In short
- ESA's worked example: a 1,500 sq ft house with central air, an electric range, a dryer, an electric water heater and a 32 A Level 2 charger calculates to 108.6 A, so the minimum service is 125 A.
- The code also allows a measured method: the highest hourly reading from the last 12 months of utility data, plus 25%, plus the full rating of the new load.
- When an energy management system watches the service and controls the EV charger, the charger can be left out of the calculation.
Typical prices in Ottawa
| Job | Typical range | Notes |
|---|---|---|
| Basic panel replacement | $1,500–$3,000 | Canada-wide guide |
| Full service upgrade: meter, wiring and panel | $3,000–$5,000 | Canada-wide guide |
| Meter base or mast upgrade | $500–$1,500 | Canada-wide; when the current setup cannot carry more capacity |
| New 100 A panel, same size | $2,500–$3,500 | One Ottawa firm’s published list |
| 100 A to 200 A upgrade | $3,000–$5,000 | Same firm’s 2026 cost guide |
| 100 A to 200 A upgrade | $1,800–$4,000 | Same firm, its 100 A vs 200 A page |
| ESA permit and inspection | $150–$250 | Same firm’s list |
Sources. HomeStars, Costs to Upgrade Electrical Panel, Canada-wide, updated 21.08.2026, seen 29.10.2026. One Ottawa firm’s published lists: 2026 panel upgrade cost guide and 100 A vs 200 A page, seen 29.10.2026. Code: ESA Bulletin 8-3-15, Maximum circuit loading and demand factors (October 2023) and ESA Bulletin 86-1-7, Electric vehicle charging systems (May 2025), seen 29.10.2026. Inspection: ESA, Notifications and Inspections, seen 29.10.2026. Utility: Hydro Ottawa, Electrical service requests and Track your usage, seen 29.10.2026. Contracts: Ontario, guide for home renovation businesses, seen 29.10.2026.
What the number on the main breaker means
The service size is the current your house can draw from the street at once. At 240 volts, 100 A works out to 24,000 watts on paper and 200 A to 48,000. The panel is the box that splits that supply into circuits. A panel can be replaced at the same size, and a service can be raised to 125 A or 200 A, which means a heavier cable and can also involve the meter base and the mast.
Ontario’s electrical code asks one question: do the planned loads fit the service? It gives the electrician two ways to answer it.
Method one: the calculated load
Rule 8-200 adds up the house on paper. ESA’s Bulletin 8-3-15 walks through a 1,500 sq ft house:
| Load | Counted as |
|---|---|
| Basic load, first 90 m² | 5,000 W |
| Additional area, here 50 m² beyond the first 90 | 1,000 W |
| Central air, 4 kW | 4,000 W, full rating |
| Electric range | 6,000 W |
| Level 2 charger, 32 A at 240 V | 7,680 W, full rating |
| Dryer and electric water heater | 25% of their ratings |
The total comes to 26,055 W, or 108.6 A, and the minimum service lands at 125 A. The charger is the line that moves this house past 100 A. Electric space heating goes in as its own line, and when heat and air conditioning are interlocked only the larger one counts.
Method two: what your meter recorded
Rule 8-106 lets the electrician start from real use. ESA’s bulletin takes the highest hourly kWh reading the utility recorded over the last 12 months, adds 25% to allow for diversity during the hour, and converts it to amps at 240 V. In ESA’s example a 9.99 kWh peak hour becomes 52 A, which leaves about 38 A to 48 A for new loads on a 100 A service, depending on the size of the service cable.
Hydro Ottawa customers can download up to 24 months of hourly usage from MyAccount, in Excel, PDF or Green Button format. Attach that file to your request.
The loads that decide it
- Level 2 EV charger. Counted at its full rating without energy management. See the EV charger page for the rest of that job.
- Heat pump. Counted at 100% of nameplate. Electric backup heat without an interlock is added on top.
- Electric baseboards or a furnace switched to electric. Space heating is its own line in the calculation; see electric heating.
- Hot tub. ESA’s measured test: 12-month peak plus the hot tub’s full rating, at or under the lesser of the conductor and breaker ratings.
Staying on 100 A: the two tools
An energy management system (EMS) watches the service with sensors and turns the charger down or off when the house is busy. Under Bulletin 86-1-7, when the EMS monitors the service conductors, the charger’s load is left out of the calculation. When it watches only the branch circuit, the charger counts at the limit the EMS allows.
Some chargers can also be set below their nameplate current. ESA permits that on fixed equipment when a permanent label states the setting and the adjustment is locked behind a tool or a password.
Going to 200 A in Ottawa
A service change goes through Hydro Ottawa. The Service Request is due three to four weeks before the work, and Hydro Ottawa’s customer layout can include a visit to the site, a cost estimate and an assessment of the service loading. The new service is inspected before power is restored. The panel upgrade page covers those steps and who owns the mast.
The price gap between the two
HomeStars’ Canada-wide guide puts a basic panel replacement at $1,500–$3,000 and a full service upgrade with meter, wiring and panel at $3,000–$5,000. One Ottawa firm lists a new 100 A panel at $2,500–$3,500 and the move to 200 A at $3,000–$5,000 in its 2026 guide, while its own 100 A vs 200 A page says $1,800–$4,000. A meter base or mast adds $500–$1,500 when the current one cannot carry the new size. The panel upgrade cost guide breaks those lines down.
Ontario requires a written agreement for any contract worth more than $50. When an estimate is part of the contract, the contractor cannot charge more than 10% above it unless you have signed a change.
What to put in your request
- The main breaker size, or a photo of the panel with its door open.
- What you plan to add, with sizes if known: charger amps, heat pump model, hot tub.
- How the house is heated now and what heats the water.
- Your Hydro Ottawa hourly usage file, if you can download it.
- A question for the company: which method did you use, and what load did you get?
Who you are dealing with
Ottawa Electric Desk passes your request to one independent Ottawa electrical contracting company. That company calls you, sizes the service, quotes the job in writing and does the work.
Questions people ask
Is 100 A enough for my house?
It depends on what runs on it. In ESA’s own example, a 1,500 sq ft house with central air, an electric range, a dryer, an electric water heater and a 32 A Level 2 charger needs at least 125 A. Without the charger, the same list works out to about 77 A. ESA also notes that for a typical 2,500 sq ft house without electric heat (85 A calculated), the actual demand has been found to run below the calculated figure.
Can I add an EV charger and keep 100 A?
Often, yes, with one of two tools. ESA’s bulletin allows an energy management system that monitors the service and slows or pauses the charger, and then the charger drops out of the calculation. The other route is the measured method, using your last 12 months of Hydro Ottawa data. The electrician decides which applies.
Does a heat pump push me to 200 A?
It can. ESA counts a heat pump at 100% of its nameplate rating. If it has electric backup heat that can run at the same time, that heat is added on top.
What about a hot tub?
ESA answers this case directly. A hot tub can go on an existing 100 A service when the peak demand from the utility’s 12-month data plus the hot tub’s full nameplate rating stays at or under the service rating, taken as the lesser of the conductor and breaker ratings.
Does a bigger panel give me more power?
A new panel gives you more breaker spaces. The amount of power is set by the service: the cable, the meter base and the main breaker. Raising that is a service upgrade, which goes through Hydro Ottawa.
