IESO to Carry Out Routine Voltage Reduction Tests on July 23, 2026

The Independent Electricity System Operator (IESO) will conduct routine voltage reduction tests on Thursday, July 23, 2026, as part of mandatory testing of Ontario’s electricity system emergency operating measures. These tests are performed every 18 months and help ensure the ongoing reliability and stability of the provincial electricity grid.

The test schedule is as follows:

• 3% reduction between 9:00 AM and 10:00 AM
• 5% reduction between 1:00 PM and 2:00 PM

Voltage reduction tests have three key purposes:

• To determine how much power can be reduced through the two levels of reduction
• To identify equipment problems so they can be addressed
• To help keep IESO and market participant staff familiar with procedures to execute voltage reductions and identify any deficiencies in the procedures that may need to be corrected

Impact on Customers:

• The voltage reduction tests are expected to have minimal or no noticeable impact on the public as the voltages are still expected to be within established industry standards for electrical equipment used by residential, commercial and industrial consumers.

For more information about voltage reduction testing, please visit the IESO website.

Read the full news release.