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Connection Process

Hydro One has a seven-phase process for transmission connections to our grid. See the Transmission Connection Procedures and the Hydro One Tx Load Connection Customer Package for more information.

The phases after THE Optional initial Feasibility Study (Phase 0) are:

Role of Key Players in the Connection Process

Role of Key Players in the Connection Process

Icon: business in generating 


Electricity consumer. Builds and connects facilities to the electrical grid.

Logo: Hydro One Networks 

Hydro One

Licensed transmission and distribution utility. Responsible for operating and maintaining the transmission and distribution systems, including new connections once approved. Physically connects your facility and ensures safety.

Logo: IESO  


The Independent Electricity System Operator (IESO) manages supply and demand of electricity. Directs flow of electricity across Ontario. Manages conservation and energy-saving programs.

Logo: OEB  


The Ontario Energy Board (OEB) regulates electricity utilities in Ontario, including cost responsibility and electricity rates (Transmission System Code and Distribution System Code).

Logo: ESA 


The Electrical Safety Authority (ESA) is mandated to enhance public electrical safety in Ontario. The ESA must provide authorization in order for a customer to connect to the system.

Approximate Timeline

IESO Connection Assessment and Approval (CAA)

Important Connection Considerations

Technical Requirements

Conservation and Demand Management/Distributed Generation Load Adjustment Guidelines

See the Transmission Connection Procedures and the Hydro One Tx Load Connection Customer Package for more information.
The seven phases are:

Approximate Timeline

An average connection can take anywhere from under two years to over three years to complete.

Important: Various factors, such as the complexity of the project, land issues and approval processes, can extend project timelines significantly.

IESO Connection Assessment and Approval (CAA)

Customers requesting a new or modified connection to our transmission system must apply and register with us and the Independent Electricity System Operator (IESO). The IESO Connection Assessment and Approval (CAA) is a separate process that runs parallel with our Customer Connection Process and is intended to determine the potential impact on the reliability of Ontario’s transmission system grid.

Important Connection Considerations

Regulatory approvals may be required throughout the process and could have a significant impact on project timelines. They can include, but are not limited to:

  • Ontario Energy Board (OEB) approvals, such as a Leave to Construct, which is required for transmission lines in excess of 2 km.

  • Environmental approvals to construct facilities on environmentally sensitive lands.

  • Municipal approvals and permits, including land easements and land acquisitions.

  • Existing customers who are planning to upgrade their connection on Hydro One's transmission system, or who require a new or modified connection to their existing facility, should contact their Hydro One Account Executive for initial consultation.​

Technical Requirements​

Hydro One's Protection Planning Standard for Transmission Load Connections document provides load customers with a valuable guide to the protection requirements needed to support load connection applications on Hydro One's Transmission Network. This document can be downloaded below (Adobe Acrobat Reader required).​

Some of the Key Players in the Connection Process​

  • Consumer (i.e. You)

  • Hydro One

  • Independent Electricity System Operator (IESO)

  • Ontario Energy Board (OEB)

  • Electricity Safety Authority (ESA)

Conservation and Demand Management/Distributed Generation Load Adjustment Guidelines (CDM/DG Load Adjustments)​

After completing the connection process, and throughout the duration of your Connection Cost Recovery Agreement (CCRA), Hydro One will perform load true-ups to compare your submitted load forecast to actual load values. True-ups will occur at set anniversaries depending on your Customer Connection Risk Classification outlined in your CCRA. At each true-up point, you will have an opportunity to apply for load adjustments based on Hydro One’s Conservation and Demand Management/Distributed Generation Load Adjustment Guidelines (also known as "CDM/DG Load Adjustments").

See Hydro One's CDM/DG Load Adjustments resources for more information:​

Guiding Principles - CDM/DG Load Adjustments
CDM/DG Load Adjustments - For Distributors
CDM/DG Load Adjustments - For Non-distributors

Phase 0: Feasibility Study (Optional)

Approximate Timeline: 10 Months
  • A preliminary assessment of your proposed connection is performed and, if deemed necessary, an in-depth assessment known as a Feasibility Study is completed.

  • A Feasibility Study is undertaken if there are potential issues with your connection relating to location, capacity, equipment, safety, resource availability, or for other various reasons.

  • The goal of the Feasibility Study is to identify the most preferred connection option for you, while also providing an estimate of the cost of your proposed connection based on the most accurate information available at the time the study is completed.

