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EV Charger on 100 Amp Service in Ontario (2026): The Load Calculation, EVEMS Load Managers, Lower-Amp Charging, Two EVs and When a 200 A Upgrade Is Really Needed
Electrical & Lighting
A Charger on a 100 Amp House: Often Yes, Sometimes No, and the Arithmetic Decides, Not the Salesman
Plenty of Ontario houses still run on 100 A, and plenty of their owners have been told the charger means a $4,000 service upgrade first. Sometimes that is true. Often a load manager or a charger turned down a notch does the job for a fraction of it. This page walks through the load calculation the code requires, in plain words, on a real-sized bungalow, and shows where each answer comes from.
The numbers
24,000 Wthe floor the calculation cannot go under: 100 A
7,680 Wa 32 A charger, counted at 100 percent
$1,000EV load manager installed, default
$3,800100 to 200 A upgrade, overhead, default
| Way to add the charger | Range | Default or note |
|---|---|---|
| Charger on the existing service, the calculation has room | $1,500 to $2,800 | $2,000 |
| EV energy management system (EVEMS), added | $750 to $1,500 | $1,000 |
| 100 A to 200 A upgrade, overhead | $2,500 to $5,000 | $3,800 |
| 100 A to 200 A upgrade, underground needing a trench | $5,000 to $7,000 and up | meter base and mast inside that, $500 to $1,500 |
| Panel replacement, same 100 A, for spaces only | $1,500 to $3,000 | $2,200 |
| ESA fee, charger / service change (contractor) | $92 / $92 | both lifted to the $92 minimum |
Charger, upgrade and load manager figures are researched ranges from Ontario contractor pages and Canadian price guides. One Toronto installer says a load manager avoids a panel upgrade of about $5,000 in many houses; that is their figure. HST is 13 percent on top.
Why Ontario prices are all over the map: the two answers on this page were priced very differently by the people we checked. For a load manager, a Canadian EV website said $300 to $400 installed, while Ottawa and Toronto electrical contractors said $750 to $1,500. For the upgrade, a Toronto EV installer said $2,500 to $5,000 overhead and $5,000 to $7,000 and up underground, and one GTA company printed $3,500 to $4,500 on one page and $1,400 to $1,800 on another. The low numbers leave out the labour, the meter base or the trench. Budget $1,000 for the load manager and $3,800 for an overhead upgrade, and get two or three quotes on the same written scope.
A Full Panel Is Not a Full Service
Two different things get called “my panel is full”. One is spaces: no empty slots for a breaker. The other is capacity: the house’s calculated load is already near what the service can carry. A parking lot with no empty stalls can still have a quiet road out front. A subpanel or a new panel fixes the stalls. Only the calculation tells you about the road, and the subpanel vs service upgrade page explains why a subpanel is a power bar, not a bigger wire from the street.
The calculation is Rule 8-200 of the code, and it does not add up every breaker. It counts a basic load for the size of the house, then adds the big appliances at set percentages, because they do not all run at once. The result is in watts; divide by 240 V for amps.
The Calculation on a Real Bungalow
Take a 1,200 sq ft bungalow near Midland on 100 A: 111.5 m2 on the main floor and the same again in a basement over 1.8 m high. Oil furnace, central air, a 12 kW electric range, an electric dryer and an electric tank water heater. Here is the arithmetic, in the order the code does it.
| Item | How it counts | Watts |
|---|---|---|
| Living area | 111.5 m2 main + 75 percent of 111.5 m2 basement = 195.1 m2 | |
| Basic load | 5,000 W for the first 90 m2, plus 1,000 W for each 90 m2 or part after it (105.1 m2 is two parts) | 7,000 |
| Central air, about 15 A at 240 V | 100 percent | 3,600 |
| 12 kW range | 6,000 W, nothing over 12 kW to add | 6,000 |
| Dryer 5,000 W and water heater 3,000 W | 25 percent of each, because there is a range | 2,000 |
| House without a charger | 18,600 W, but never less than 24,000 W | 24,000 (100 A) |
| Add a 32 A charger | 18,600 + 7,680 at 100 percent = 26,280 W | 109.5 A |
| Add a 16 A charger instead | 18,600 + 3,840 = 22,440 W, so the 24,000 W floor applies | 100 A |
A worked illustration of the method, not a design for your house. The furnace blower and small appliances are inside the basic load. ESA’s own bulletin example, a 140 m2 house with air conditioning, a 12 kW range, a 32 A charger, a dryer and a storage water heater, comes to 26,055 W, 108.6 A, and needs at least a 125 A service.
