For most Ontario businesses, commercial solar needs four sign offs: a utility Connection Impact Assessment, a signed connection agreement, a municipal building permit, and an ESA electrical inspection. At Hydro One, the impact assessment is due within 60 days of a complete application for most small projects. Plan for several months end to end, and order no equipment until the utility study is back.
Key takeaways (as of October 6, 2026)
- Hydro One requires an impact assessment for systems above 12 kW. Other utilities set their own thresholds.
- The impact assessment is due within 60 days for most small Hydro One projects, or 90 if grid upgrades are needed.
- Grid capacity is not reserved until the impact assessment is complete.
- Ontario net metering has had no 500 kW size cap since 2017.
- Many municipalities require a building permit with a structural review.
- No connection date is fixed until every approval is in writing.
What approvals does commercial solar need in Ontario?
Four main sign offs. Your local utility studies whether its grid can take your system and sets the connection cost. Your municipality issues a building permit where required. ESA inspects the electrical work. Then the utility signs a connection agreement and lets you generate. Each one has its own forms and timing.
Think of it like opening a new store. The landlord, the city and the fire inspector each have to say yes, and they work in a set order. Solar is the same, with the utility acting as the landlord of the grid.
The utility steps take the longest, so they set the pace for everything else. The rest of this guide follows Hydro One's published process, because it serves most of rural Ontario. Other utilities follow similar steps under Ontario Energy Board rules, with their own forms and thresholds.
How long does commercial solar approval take in Ontario?
Usually several months. At Hydro One, the published deadlines alone add up to well over 100 days before construction starts, and that excludes your own time to prepare drawings and sign agreements. Projects that need grid upgrades take longer. The table below shows each step and its official deadline.
| Step | Who acts | Official deadline (Hydro One, as of Oct 6, 2026) |
|---|---|---|
| 1. Preliminary consultation request (Form A) | You or your installer apply; Hydro One replies | 15 days after a complete request |
| 2. Impact assessment application (Form B) | You apply; Hydro One checks it is complete | 14 days. If incomplete, you get 14 days to resubmit, then Hydro One has 7 days |
| 3. Connection Impact Assessment study | Hydro One | 60 days for small projects; 75 days if a host distributor or transmitter study is needed; 90 days if grid upgrades are needed |
| 4. Connection cost agreement | You sign and pay | Must be done within 6 months or the assessment expires and capacity is released |
| 5. Project kickoff | Hydro One | Within 45 days of signing the cost agreement |
| 6. Connection agreement | You and Hydro One | Signed at least 30 days before connection |
| 7. Commissioning and authorization to generate | Hydro One, after ESA | Three milestones: load connection, testing, commercial operation |
| 8. Final invoice or credit | Hydro One | Within 180 days of authorization to generate, if work is done on time |
"Small projects" at Hydro One means up to 500 kW on lines under 15 kV, or up to 1 MW on lines of 15 kV or more. Mid sized projects up to 10 MW have similar study deadlines. Projects above 10 MW take longer and also need studies by the IESO and Hydro One Transmission.
Want to know what your site needs? See what commercial solar costs in Ontario, or explore our commercial solar installation service.
What is a Connection Impact Assessment?
It is the utility's study of whether its grid can safely accept your system, and what it will cost to connect. Hydro One requires one for systems above 12 kW. The study comes with a cost estimate that is only accurate to plus or minus 50%, and capacity is not reserved until the study is finished.
That last point matters. Two businesses on the same line can compete for the same room on the grid. Capacity is only allocated when a study is complete, so filing a complete application early gives you the best chance. An incomplete application adds review time, and missing the 14 day resubmission window can mean starting over.
The cost estimate is rough by design. Hydro One offers a more detailed estimate, accurate to plus or minus 20 to 30%, at the applicant's expense. Budget for the difference before you sign anything with your installer. Grid room varies by area; see how grid capacity affects solar connections in Ontario.
Is there a size limit for commercial net metering in Ontario?
No fixed size cap. Ontario removed the 500 kW net metering limit in 2017. The rule now is that your system must generate electricity primarily for your own use. In practice, that means sizing to your annual consumption, not to your roof. Many older guides still quote 500 kW.
The same 2017 changes also allowed businesses to pair batteries with net metered solar. A battery can cut peak demand costs, which matters for many commercial bills. See how peak shaving lowers Ontario demand charges and our commercial battery storage service.
Net metering credits carry forward for up to 12 months. Oversizing does not pay, because unused credits expire.
Do I need a building permit for commercial solar?
Often, yes. Toronto requires a permit for rooftop solar over 5 square metres, with structural calculations showing the roof framing can carry the system. The fee for buildings other than small residential is $425.30 per structure, as of October 6, 2026. Other municipalities set their own rules and fees.