Steps for Completing the Feasibility Study

  • Step 1

Contact Us to Get Started​
  • Email LargeAccounts@HydroOne.com – Use “Tx Load Connection Inquiry" as the subject line and indicate your interest in the Tx Load Connection in the body of the email.

  • Once received, one of our Account Executives will contact you via email, phone or, if need be, meet you in-person, to discuss your connection. The Account Executive may also provide you with an estimate of the project cost.

  • If you choose to proceed with the Feasibility Study, executing a Feasibility Study Agreement will be required.

  • Step 2

Develop the Cost and Scope of the Feasibility Study
  • The Feasibility Study Agreement outlines the scope of work and associated costs of the study.

  • Once executed and payment has been made, the study will commence.

  • The completed date of the study is to be negotiated as part of your agreement.

  • Step 3

Complete the Feasibility Study
  • Your Account Executive will provide you with the Feasibility Study upon its completion.

  • The finalized study will include an estimate accurate to within plus or minus 50 per cent of the actual cost of your connection (as assessed during that specific period) and will cover each connection option examined as part of your study.

  • Step 4

  • Approve or Reject the Feasibility Study
  • Your Account Executive sets up a meeting with you to review the Feasibility Study. Following the meeting, you are required to choose one of the following options within 45 days of the study’s completion:

  1. Accept the Feasibility Study;

  2. Request a new study, which would require you to start back at step one or two of the process above, depending on the connection and project details; or

  3. Withdraw your application and do not proceed any further.

Note: The Feasibility Study is optional to the customer and is not a mandatory stage in the connection process.

Phase 1: Connection Application

Approximate Timeline = 1-2 Months

The customer consults with their Account Executive to determine their connection requirements and discuss available options for connection to the grid. Please contact us at LargeAccounts@HydroOne.com if you are unsure which Account Executive is assigned to your company.

  • Customer Completes Entry Application

    The customer completes the Customer Connection Entry Application and provides it to the Account Executive.

  • Customer and Account Executive Complete Preliminary Assessment
  • We will meet with the customer to discuss and review available connection facilities, general technical requirements, budgetary costs, and responsibility to perform the identified connection work. Depending on the level of detail required at this stage, Study Agreements may also be required. (See Phase 3).

Phase 2: Customer Impact Assessment (CIA)

Approximate Timeline: 3-5 Months

Completion of the System Impact Assessment (SIA) and Customer Impact Assessment (CIA). The CIA is submitted to your Account Executive and the SIA is submitted to the IESO.

  • Final draft SIA is posted by the IESO
  • The final draft SIA is posted by the IESO, triggering your Account Executive to initiate the CIA. The CIA highlights significant impacts, if any, to other affected transmission customers early in the project development process, and thus, allows an opportunity for those parties to bring forward any concerns that they may have.

  • Study Agreement Negotiated
  • A Study Agreement is negotiated to determine the Terms and Conditions of the CIA.

  • SIA Completed
  • We issue a final CIA report to the Electrical Safety Authority (ESA), IESO, Connection Applicant and other transmission-connected customers in the study area, enabling completion of the SIA.

  • We Invoice the Customer
  • The customer will be invoiced for the CIA amount, if required.

Phase 3: Connection Cost Estimate (CCE)

Approximate Timeline: 4-8 Months

Phase 3 provides for the release of the quality estimates, an evaluation of any financial contribution required, and construction responsibility for the transmission facilities required for the project. This information is initiated through a Study Agreement to obtain Connection Estimates.

  • Agree on Scope of Work

    The customer and their Account Executive agree on the scope of work for the Study Agreement.

  • We Provide Requirements AND Determine Project Costs
  • We determine project costs in accordance with the Study Agreement.

  • Cost Estimate is Delivered to the Customer
  • The Account Executive delivers the cost estimates and may begin drafting the Connection and Cost Recovery Agreement (CCRA) based on these estimates. We start to examine the scope of work for estimation purposes, including which portions will be contestable and non-contestable. Contestable work is work the customer or our team can perform. Non-Contestable work is work only we can perform.

  • Customer Decides on Connection Ownership
  • The customer has three options regarding construction and ownership for any contestable portions of the projects, which includes:

    • Customer build and own

    • Customer build and transfer of ownership to Hydro One

    • Hydro One builds and owns.

