Two layers of rules: zoning and the PIIA
The base layer is Règlement de zonage no 1872, the general zoning by-law, which governs land use and building appearance. It is the document that answers whether an installation is permitted in your zone and what dimensional constraints attach to it. Every property in the city sits under it.
The second layer is the PIIA, the plan d'implantation et d'intégration architecturale. Unlike zoning, it does not apply everywhere: it requires a qualitative design review for the zones and the project categories that the by-law designates. That is two separate triggers, and this catches people out. A project can be pulled into review because of where it is, or because of what it is, and knowing that your zone is clear does not tell you that your project category is.
Qualitative review means judgement against design criteria rather than a checklist of measurements. For a rooftop array the recurring questions are visibility from the street, the colour and finish of panels and mounting rails, and whether the installation reads as part of the roof or as equipment parked on top of it. None of that makes approval unlikely, but it does mean the design conversation happens earlier and needs more than a panel count.
So make the call to the city the first step, ask both questions plainly, and if either answer is yes, ask what the reviewers expect to see. That single enquiry is the difference between a project that runs to schedule and one that is redesigned after the fact.
Vaudreuil-Dorion roofs and who gets to decide
The city has 16,715 dwellings and 53.3 percent of them are single-detached. Those owners can pursue rooftop solar without a co-owner vote or a landlord's agreement, subject only to the by-laws, and they are the majority of the housing stock.
6.3 percent of dwellings are row houses, and they are the distinctive case here. A row house shares its roof structure with the units on either side, which complicates a single-unit project in a way a detached roof does not: the roof plane runs across property boundaries, penetrations and flashing sit near or on a party line, and any future re-roofing is a shared event. Before designing an array on a row house roof, establish where your ownership ends, whether the roof is common property under a declaration of co-ownership, and who has to agree.
A further 5 percent are semi-detached and 2.5 percent are duplexes, which pose the same question in a smaller form: one other party to agree with rather than several. 29.9 percent of dwellings are low-rise apartment units and 2.5 percent are in high-rises, and in both the roof belongs to the building rather than to a household, so a rooftop array is a building decision with a second question attached about which meter it would feed.
The order of operations follows from that. Settle who controls the roof, then look at the by-laws, then get quotes. Doing it in the reverse order is how homeowners end up with a quoted design they are not entitled to build.
What a roof produces and what the electricity is worth
Natural Resources Canada puts Vaudreuil-Dorion's photovoltaic potential at 1,198 kilowatt hours a year for each kilowatt of installed capacity at optimal tilt. That is the figure for a well-oriented, unshaded array, so treat it as a ceiling and expect a real roof to land under it depending on pitch, aspect, shading and how long snow sits on the panels in midwinter.
On the value side, Hydro-Québec is the distributor and its residential rate stands at 7.065 cents per kilowatt hour as of April 2026. It is not a time-of-use rate. There are no peak hours in Quebec and no off-peak hours, so shifting the dishwasher to the evening changes nothing on your bill, and there is no rate-based case for a battery. The worth of a solar kilowatt hour here is simply the electricity you do not buy.
That makes the arithmetic unusually clean. Take your annual consumption in kilowatt hours from your own bills, work out the capacity needed to generate about that much at roughly 1,198 kilowatt hours per kilowatt, discount for your actual roof, and you have the honest size of the system. Everything else is detail.
How your surplus is credited, and when it stops counting
Hydro-Québec credits exported electricity one for one, in kilowatt hours rather than dollars, into a surplus bank that is deducted from later consumption. That is what makes a strong summer useful in February, and because the credit is held in energy it does not lose value if the rate moves. Self-generation is capped at 1,000 kilowatts, which no house comes near.
The limit that does bind is time. Every 24 months, on 31 March of each even year, the bank is reset to zero. A positive balance sitting there at that moment is settled at Hydro-Québec's average cost of supply, which is well below the retail price you pay to buy the same kilowatt hour back, and the arrangement is written so that it cannot leave you with a negative bill at any point.
That single mechanism is why the sizing advice above is not a hedge. A kilowatt hour you generate and consume is worth the retail rate. A kilowatt hour you bank and consume before the next reset is worth the same. A kilowatt hour you bank and never consume is worth very little, and on 31 March of an even year it is worth nothing. An array sized past your consumption spends real money to produce electricity that expires.
Grants and financing
The substantial subsidy is Hydro-Québec's LogisVert solar grant: $1,000 for each kilowatt of installed capacity, capped at 40 percent of eligible project costs, which Hydro-Québec describes as typically $5,000 to $6,000 on a residential system. Its own projection is that this shortens a typical residential payback from 25 to 30 years to roughly 10 to 12, which is programme modelling of a typical case rather than a number for your address.
Two dates decide eligibility. The installation must be completed on or after 30 June 2025, and the application has to reach the LogisVert portal within 9 months of the installation date. If your project goes through a PIIA review the front of the timeline stretches, but the application clock still starts at installation, so the delay does not buy you extra time to file.
Federal support has narrowed. New applications for the Canada Greener Homes Loan, interest free up to $40,000, ended on 2 October 2025, leaving only already approved loans in payment. The Canada Greener Homes Affordability Program has taken over since September 2025, offering no-cost retrofits to low and median income households via provincial partners, with solar federally eligible and each province maintaining its own technology list. Canada offers nothing resembling a residential solar tax credit.