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Distribution Battery Project

A series of blue and white batteries set up in a rack inside of a metal box.

Pasadena Water and Power is launching a pilot project using Distributed Energy Resource (DER) technologies to support voltage quality during high demand intervals. PWP will be installing battery-inverter systems throughout the power distribution system which will allow PWP to shift electrical load to non-peak hours by charging and discharging. The project is estimated to benefit the city's electrical system for 8 to 10 years before service or the battery units require maintenance.

Each of the thirteen units installed has an energy storage capacity of 27.3kWh and a maximum discharge power of 5kW. The gross capacity of all 13 units combined is 354.9kWh and the gross power output discharging back onto the distribution system is 65kW. At each individual site these modest numbers are able to make an impact in curtailing load on the distribution transformer and secondary conductors by reducing overall load seen by these components during the battery discharge cycle to the tune of roughly 10% of the rated capacity of the transformer. The power drawn to recharge the units at night would conveniently happen when load in this residential neighborhood is near its lowest. The gross power able to be peak shifted is enough to keep other upstream parts of the distribution system within safe ratings for longer periods of time. This will allow for existing infrastructure to have a slightly extended life and slightly higher overall reliability. At a macro scale, spanning across the distribution circuit as a whole, power quality, specifically service voltage, should see a marginal improvement across the board. At a micro scale, voltage at individual service connections near the units will have greater improvements, while still staying in industry required voltage ranges.

Unit locations were selected to maximize voltage improvements for currently struggling services, while still providing balanced improvement for the circuit. Reduction in system losses at peak time, as well as ease of construction, were also factors taken into consideration. Advanced system modeling in a collaboration with doctoral candidates at Caltech developed the initial site selections for these installations.

Timeline and Location

Preparation for construction is tentatively scheduled to begin on March 20, 2023. The project is scheduled to be completed by April 21, 2023.

Deployment and installation will begin in late March at multiple locations between South Allen Avenue and Sierra Madre Boulevard, and Colorado and Del Mar Boulevards.

A map showing twelve areas broadly marked in between Allen Avenue and Sierra Madre Blvd (West to East) and Colorado Boulevard and San Pasqual Street (North to South)
All marked locations are approximate


Only brief interruptions at select locations will occur while connecting battery units to the grid. Lane closures and temporary street closures, lasting no more than one working day per site, will occur during the battery unit installation process. Note that access to driveways will remain open.

A lineman climbing up a telephone pole with a large battery box installed on it

A large crane parked in the street


Contact Information

For questions, please contact William Varsh, Principal Electrical Engineer, at