Phase 4: Connection Approval and Connection Cost Recovery Agreement (CCRA)

Approximate Timeline: 1 or More Months

The Connection Approval phase places both the customer and Hydro One in a position to proceed with design and construction of the transmission facilities needed through a finalized Connection and Cost Recovery Agreement (CCRA). The CCRA is the construction agreement necessary for project design and build, and covers customer load guarantees, cost responsibility, scope of work, project schedule, and the potential transfer of any contestable assets following construction.

  • CCRA is Negotiated and Executed
  • The Account Executive and the customer negotiate and execute the CCRA based on the agreed upon scope of work in Phase 3. This step initiates the internal process to release funds to proceed with detailed engineering, order equipment, and acquire the necessary approvals, permits, and licenses for the project.

Customer and Account Executive Acquire Regulatory Approvals

Prior to commencing construction, one or more of the following items must be completed:

  • Any Regulatory, Provincial and/or Municipal approvals;

  • Real Estate and Property Agreements or Land Acquisition Agreements in place; and

  • Environmental Assessments.

  • The TCA Negotiations are Initiated
  • The Account Executive begins negotiating the Transmission Connection Agreement (TCA) with the customer in preparation for connection.

Phase 5: Design and Build

Approximate Timeline: 1-2 Years

In the Design and Build phase, the facility is designed, the Transmission Connection Agreement (TCA) is initiated, and resources and materials are procured. This phase may take up to a year or more to complete depending on the complexity of the project. The Design and Constructor (D&C) applies to our Engineering and Construction Services (E&CS) team or a third party that is hired by the customer to design and build the facilities. During this phase, the Account Executive and customer continue to work on the TCA.

  • Contestable and Non-contestable Work is Awarded to the D&C
  • The System Development Planner awards the non-contestable portion of work to Engineering and Construction Services (E&CS). The customer awards the contestable portion of work to their Design and Constructor (D&C) which could be one of our teams (if the customer chooses).

D&C Uses Our Functional Requirements

The applicable transmission design and construction standards, operating and maintenance standards and commissioning requirements are to be provided for our work and the customers work to the D&C by our System Development Planner. These will vary depending on customer facility ownership selected in Phase 4.

  • D&C Completes Detailed Engineering and Project Design
  • The connection requirements, standards, detailed engineering, project design, metering, and milestones are completed and approved by us and for our work and the contestable portions of work.

  • D&C Procures Equipment, Material, and Construction Approvals
  • The D&C procures necessary equipment, project materials, obtains the necessary easements and property rights and receives the necessary construction approval and permits.

D&C Constructs Connection Facilities 

The D&C builds the required customer connection facilities as per:

  • The Independent Electricity System Operator’s (IESO’s) Market Entry Process, which must be initiated by the customer or the Account Executive as required;

  • The Connection and Cost Recovery Agreement (CCRA) scope of work; and

  • The final approved design, taking into consideration any modifications as directed by the OEB and other provincial and municipal organizations.

Phase 6: Commissioning

Approximate Timeline: 1-2 Months

The Commissioning phase involves inspection and testing of the connection facility to prepare for In-Service, once the customer submits the final drawings.

  • CBR Finalizes the TCA
  • The Account Executive and the customer finalize the Transmission Connection Agreement (TCA) including the Operating Schedule, transmission tariffs, high-voltage equipment data, and special connection considerations. The TCA must be executed before the customer’s facilities are allowed to be placed into service.

Hydro One Facilities Commissioned

Our facilities are commissioned and we notify the IESO of equipment ready for operation.

  • Customer Facilities Commissioned
  • Customer submits Commissioning Plan 45 days prior to the In-Service date for review and comments. Customers perform and complete commissioning activities on customer-built facilities, including the submission of the COVER to us.

  • Facility is Transferred to Hydro One if AppropriatE
  • If we are to own the customer-built contestable portions of the project, the transfer takes place on the in-service date.

Connection Facility Goes into Service

Connection to our transmission grid is completed.

  • Customer Submits Final "As Built" Prints
  • Customer submits final “As Built" Connection documents and Station Single Line Diagrams (SLDs) within 60 days of connecting to our system.

CCRA is Updated with Actual Costs

We will revise the Connection and Cost Recovery Agreement (CCRA) to reflect actual costs within 180 days of connection and will provide to the customer with the final invoice, if applicable.