What the City of Calgary actually asks for
When you take out an electrical permit for a secondary suite in Calgary, the City requires a completed secondary suite electrical load calculation. It is a one-page worksheet that adds up the connected load of the house and the suite, applies the demand factors from the Canadian Electrical Code, and produces a single number in amps that gets compared against your existing service.
The point is simple: the City wants documented evidence that a 100 A service isn't about to be asked to carry two kitchens, two ranges, electric heat and an EV charger.
The official form and the current secondary suite requirements live on the City's own pages — Add a new secondary suite and the secondary suite load calculation PDF. Always pull the form fresh from calgary.ca rather than reusing an old copy, since the City revises it periodically.
Calgary wants the completed calculation before the electrical rough-in inspection, submitted by email to the electrical inspection group. In practice you want it done far earlier than that — at rough-in, the walls are open and the service is already installed. If the calculation says you needed a bigger service, finding out at rough-in is the expensive way to learn it.
How the calculation works under CEC Rule 8-200
Rule 8-200 of the Canadian Electrical Code sets out the calculated load for a single dwelling. The structure is the same whether you're doing it on the City's form or in a calculator:
1. Basic load from floor area
Every dwelling unit starts with a floor-area allowance that covers general lighting, receptacles, the small-appliance circuits, laundry and similar:
| Living area | Basic load |
|---|---|
| First 90 m² (about 968 ft²) | 5000 W |
| Each additional 90 m², or portion of it | 1000 W |
Living area is measured per dwelling unit. How basement area counts depends on whether it's finished living space and how the suite is laid out — this is one of the places DIY calculations most often go wrong.
2. Add the major connected loads
On top of the basic load, you add the equipment that actually moves the needle:
- Space heating and air conditioning — with interlocked heating and cooling handled so you don't double-count
- Electric range — per unit
- Tankless or instantaneous water heaters — these are large and frequently missed
- Hot tub or spa
- EV charging equipment — counted at 100% of its rating unless load management is installed
- Any other significant fixed appliance
3. Apply demand factors across the two units
This is the part that surprises people. The Code does not simply add the two dwelling units together. Because two households rarely peak at the same moment, demand factors reduce the contribution of the smaller unit — the largest unit's basic demand counts in full, and subsequent units count at a reduced percentage. Loads that don't diversify, such as EV charging, are added at full value afterward.
The practical effect: a house and suite that look like they add up to 180 A of connected load may calculate out well under 100 A once the demand factors are applied. This is exactly why running the calculation before assuming you need an upgrade is worth the ten minutes.
Run the Calgary calculation free
Our calculator applies Rule 8-200 demand factors line by line, shows every step, and generates a completed City of Calgary load calculation form PDF from the same numbers.
Start the free calculator →Minimum service size, regardless of the math
Even if your calculated demand is low, the Code sets a floor on service size. For a single dwelling with a floor area of 80 m² or more (excluding basement), the minimum service ampacity is 100 A. Below 80 m², 60 A is the minimum permitted. In practice, virtually every Calgary house with a legal suite is on 100 A or larger.
What to do if the number comes in over your service
If the calculation exceeds your existing service, you have real options before jumping to a service upgrade:
- Change the equipment. Swapping a tankless electric water heater for gas, or an electric range for gas in the suite, can move the number substantially.
- Add load management. If EV charging is what pushed you over, an EVEMS (electric vehicle energy management system) lets the charger back off when the rest of the house is drawing. This is often dramatically cheaper than a service upgrade.
- Upgrade the service. Sometimes it's genuinely the right answer. Note that a service size change brings ENMAX into the process alongside the City, which adds lead time — another reason to run the numbers early.
Forgetting the suite's range entirely; using nameplate watts for the heating and the A/C when they're interlocked; leaving out a tankless water heater; measuring floor area in square feet and entering square metres; and using a stale copy of the City form. Any of these will get the calculation bounced.
Frequently asked questions
When is the Calgary secondary suite load calculation due?
Before the electrical rough-in inspection on your permit. Earlier is better — the result determines whether the existing service is adequate, and that decision affects everything downstream.
Who is responsible for completing it?
Normally the electrical contractor holding the permit. If you're working under a homeowner's permit, it's on you. Either way the figures need to reflect the actual connected loads in both units.
Does a secondary suite always mean a service upgrade?
No. Many Calgary homes carry a suite on an existing 100 A service once demand factors are applied. It depends on combined calculated demand, not on unit count.
Does this apply to laneway and backyard suites too?
Yes — the same principle applies to any added dwelling unit on the service, though the form fields and addressing differ. Our calculator handles SFD, secondary suite and laneway suite combinations.
Want a master electrician to check it?
If the result lands close to your service limit, or it's going to the City on a permit, we can review the calculation and walk through your options before you spend money.
Get it signed off →This guide is general information for planning purposes, not a substitute for a permit submission or a code ruling. Requirements change and final acceptance always rests with the authority having jurisdiction. Confirm current requirements at calgary.ca.