Commercial roofs need extra care. Flat roofs often carry ballast, snow and mechanical equipment. A structural engineer usually reviews the load before a permit is issued. If reinforcement is needed, it adds time and cost, so find out early.
In Toronto, rooftop and wall mounted solar installed under the Building Code is exempt from zoning bylaws. Heritage buildings need a separate heritage review.
What does ESA require for commercial solar?
A licensed electrical contractor files a notification with the Electrical Safety Authority before the electrical work starts, and ESA inspects it. Almost all electrical work in Ontario needs this notification. The utility will not authorize your system to generate until the electrical work has passed.
Commercial systems often connect to three phase service and larger switchgear, so the electrical design is more complex than a home system. Ask your installer who files the ESA notification, and keep the certificate of inspection with your project records.
How does approval timing affect the federal tax credit?
The federal Clean Technology Investment Tax Credit is claimed based on when your equipment becomes available for use. A delay in approvals can push your claim into a later tax year. The credit's rate also steps down in later years, so timing affects its value. Confirm eligibility and timing with your accountant.
The credit is for taxable Canadian corporations, not individuals or sole proprietors, and conditions apply. Read who actually qualifies for the federal solar tax credit, and see commercial solar financing options for how businesses fund projects.
What can go wrong?
Most delays come from incomplete applications, missed deadlines, and surprises on the roof or the grid. Knowing them in advance keeps your project on schedule and your budget intact. Here are the issues that most often slow commercial projects down in Ontario.
- Incomplete applications. Missing information restarts review periods.
- Letting the impact assessment expire. If the cost agreement is not signed and paid within 6 months, capacity is released.
- Connection costs above the estimate. The first estimate is only plus or minus 50%.
- Grid upgrades. They extend the study to 90 days and can add cost.
- Roof reinforcement. Structural review can require work before a permit is issued.
- Ordering equipment too early. If the utility says no or asks for changes, you may own equipment you cannot use.
- Oversizing for net metering. Credits expire after 12 months.
- Assuming dates are fixed. No connection date is guaranteed until all approvals are complete.
Frequently asked questions
How long does commercial solar take to approve in Ontario?
Usually several months. Hydro One's published deadlines alone exceed 100 days before construction, and grid upgrades add more. Your utility, municipality and roof all affect timing.
What size of commercial solar system needs an impact assessment?
At Hydro One, systems above 12 kW. Other utilities set their own thresholds, and some older documents still list 10 kW, so check with yours.
Is commercial net metering capped at 500 kW in Ontario?
No. The 500 kW cap was removed in 2017. Systems must generate primarily for your own use.
What does a Connection Impact Assessment cost?
Utilities charge a study fee that varies by utility and project size. The connection work itself is estimated in the study, accurate to plus or minus 50% at Hydro One.
Can my business add batteries to a net metered solar system?
Yes. Ontario allowed storage with net metering in 2017. The battery is part of your connection application, so include it from the start.
Do I need a building permit for solar on a commercial roof?
Often, yes. Toronto requires one above 5 square metres, with structural calculations. Fees and rules vary by city.
Who applies for the approvals?
Your installer usually prepares and files the utility, permit and ESA paperwork for you. You sign the agreements and pay the utility fees. Confirm this in your contract.
When should I order equipment?
After the impact assessment is back and you know the connection cost. Ordering earlier risks paying for equipment you cannot connect.
What happens if the impact assessment says the grid is full?
The study explains what upgrades would be needed and what they would cost. You can proceed with upgrades, resize the system, or ask whether a different design would fit the available capacity.
Does approval timing affect the federal tax credit?
It can. The credit is based on when equipment becomes available for use, and its rate changes in later years. Ask your accountant how your timeline affects your claim.
Get your approval path mapped before you commit
Every site is different: your utility, your roof, your load and your grid connection all change the path. Send us a recent electricity bill and your site address. We will outline the approvals your project needs, the order they happen in, and what could slow them down. No pressure and no obligation. Contact Solar X or see our commercial solar service.
Sources
- Hydro One: Connection process for distributed energy resources
- Ontario Energy Board: Net metering
- O. Reg. 541/05: Net Metering (Government of Ontario)
- City of Toronto: Building permit guide for solar collectors
- Electrical Safety Authority: electrical contractors and notifications
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Written by the Solar X Team. Last updated October 6, 2026. Method: deadlines are taken from Hydro One's published connection process and apply to Hydro One projects; other utilities differ. No calculated figures are used. Thresholds, fees, and tax credit terms change, confirm current details with your utility, municipality, the Electrical Safety Authority, and your accountant before making decisions.