The engineer comes first, and is not optional
The City of Ottawa's guidance on solar collector systems states that the design of solar collector systems and the on-site field review of their installation must be undertaken by a professional engineer licensed in the Province of Ontario. That sentence does a lot of work, and most homeowners meet it for the first time when a quote arrives with an engineering line on it.
A building permit is separately required for a solar collector system with a face area of 5 square metres or greater, which in practice means any array worth installing. The City explains the reason plainly: to ensure the building can support the additional weight of the panels and connection systems, plus wind and applicable snow loads.
Low-rise residential buildings can be exempt from that permit, but the conditions are specific. The system must be flush mounted and installed in close proximity to the roof surface, with no ballast or non-fixed attachments, and the existing roof must have been assessed by a professional engineer licensed in Ontario and deemed to be in good structural condition. So the exemption does not remove the engineer. It is the engineer's assessment that creates the exemption.
Where a permit is required, the City wants two complete plan sets, roof layouts, cross-sections with dimensions, anchorage details, confirmation that all existing structural members and connections affected by the installation have been reviewed, and confirmation that the panels and racking meet the Ontario Building Code.
The electrical side and the ESA
The Ontario Electrical Safety Code requires almost all electrical work to be reported to the Electrical Safety Authority by filing a notification of work, and it must be filed before the work begins. The ESA is explicit that in Ontario, if you hire someone to do electrical work in your home, by law it must be a Licensed Electrical Contractor.
It is equally explicit that a building permit is not the same as an electrical notification, and that you may need both. These are two separate authorities asking two separate questions, and a project can satisfy one and fail the other.
Ontario's safety alert on photovoltaic systems is short and worth reading before anyone climbs a ladder. Both AC and DC present significant hazards and both must be addressed, and small amounts of sunlight can produce a voltage potential in a PV system that could result in electrocution or arc-flash injuries. A solar panel cannot be switched off by a breaker. It is live whenever light reaches it.
The Hydro Ottawa connection, step by step
Hydro Ottawa treats residential solar as micro-generation at 12 kW AC or less, and its published process runs in three stages.
First, a service layout application: you submit a service request form indicating net metering capability. Hydro Ottawa responds with a service layout detailing responsibilities and a quotation for its own work, with a stated response of at least 15 days and up to 60 days for complex projects. Second, payment, which is required before work commences, and a service layout that remains valid for 90 days. Third, coordination and energization, and this is the gate: all preparatory work must be finished and the Electrical Safety Authority Connection Authorization must be received before the system is energized.
If your property is at the rural edge of the city, confirm which distributor bills you before assuming this process applies, because the connection procedure is not identical between Ontario distributors.
A realistic sequence and timeline
In the order things actually have to happen: choose between the Ontario rebate and net metering, because the two are mutually exclusive and they imply different system sizes. Then engage the engineer for the structural assessment and either the permit drawings or the exemption letter. Then the building permit, if one is needed. Then the ESA notification of work, filed before the electrical work starts. Then the distributor's service layout application, the payment and the installation. Then the ESA Connection Authorization, and only then energization.
Allow three to six months for the whole sequence in Ottawa, with the roof work itself accounting for two to four days of it. The variable parts are the engineer's queue, the permit review, and the distributor's own timeline. Spring is the congested season for all three.
One scheduling note specific to this climate. There is no point energizing in December. If the calendar is slipping, aim the installation at March or April rather than pushing to finish before the snow, so the array's first full months are productive ones and any commissioning fault shows up while it can be diagnosed from real production data.