The bathroom is gutted. The kitchen demo starts Monday. The drywall is on order. The homeowner has been planning this for nine months. And then the electrician shows up for the rough-in walkthrough and says nine words: "Your panel cannot handle this. We need a service upgrade."
That is a bad day. A service upgrade is a meaningful line item, and the schedule slips two to four weeks because Hydro Ottawa has to coordinate the disconnect and reconnect. The homeowner is angry because nobody told them upfront.
This article is so nobody tells you that on a Monday morning. Here is how electrical load actually works in an Ottawa renovation, and how to know if your project is heading for this surprise.
What is on your panel right now
If you live in a house built before 1985, you probably have a 100-amp service. The panel is a grey or black box in the basement with somewhere between 16 and 24 breakers. That is the size of the pipe feeding your entire house with electricity.
100 amps was plenty in 1972. A house had electric heat or a furnace, a stove, a dryer, a fridge, a few window AC units, and incandescent lighting. The total connected load on a busy summer afternoon rarely cracked 60 amps.
The same 100-amp panel today has to feed: an induction range (40 amps), an electric dryer (30 amps), a heat pump (40 to 60 amps), a tankless water heater if it is electric (80 to 120 amps on its own), a hot tub (40 to 60 amps), and an EV charger at 32 to 48 amps. That math does not work. Not even close.
The renovation that pushes you over
The classic Ottawa scenario is a homeowner adding three things at once: a renovated kitchen with new appliances, a basement build-out with a second bathroom and a bar, and an EV charger in the garage. Each one in isolation is fine. Together they are 80 amps of new continuous load on a panel that was already at 90 percent.
The Canadian Electrical Code requires a load calculation before any major addition. A licensed electrician runs the numbers, including a demand factor on each circuit. If the projected load exceeds 80 percent of the panel rating on a continuous basis, the panel must be upgraded.
The 80 percent rule
You cannot operate a 100-amp panel at 100 amps. Continuous load is capped at 80 percent of the panel rating. So a 100-amp panel realistically supports 80 amps. A 200-amp panel supports 160. If your load calc lands at 95 amps on a 100-amp panel, the upgrade is required, even if the lights have not flickered yet.
What drives the cost of a service upgrade
Pricing varies by house. What matters is understanding the scope, because the scope is what moves the number. Here are the tiers of electrical work we scope in Ottawa, from least to most involved, each priced as a written line item in your proposal.
Panel-only swap (existing service is 100 amps and stays 100 amps). The lightest scope: new panel, new breakers, no change to the service entrance, mast, or meter. ESA permit and inspection included.
100-amp to 200-amp upgrade, overhead service. A larger scope: new panel, new mast, new meter base, new service conductors, ESA permit, Hydro Ottawa coordination. The mast on your roof gets replaced. The wires from the pole to your house get upgraded.
100-amp to 200-amp upgrade, underground service. Same as overhead, plus excavation if the underground feed needs upsizing. In some Hintonburg and Old Ottawa South neighbourhoods, Hydro Ottawa has to upgrade the transformer feed too, and that adds both time and cost.
200-amp to 400-amp upgrade. The heaviest scope. Required only on very large homes with multiple EV chargers, electric heat, electric water heating, and a hot tub. Rare on a normal renovation.
The sub-panel option
Sometimes you do not need to upgrade the main service. You need to upgrade what the panel can hold. If your existing 100-amp panel is full of breakers but the actual load calculation comes in at 70 amps, you have spare capacity. You just need more circuit slots.
A sub-panel is a smaller secondary panel fed off the main with a single 60 or 100-amp breaker. It gives you 12 to 24 new circuit slots without touching the service. It is one of the more affordable electrical scopes because it avoids the mast, meter, and Hydro Ottawa coordination entirely.
This is the right answer for a basement build-out where the original panel is in the basement laundry room and the new finished area needs eight new circuits. Less invasive, faster install, no Hydro Ottawa coordination needed.
The cheapest electrical answer is the one your electrician proposes after a real load calc. Not the one a contractor sketches on the back of an estimate.
The ESA permit nobody mentions
Every electrical job in Ontario over a certain scope requires an Electrical Safety Authority permit. The permit is filed by the licensed electrical contractor, not by you, not by your general contractor, and not by your handyman cousin. ESA fees in 2026 start at $98 for a small job and rise for a full service upgrade, depending on scope.
The permit pulls an inspection at rough-in and another at final. ESA inspectors will reject work that does not meet code. They will also flag illegal previous work they see while inspecting your new work. We have had jobs in Sandy Hill where the new kitchen passed cleanly and the inspector wrote up three illegal junction boxes from a 1998 basement reno that the current homeowner had no idea existed.
Your insurance company will ask for the ESA inspection certificate. Your real estate lawyer will ask for it when you sell. If you skip it, you fail those tests later, at the worst time. The fee is small. The exposure of skipping it is huge.
Knob-and-tube and aluminum wiring
Two specific Ottawa scenarios add cost.
If your house was built before 1950 and still has knob-and-tube wiring in the walls, you cannot get most insurance companies to renew without replacing it. A full replacement in a century home in the Glebe with active K&T is a significant line item, and the cost depends heavily on access behind finished walls. This work is often triggered by a renovation because pulling drywall exposes the K&T and ESA cannot let it remain.
If your house was built between 1965 and 1976, you may have aluminum branch wiring. It is not illegal but every connection has to be properly terminated with anti-oxidant compound and CO/ALR-rated devices. Insurance carriers in Ottawa increasingly want either full replacement or certified pigtailing at every connection. Pigtailing is priced per device, so the total scales with every outlet and switch in the house.
How to know before you start
Five things to do before signing your renovation contract:
- Photograph the inside of your existing panel with the cover off. Send it to a licensed electrician for a 15-minute review.
- List every new electric appliance going in: range, dryer, heat pump, EV charger, hot tub, sauna, water heater. Send the amperage of each.
- Ask your contractor for a written load calculation by a licensed electrician, not an estimate. It is a small, fixed cost up front and the best money you will spend on the project.
- Ask whether the project triggers a service upgrade or a sub-panel, and get the price in writing as a line item, not as an allowance.
- Confirm that ESA permit and inspection fees are in the quote, not added later.
If you want a quote that includes a real load calc up front instead of a Monday-morning surprise, our team handles this on every project. Call 613-862-4555 for a free 48-hour feasibility review, or check our kitchen renovation page for how electrical fits into a fixed-price scope.
The panel is one of those things you cannot see from the street. Your renovation does not care. Plan for it now or pay for it later.