Important Information

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Station Capacity Calculator

For micro-embedded, small, mid-size, and large generators.
photo of a Hydro One transmission station  

We have created this capacity evaluation tool to help micro-embedded, small, mid-size and large generation applicants determine whether there is sufficient capacity to connect their proposed generation installation to one of our stations or feeder closest to, or in the vicinity of, their proposed project location.

Download the Calculator

Microsoft Excel or LibreOffice (version 3.3 or above) on either a Windows-based PC or MAC computer required. For technical help, please email us or call us toll-free at 1-877-447-4412.

Important Information for Applicants, Consultants and Contractors

  • ​We remind applicants NOT to incur major project related expenses until they receive an Offer to Connect from our team.
  • The Station and Feeder Capacity Calculator automatically tests a proposed connection using 4 criteria based on our Technical Interconnection Requirements for Micro-Embedded Generator Projects (MicroFIT TIR). Applicants who receive a “Pass” result through the calculator remain subject to capacity constraints due to the timing of when we receive their completed Form C application.

  • Applicants please carefully read Evaluating Available Capacity for Proposed MicroFIT Connections and the Terms of Use below prior to using the calculator.

  • Data included in the calculator is only applicable to our customers and NOT intended to evaluate connections to other Local Distribution Companies.

  • Users are required to enter our station and feeder for their proposed MicroFIT connection. If you require this information, please contact our Business Customer Centre. Project information such as station and feeder names are only provided to our customers, consultants or contractors with valid MicroFIT project numbers and who are listed as a project contact in our records.

  • The information may be stale-dated as soon as it is posted and should be used for information purposes only. The calculator does not allocate capacity or reserve capacity. This can only be done upon completion of an offer to connect from our team.

  • We provide only the base capacity information for the transformer stations it owns. The capacity table on the Independent Electricity System Operator’s (IESO’s) website reflects this information as well as any existing and contracted generation facilities and capacity reserved for other programs (such as the 2 MW reservation for the MicroFIT Program). Please consult the IESO website for evaluating capacity availability.


System Requirements: Microsoft Excel or 
LibreOffice (version 3.3 or higher) installed on either a Windows-based PC or MAC computer prior to being downloaded and used. For technical help with the evaluation tool, please contact our Distributed Generation Connections Group at or call toll-free at 1-877-447-4412.


Explanations of Test Criteria & Results for Proposed microFIT Connections

If there is available capacity for your proposed MicroFIT connection at the station and feeder the calculator will output “Pass”. If you wish to continue with an application for a MicroFIT connection, please apply using the Micro-Generation Connection Application (FORM C). We remind applicants NOT to incur major project related expenses until they receive an Offer to Connect from our team.

If there is no available capacity for your proposed connection the calculator will output “Fail”. The following are the test results and explanations if there is no capacity for your connection.

Test 1 checks feeder loading and feeder generation capacity limitations on the distribution system. If there is no available feeder loading capacity, the calculator will output “fail” due to no available capacity on the Feeder(s) connected to our upstream Distribution or Transformer Station as per the MicroFIT TIR.  The total acceptable generation limit and acceptable capacity for connection to the feeder has already been reached. The total current shall not exceed either 200A (for those feeders operating below 13.8 kV) or 400A (for those feeders operating at or above 13.8 kV). This criterion was developed in response to our experience of unacceptable feeder voltage fluctuations and power quality issues when a large amount of generation has been connected at a distance from the supply station, as well as to respect equipment limitations.

Test 2 checks for available thermal capacity at the distribution or transformer station and upstream transmission station. If there is no available thermal capacity, the calculator will output “fail” due to thermal limitations already being reached at the station as per the MicroFIT TIR. Generation at the distribution station shall not exceed 60% of the maximum MVA rating of the single transformer and minimum station load. These limits are necessary to protect equipment that is currently installed in the station.

Test 3 checks for the loading versus generating balance on the distribution feeder. If there is no available generation capacity, the calculator will output “fail” due to the acceptable generation limits on the feeder already being reached (total generation must not exceed 7% of the annual line section peak load on F-class feeders or 10% for M Class feeders) as per the MicroFIT TIR. Specifically, connection would not comply with anti-islanding distribution system requirements. Important note: a proposed MicroFIT connection may fail Test 3 while a FIT project (greater than 10 KW) may pass at the same station and feeder. The Station and Feeder Capacity Calculator takes into account that FIT projects will have connection requirements which will be performed at the expense of the generator. A Connection Impact Assessment (CIA) is performed for FIT projects to identify connection requirements and associated costs.

Test 4 checks for available short circuit capacity at the distribution station and upstream transmission station. If there is no available short circuit capacity, the calculator will output “fail” due to the limits already being reached as per the  MicroFIT TIR. Short circuit limits at the Transmission Station high or low voltage bus must not be exceeded by the addition of generation facilities (a bus is a conductor in a station to which elements such as transformers or transmission circuits are connected). As a result, connection of the project would create a fault level which is beyond the mandatory Transmission System Code limit, as specified in Appendix 2 of the Transmission System Code.


Terms of Use

Hydro One Networks Inc. (“Hydro One”) is pleased to provide this capacity calculator (“Calculator”) to assist generators in providing capacity information. While we believe this Calculator will be a helpful tool, we caution you that this Calculator and the information contained in or generated by it (collectively the “Materials”) are provided to you for your information only.  In that the Calculator has been established only to provide estimated capacity information, Hydro One is not in a position to confirm its completeness, timeliness, or accuracy.  In addition, Hydro One may, from time to time, make changes to the Materials without notice. Please note that information regarding capacity availability may not be current.

In no event shall Hydro One be liable for any damages of any kind related to the use or misuse of the Materials.  Hydro One is not making any representations of any kind or nature, and disclaims all warranties, whether express or implied, in respect of the Materials, including the implied warranties of fitness for a particular purpose, merchantability, expectation of privacy and non-infringement.  Notwithstanding your use of the Materials or the information generated by this Capacity Calculator. Please note that Hydro One is not allocating Capacity for your project based on the use of this tool.