So on paper this bungalow cannot take a full 32 A charger on 100 A, and it can take a 16 A one. A 16 A charger adds 3.84 kW, about 20 km an hour, about 160 km in the eight cheap overnight hours. Most people commute less than that in a day. Feel free to be embarrassed about how slow it sounds; your car will not be.
What a Load Manager Does
An EV energy management system watches the current the whole house is drawing and turns the charger down, or off, when the house gets busy, then lets it back up when the range and the dryer are done. Because it can never let the charger push the service past its rating, Rule 8-106 lets the charger be counted at less than its full value, and the 2024 code recognizes energy management systems beyond the EV-only kind. In the bungalow above, a load manager is what lets the full 32 A charger in without a new service.
Rule 8-106 also allows an existing service to be evaluated using measured actual demand data when you add load. In plain words, real meter readings of what your house draws can count, not just the paper calculation. Only an LEC and ESA make that call, and the electrification load planning page covers where that helps.
Two EVs on one house is the same idea. Two chargers at full rate on 100 A is not going to calculate. Two chargers sharing through a load manager, or a pair that share one circuit, depending on the equipment, often does; for ordinary commuting both cars get what they need by morning because they take turns.
When Only 200 A Will Do
- A heat pump with electric backup is coming. Electric heat counts at 100 percent for the first 10 kW. A 10 kW backup strip, even counted in place of the air conditioner, takes the bungalow to 25,000 W, about 104 A, before the car. Upgrade once, not twice.
- A hot tub is on the list. Hot tub and spa heaters count at 100 percent. The load manager can only shuffle so much.
- The service is old as well as small. A 1960s meter base, a frayed mast or a fused panel is getting replaced anyway. Do the charger on the new service.
- You want two fast chargers at once. Then you are buying capacity, not managing it.
For the upgrade itself, what it costs and what the utility does, see the panel upgrade cost page, and the longer 100 or 200 amp page for the whole-house view. For the charger installation pricing, the EV charger cost page has it line by line.
Questions people ask
Can I install an EV charger on 100 amp service?
Often, yes. It depends on the calculated load of your house under the code, not the size of the main breaker alone. A lower-amp charger or an EV load manager makes it work in many 100 A houses; heavy electric heat or a hot tub usually means 200 A.
What is an EVEMS?
An electric vehicle energy management system. It measures what the house is drawing and limits the charger so the service is never overloaded, which lets the code count the charger at less than its full value. Installed, $750 to $1,500, about $1,000 typical.
Will a subpanel let me add a charger?
A subpanel adds breaker spaces, not capacity. If the problem is spaces, it helps. If the calculated load is already at the limit, a subpanel changes nothing.
How slow is a 16 amp charger?
About 3.8 kW, roughly 20 km of driving an hour at about 19 kWh per 100 km, or about 160 km over eight overnight hours. For most commuters that is plenty.
Who decides if my service can handle a charger?
A Licensed Electrical Contractor does the calculation and ESA inspects it. Run the numbers first with the calculator so you know what to ask.
Run the numbers on your own house
The EV charger cost calculator prices the charger, the load manager and the upgrade side by side, so you can see what each answer costs before the electrician arrives. If you have two quotes that disagree on whether you need 200 A, the $99 review reads them both and tells you which one did the calculation.
Sources and further reading
- ESA Bulletin 8-3-15: demand factors: ESA’s worked load calculation for a house with air conditioning, a range and a Level 2 charger.
- ESA Bulletin 86-1-7: electric vehicle charging systems: how an EV charger is counted in the load calculation and how an energy management system changes it.
- Ontario Electrical Safety Code: ESA on the 2024 (29th) edition in force since May 1, 2025, and what changed for houses, EV loads and energy storage.
