Pacific Gas and Electric Company (PG&E) and Tesla have started the construction of a 182.5 MW lithium-ion battery energy storage system (BESS) at PG&E’s electric substation in Monterey County, California. The system will be designed, constructed, and maintained by PG&E and Tesla and will be owned and operated by PG&E. The system is expected to be commissioned by 2021.

The BESS was approved by the California Public Utilities Commission in November 2018 and by the Monterey County Planning commission in February 2020. It includes the installation of 256 Tesla Megapack battery units on 33 concrete slabs. Along with the Megapacks, transformers and switchgears will also be installed to connect energy stored in the batteries with a 115 kV electric transmission system. The BESS will have the capacity to store and dispatch up to 730 MWh of energy to the electrical grid. PG&E’s agreement with Tesla contains an upsize option that can increase the capacity of the system to 1.1 GWh.

According to PG&E’s forecast, the BESS will save more than USD 100 million over the 20-year life of the project. This has been calculated by comparing to the forecasted local capacity requirements and associated procurement costs that would have been necessary in absence of the BESS.