Ontario Net Metering Guide: Hydro One and OEB Interconnection Rules

Key Takeaways

• Ontario net metering operates under O. Reg. 541/05 made under the Ontario Energy Board Act, 1998.
• Hydro One classifies systems 12 kW or less as micro-generation, connected via a streamlined Form C application.
• Generation credits roll over on a consecutive 12-month period to offset future electrical consumption.
• The Electrical Safety Authority (ESA) requires Plan Review for systems exceeding the 12 kW threshold, raised from the historical 10 kW limit.
• Rapid shutdown compliance is mandated for all rooftop photovoltaic arrays under CEC / OESC Rule 64-218.

The Legislative Foundation: O. Reg. 541/05 and OEB Mandates

Connecting a residential solar photovoltaic system to the Ontario electricity distribution grid is governed by provincial regulation. Specifically, sub-section 7.(1)(f) of O. Reg. 541/05 (Net Metering) made under the Ontario Energy Board Act, 1998 sets the legal framework requiring Local Distribution Companies (LDCs), including Hydro One, to offer net metering service.

Under net metering, a bi-directional smart meter registers electricity delivered to the grid and electricity consumed from the grid. When solar production exceeds household load, excess electricity flows back into the distribution network. The utility converts these surplus kilowatt-hours into monetary credits calculated at your applicable retail volumetric consumption rate. Under O. Reg. 541/05, excess generation credits can be carried forward for a consecutive 12-month period to offset future electricity costs. This annual settlement cycle allows high summer solar credits to offset winter heating and lighting bills before resetting.

Homeowners can optimize their generation value across rate structures. Customers can choose between tiered, time-of-use (TOU), or the ultra-low overnight (ULO) price plan. Depending on your home's charging requirements for electric vehicles or daytime occupancy patterns, pairing solar generation with specific time intervals optimizes your net electricity expenditure.

Hydro One Connection Pathways: Form C vs. Form B

Hydro One, Ontario's largest transmission and distribution provider, segments distributed generation interconnections into distinct capacity tiers to manage distribution grid stability and transformer thermal thresholds.

For residential systems, the threshold is clear:

• Micro-Generation (12 kW or less): Information on connecting micro generation (up to 12 kW) to Hydro One's system is available through the customer connections portal. Applicants submit Form C - Micro Generation Connection Application (for projects 12 kW or less in size). Form C bypasses complex engineering impact studies, allowing fast-tracked utility approval.
• Small Generation (Greater than 12 kW): Installations exceeding 12 kW require a Form B - Connection Impact Assessment Form (for projects greater than 12 kW in size). Form B initiates a formal Connection Impact Assessment (CIA) conducted by Hydro One distribution engineers to evaluate local feeder capacity, reverse power flow, and substation protection settings.
• Three-Phase Systems: Hydro One enforces specific Technical Interconnection Requirements (TIR) - micro generation & small generation 3-phase less than 30 kW.

If applicants require technical guidance during preliminary planning, Hydro One operates a dedicated generator connections hotline at 1-877-447-4412.

Recent legislative updates have expanded consumer flexibility. Effective July 1, 2022, amendments were made to Ontario’s net metered regulation. These statutory revisions enable third-party ownership arrangements for net metering, such as leasing, financing, and power purchase agreements. Previously, the property owner was legally required to directly own the generating assets.

Electrical Safety Authority (ESA) Standards and the 12 kW Plan Review

In Ontario, compliance with utility requirements alone is insufficient. Every electrical installation must be permitted and inspected by the Electrical Safety Authority (ESA) in accordance with the Ontario Electrical Safety Code (OESC), which adopts CSA C22.1 (Canadian Electrical Code) with Ontario-specific amendments.

Renewable energy systems are governed by Section 64 of the OESC. Under the Ontario Electrical Safety Code (OESC), installations within the scope of Section 64 - such as solar photovoltaic systems and energy storage systems (ESS) - carry rigorous safety mandates.

Historically, the ESA mandated a comprehensive engineering Plan Review submission for any renewable generation project exceeding 10 kW. The existing 10 kW threshold had been in place since 2007, when it aligned with earlier renewable energy programs and typical system sizes. However, advances in high-output module efficiency meant that standard residential equipment frequently exceeded 10 kW.

In some cases, installers selected standard equipment sizes that fell between 10 and 12 kW even when the project’s energy needs were lower, triggering costly engineering review delays. To resolve this bottleneck, the ESA issued an approved Director’s Order on Ontario Electrical Safety Code Rule 2-010. The Director’s Order increases this threshold from 10 kW to 12 kW and applies to the systems noted above. This regulatory modernization harmonizes the ESA Plan Review threshold with Hydro One's 12 kW Form C micro-generation limit.

Emergency Response and Rapid Shutdown Mandates

Rooftop photovoltaic arrays generate hazardous direct current (DC) voltages whenever sunlight strikes the modules. To protect firefighters, roof workers, and maintenance personnel, OESC Rule 64-218 requires rapid shutdown capability for photovoltaic systems, enabling emergency responders to safely de-energize the system.

Rapid shutdown limits conductor voltages inside and outside the array boundary within 30 seconds of system initiation:

1. Module-Level Power Electronics (MLPE): Systems incorporate microinverters or DC-to-DC optimizers with integrated rapid shutdown transmitters to reduce array boundary conductors to safe low-voltage limits (under 30V).
2. First Responder Access: A dedicated, labeled emergency rapid shutdown switch must be positioned near the primary service entrance, clearly identified with standardized red-and-yellow safety placards.
3. Storage Disconnects: Energy storage systems installed alongside solar arrays must feature independent AC and DC isolation switches accessible to emergency personnel.

Energy Storage Integration with Ontario Net Metering

Recent regulatory modernizations have transformed how home energy storage operates in Ontario. Net-metered customers can now pair energy storage with renewable energy systems. By integrating battery storage, homeowners can store excess solar generation during peak midday hours and discharge energy during expensive on-peak or mid-peak pricing intervals under TOU rates.

When planning your system economics, examine provincial capital incentives and payback horizons. The Canada Greener Homes Grant and Loan programs are closed to new applicants, so residential installations rely on utility billing frameworks for ongoing returns. For a broader economic comparison across jurisdictions, see our report on solar panels cost and payback by province and our audit of the Canada Greener Homes Loan and solar rebate status, which is officially closed to new applicants.

Safe Operation and Qualified Contractor Interconnection

Connecting a generating system to the provincial distribution grid involves high voltages and backfeed hazards. Installers must isolate circuits, de-energize main service panels, and utilize insulated tools during connection procedures to prevent accidental shock, arc flash, or equipment damage. Never attempt unauthorized interconnections without Hydro One authorization and an ESA Certificate of Inspection.