Overview: The California State License Board contracted the University of California Berkeley (UCB) to evaluate which specific contractor licenses should be allowed to install battery energy storage systems (BESS), particularly when BESS are installed simultaneously with solar photovoltaic systems. UCB’s findings were compiled into an extensive report and submitted to the CSLB on June 30, 2021. 

Solar panel with battery energy storage system

The alternatives that UCB considered during the study were:

  • Preclude the C-46 Solar classification from installing BESS.
  • Permit the C-46 Solar classification to install BESS on residential units with stated restrictions
  • Make no change to the existing C-46 Solar classification.

Based on their findings, UCB recommended* that the CSLB, limit the capacity of the C-46 Solar license to its original specifications and preclude C-46 Solar license holders from installing BESS even if said license holder is installing solar photovoltaic systems. This recommendation comes with the caveat that the C-46 Solar license holder does not hold a separate license in which BESS installation is permitted.

This recommendation was made in large because “Research showed that the current pool of BESS installers have higher qualifications than might be the case if the CSLB rules permit the C-46 Solar license to include BESS.” 

UCB also stated that a decision to allow C-46 Solar licenses to continue with the installation of BESS could result in lower workforce skill standards, and believes it is more beneficial to support the expansion of the existing pool of contractors that hire certified electricians. 

Female contractor installing solar panel

On July 27, 2021, the CSLB will consider one of the following three options** in regard to contractor license requirements for BESS:

  • Option 1: Existing policies remain in place. The C-10 Electrical Contractor license may continue to install BESS in all applications, (A) and (B) license holders may install BESS within existing classifications, and C-46 Solar Contractor license holders may install BESS only when paired with the installation of a new solar photovoltaic system. 
  • Option 2: Officially determine that the C-46 Solar license is not authorized to install BESS in any application due to BESS being a separate trade that is not required to install a photovoltaic solar energy system and prevalent health and safety risks identified in the report.
  • Option 3: Choose an alternative course of action not offered in the UCB study.

Industry support/opposition: The following associations have voiced their support or opposition.

The California Solar and Storage Association (CALSSA) strongly advocates for the C-46 Solar license to include BESS.

  • The CALSSA claims, “the concerns over safety are a sham and cites what it describes as the impeccable record of California’s solar installers, most of whom hold C-46 licenses.

The International Brotherhood of Electrical Workers (NECA/IBEW) strongly advocates for the C-46 Solar license to preclude BESS.

  • The NECA/IBEW argues, “energy storage systems are an evolving technology and the interpretation of the C-46 Solar license regulation is no longer correct. C-46 Solar license contractors should not be permitted to contract for or install BESS because these systems are independent of a solar system itself and regulations prohibit C-46 Solar licenses from performing trades or crafts except when required to install a solar system [...] Furthermore, because C-46 Solar contractors are not authorized to install BESS when they are not paired with a solar system, they should not be able to install them at all. 

CSLB Decision: The Contractors State License Board voted 11-3 in favor of moving forward with Option 2. The driving force behind this decision was safety. C-46 Solar licenses will no longer be authorized to install BESS in any application.

To view data and findings obtained from the study, click on one of the links below:

Trends in BESS installation size in California

Distribution of contractor license classifications installing BESS paired with solar in California

Distribution of contractor license classifications installing the most residential BESS projects

Distribution of contractor license classifications installing BESS projects in rural counties 

Overview and analysis of BESS safety issues


  1. https://www.cslb.ca.gov/Resources/BoardPackets/BESS_report.pdf
  2. https://www.cslb.ca.gov/Resources/BoardPackets/2021/BoardMeetingPacket072721.pdf