conditions on each leg of 120V. Lastly, it’s critical to understand the inverter’s continuous power capacity at 120V.