From storms to squirrels: what causes power outages?

Equipment failure

When this happens, crews work to locate and isolate the affected equipment and make the necessary repairs. Where possible, we’ll begin switching (transferring customers to alternate circuits) to restore power to as many customers as possible while we work on the original issue.

Wildlife contact

Nature can be unpredictable, especially around electrical equipment. Sometimes, wildlife encounters power equipment and that can lead to outages.

To help reduce these types of interruptions, Toronto Hydro takes preventative steps across the system. This includes regular patrols to look for signs of animal activity and installing protective guards and enclosures where needed.

While we can’t completely animal-proof our system, these steps help keep wildlife safe and your power on.

Vehicle collisions

Some power outages happen when a vehicle hits a power pole or other electrical equipment. When a collision affects electrical equipment, safety is always the top priority.

Once the area is safe, crews assess the damage and begin repairs. If possible, they’ll reroute power to nearby homes and businesses using alternate circuits, though customers closest to the damage may be without power until repairs are finished.

Dig-ins

Outages can also happen when underground equipment is accidentally damaged during digging — something often called a “dig-in.”

Because the damage is underground, repairs can be complex and time consuming. Crews typically have two options: fix the damaged cable where it is or reroute power along a different path. In some cases, they may set up a temporary solution while permanent repairs are underway.

It’s similar to discovering a burst pipe under your driveway. You need to figure out exactly what’s going on before you can fully fix it and sometimes that means putting a short-term solution in place first.

It’s also a good reminder to always contact Ontario One Call before you dig to locate underground lines — it helps keep everyone safe and the power on.

Tree contacts

Trees can grow into or fall on lines naturally, even without storms, which can interrupt service. When this happens, crews are sent out to safely clear the branches and check for any damage before making repairs.

Extreme heat

Periods of extreme heat can put added strain on the electricity system, and in some cases, lead to power outages in parts of the city.

High winds

High winds are a common cause of outages, bringing down branches, damaging equipment or causing objects to hit powerlines. These impacts can interrupt electricity service, sometimes across multiple neighbourhoods at once.

During widespread events, restoration can take longer as crews respond to multiple locations. They work to assess damage, make areas safe and restore power as quickly as conditions allow.

Flooding

Flooding can lead to power outages when water damages electrical equipment. Because conditions can be complex, repairs may take longer as crews work carefully to restore power safely.

Freezing rain

Freezing rain can coat powerlines, trees and electrical equipment with ice. The extra weight, especially when combined with wind, can cause branches to fall or poles to come down. Ice and moisture can also impact equipment and lead to outages. During severe storms, bad road and weather conditions can make it harder for crews to reach affected areas, which may slow restoration efforts.

Loss of supply

Some power outages can happen when power isn’t reaching our system from Hydro One, often called a “loss of supply.”

Ontario’s grid has three main steps: generation, transmission and distribution. Power is generated by organizations such as Ontario Power Generation, transmitted by Hydro One, then distributed locally to homes and businesses by Toronto Hydro.

If there’s an issue on the transmission side, it can interrupt supply to our customers. In these cases, restoration depends on when power is restored to our system. Once it is, crews work to reroute electricity where possible to get as many customers back online as they can.