How does the IESO interconnection process work for commercial EV charging in Ontario?

Commercial EV charging installations in Ontario do not typically require IESO interconnection review — which applies to generation systems — but large charging deployments may trigger a local distribution company (LDC) load study if the added demand exceeds local distribution network capacity, and all installations require Ontario ESA permitting and inspection.

Clear answer

Clear answer, explained.

The IESO manages Ontario's bulk electricity transmission system and interconnection for generation projects. Most commercial EV charging installations connect to the distribution system through the local distribution company (LDC) — they do not require direct IESO review unless the load addition is exceptionally large or connects directly to the transmission system.

For large EV charging deployments — such as a fleet depot adding 50 or more Level 2 chargers, or a site adding multiple DC fast chargers — the LDC may require a load study to confirm that the local distribution network can support the additional demand without adversely affecting neighbouring customers. The LDC may require protection system upgrades or distribution network reinforcement as a condition of approval for significant load additions.

For most single-site commercial installations, the process involves obtaining ESA permits, confirming service capacity with the LDC, completing electrical work by a licensed contractor, and passing ESA inspection before chargers are energized. For projects combining EV charging with rooftop solar and battery storage, the interconnection process for the generation system runs in parallel and should be coordinated from the outset to avoid sequential delays.

Key points

What this means in practice.

EV charging is a load, not generation — no IESO review for most projects
Large deployments may trigger LDC load study requirements
LDC service capacity confirmation is required for all installations
Ontario ESA permit and inspection required for all commercial installations
DC fast chargers more likely to require LDC load and protection studies
Solar interconnection runs in parallel and should be coordinated together

When this applies

Best-fit environments.

Fleet depots installing 20 or more chargers
Commercial sites adding DC fast charging infrastructure
Projects combining EV charging with solar interconnection in Ontario
Any facility where the added EV load is a significant proportion of existing service