WDG interconnection

Unleashing an underserved market

Bringing more clean local energy to California

Interconnecting a wholesale distributed generation (WDG) project to the grid in California can take years, and it can be arduous and expensive. Fixing the WDG interconnection process will result in significantly more clean local energy in the state.

What is WDG?

A crucial market segment

WDG refers to distributed energy generation, often commercial-scale solar, that interconnects to the distribution grid and serves local loads while avoiding any use of the transmission grid. Rather than serving one customer, these systems can serve an entire community, while avoiding the expensive, inefficient transmission lines required by remote power generation. WDG provides these and many more benefits.

Why we need to fix WDG interconnection

Because of the current uncertainty and extra costs involved in interconnecting a WDG project to the grid in California — which can take years  —many projects never get off the ground. Many more are not even being considered. Fixing the WDG interconnection process will result in significantly more clean local energy in the state.

Principles for reforming WDG interconnection

  • Transparency: Too often, interconnection information is hard to access. Developers, policymakers, and others must have full, easy access to interconnection studies, queues, costs, and grid maps.
  • Accountability: Utilities must adhere to clear and consistent rules and timelines.
  • Cost certainty: Developers must know, as early as possible, how much it will cost to connect a project to the grid.
  • Distributed generation priority: Local distributed generation projects should have priority over large, centralized power projects that rely on inefficient, expensive long-distance transmission.
  • Interconnection 3.0: With innovations in grid technology and interconnection processes, utilities will be able to run simple computer simulations to determine whether a new generation project can connect to the grid.

WDG Interconnection Pilot

The WDG Interconnection Pilot has the goal of facilitating interconnection for WDG projects.

The pilot was established by the Peninsula Advanced Energy Community (PAEC) Initiative, which seeks to educate policymakers and stakeholders on beneficial reforms that will keep interconnection processes efficient and cost-effective while maintaining a safe and reliable electric grid.

The trouble with WDG interconnection

The current interconnection process presents a significant problem that must be fixed if we are to unleash WDG — the market segment that Germany targeted, propelling the country to become a global clean energy leader.

Because of the uncertainty and extra costs of interconnecting a WDG project in California, many projects never get off the ground, and many more are never even considered. 

Compared to the process for identically sized and similarly sited net energy metering (NEM) projects in California, interconnecting WDG projects costs significantly more, takes longer, and is far less predictable.

Project type Average utility charges per project Average timeframe Cost predictability
NEM projects up to 1 MW $150 105 days Standardized flat fee
WDG projects up to 1 MW $150,000 137 days Individual costs, estimated case by case, and subject to post-contract revision

A significant roadblock for developers of WDG projects is the lack of predictability. Currently, for these projects it’s not possible to use publicly available information to determine impacts and costs prior to completing an application. The costs incurred prior to being able to submit an application vary widely, but they can typically exceed $50,000, with upgrades averaging $150,000 for a 1 MW project. This presents a major risk for developers.


Streamlining WDG interconnection

We have solutions now for streamlining WDG interconnection. Funded by a grant from the California Energy Commission (CEC) and led by the Clean Coalition, the Peninsula Advanced Energy Community (PAEC) Initiative studied the barriers to interconnection and presented recommendations for improvements.

Best practices for interconnection

In its report Best Practices: Interconnection for Local, Commercial-Scale, Renewable Energy Projects, the PAEC Initiative developed recommendations for streamlining interconnection.

Recommendations include:

  • Transparent application and review processes
  • Predictable and reasonable timelines
  • Enhanced queue management
  • Dispute resolution procedures
  • Clear cost-certainty measures

Interconnection pilot

The PAEC Initiative also designed a Pilot for Testing Streamlined Interconnection Procedures, which aims to replicate the streamlined NEM interconnection process, timing, and pricing for qualified WDG projects.

The pilot includes:

  • Published grid hosting capacity information to show what size of projects can be installed without grid upgrade costs. Supplying grid information supports optimized project proposals and reduces modifications, withdrawals, and applicant friction.
  • A standardized interconnection flat fee where upgrades are not required (based on average actual costs incurred by PG&E).
  • Timely scheduling and completion of site visits for physical inspection, interconnection, and any necessary adjustments on the utility grid.

In addition to streamlining the interconnection process for WDG projects, the pilot’s goals include:

  • Reducing staff time and cost for interconnection review
  • Encouraging or incentivizing project applications that deliver benefits such as mitigating local grid needs or constraints
A Solar Siting Survey conducted in the PAEC region identified over 65 MW of commercial-scale solar potential on rooftops, parking lots, and parking structures

Rule 21

Electric Rule 21 is a tariff in California that describes the interconnection, operating, and metering requirements for generation facilities to be connected to a utility’s distribution system.

As the state with much of the earliest growth in distributed resources, California has identified state jurisdictional interconnection issues long before they have cropped up elsewhere. The state’s tariff and rules continue to serve as the foundation and model for other states’ regulations on interconnection.

The Clean Coalition has been a leading intervenor in and contributor to these efforts: developing new tariffs to accept WDG projects; publishing interconnection capacity analysis (ICA) maps, pre-application reports, unit cost guides, group study and guaranteed cost envelope options; and incorporating energy storage and advanced inverter standards.

Hosting or interconnection capacity analysis

Hosting capacity analysis (HCA), or interconnection capacity analysis (ICA), involves a proactive assessment of the existing distribution grid to understand which locations have the capacity to accommodate new DER, which makes interconnection of these resources quicker and cheaper. Grid maps, with details on available capacity down to the circuit level, are made publicly available and are regularly updated.

In California, the Clean Coalition has played a major role as a leading advocate for the state’s ICA maps, most recently updated to ICA 2.0 in December 2018.

Learn more



Regulatory filings

Media coverage

We adopt the Clean Coalition’s recommendation to require the IOUs to provide the ‘available capacity’ at the substation and circuit level, which we define as the total capacity minus the allocated and queued capacity.

California Public Utilities Commission
Decision 10-12-048, Renewables Auction Mechanism

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