What a London roof produces in a year
London roofs are modelled at about 1,151 kWh a year for each kilowatt of panel capacity installed. That covers the full calendar, from long clear summer days to winter weeks when the panels are snow covered, so it is a number to set against a year of consumption rather than a single bill. Take the system size in a quote, multiply, and you have the annual production that quote is built on, before any site-specific deductions.
Those deductions are where estimates diverge. How much of the roof faces south, what shades it and during which hours, and the pitch the panels end up at will move the result more than the choice of panel brand. A quote produced without someone looking at the roof, from either a site visit or a proper shade study, is a starting point rather than an answer.
System size itself is capped in practice at 12 kW, the band London Hydro and Ontario treat as a simplified connection. Most homes are limited well before that by usable roof area, and by the fact that Ontario credits exports rather than buying them, so building past your own annual consumption produces credit rather than income.
London Hydro: the process, the timeline and the credits
London Hydro's net metering program credits solar customers for excess generation, and credits are carried forward for up to 12 months before they expire. For systems of 12 kW or less, the customer and the Electrical Safety Authority review plans while London Hydro reviews in parallel. Once the requirements are met, London Hydro issues a connection agreement, and after ESA inspection and approval it installs a new meter.
The timeline is the thing to plan around. London Hydro states that typical small and medium projects take 3 to 6 months from application to connection. That is not the installation crew's schedule, it is the approval and connection process around them, and it means a system you want producing next summer is one you start asking about in the winter. Ask any installer to walk you through where their projects usually sit in that range and why.
On value, Ontario credits exported electricity kilowatt hour for kilowatt hour at the retail rate against future bills, with no cash payment for net annual excess. Combined with the 12 month expiry, that makes a year of your own bills the right basis for sizing. Ontario's residential pricing is time-of-use as well, which makes using your own generation as it is produced worth more than exporting it and buying it back later.
London's housing mix and what it means for your roof
Per the 2021 census, single-detached houses are about 49% of London's dwellings, apartments in buildings of five or more storeys about 22%, row houses about 13%, low-rise apartment buildings under five storeys about 10%, and semi-detached houses about 3%. Nearly half the city therefore has a full private roof to work with, while a substantial apartment population does not.
Type decides your process as much as your production. A single-detached house typically offers a full private roof for an installer to design around. A row house often has a narrower south-facing roof plane that caps system size, and a smaller array on a row house can still be a sound project as long as the quote is honest about the ceiling. Semi-detached homes generally still allow an individual install but share a roofline with the attached neighbour, so the layout has to respect that boundary.
If you live in an apartment, in a tall building or a low-rise one, the decision is not yours alone: it needs landlord or condo board approval rather than an individual homeowner permit. That is worth establishing before you collect quotes, because the answer comes from the building, not from the installer.
Heritage districts and who has to say yes
Most London homes are freehold, so HOA-style rules are not the main constraint here. For the majority of homeowners the approval chain runs through the city and London Hydro, with no board in between.
The bigger local factor is the city's heritage conservation districts. Any exterior alteration on a designated property, including a visible rooftop solar array, needs Heritage Alteration Permit approval before work begins. That approval comes ahead of the work, not alongside it, so if there is any chance your property is designated, confirm it before you pay for a design that may need to change.
Where an array sits relative to the street-facing elevation is usually the crux of a heritage review, so it helps to work with an installer who has taken a designated property through the process before. On a project already looking at a 3 to 6 month connection timeline, a heritage step that starts late is the one most likely to push you into another season.
Rebates and financing, and how they fit the timeline
Ontario's Home Renovation Savings Program is the main provincial money: launched in January 2025, with a 2026-27 program year running from April 1, 2026 to March 31, 2027 and combined rebates of up to $10,000 for solar PV paired with battery storage. Those program-year dates matter more here than in most cities, because a London project can take 3 to 6 months to reach connection, so a job started late in a program year can finish under different rules than it began under. Ask your installer to confirm current program terms at the time you apply, not at the time you first enquired.
The condition attached to that rebate is the one to read twice. Homeowners taking the HRSP solar incentive are generally directed to a load-displacement configuration rather than full net metering, so the rebate and the export credit arrangement described above are not automatically compatible. Confirm the current rules with your installer before applying.
Federal support has thinned out. The Canada Greener Homes Loan, interest-free up to $40,000, stopped accepting new applications on October 2, 2025, and only previously approved loans are still being funded. The replacement Canada Greener Homes Affordability Program, launched in September 2025, delivers no-cost retrofits through participating provinces, which do not currently include Ontario, for low to median income households, with solar federally eligible but each province setting its own technology list. Canada has no federal investment tax credit for residential solar, and some Ontario municipalities and utilities offer local financing that changes often enough to be worth asking about directly.