📊 Demand Reduction
Demand Factor Breakdown
Full Calculation Table
| Load Component | Demand Factor | Demand Load |
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How to Use the Demand Factor Calculator
Space heating, multi-unit dwelling loads, and commercial basic loads each follow a different CEC demand factor structure. Choose the one that matches your calculation.
Use the equipment's actual nameplate rating or the connected load from your design drawings, not an estimate.
The calculator applies the relevant CEC demand factor breakpoints and shows the resulting calculated demand load for service or feeder sizing.
Understanding CEC Demand Factors
A demand factor is the ratio between the load you actually expect a service or feeder to carry at any given moment and the full connected load of everything attached to it. Almost no building runs every light, receptacle, and piece of equipment at full capacity simultaneously, so the CEC allows demand factors that reflect decades of measured real-world electrical usage. Applying the right demand factor keeps service and feeder sizing realistic instead of wastefully oversized.
Electric Space Heating Demand
For a single dwelling, electric space heating is generally calculated at 100% of the connected load, since heating in a house tends to run close to full capacity during the coldest part of the year. For other occupancies like commercial and industrial buildings, the first 10 kW of connected heating load is taken at 100% demand, and any heating load beyond that 10 kW threshold drops to 75% demand. If the heating and air conditioning systems are interlocked so they never run at the same time, CEC Rule 8-106(3) lets you count only the larger of the two loads rather than adding them together.
Multi-Unit Dwelling Demand
When a single service or feeder supplies two or more dwelling units, such as an apartment building or row housing, CEC Rule 8-202(3)(a) applies a stepped demand factor: the unit with the heaviest load counts at 100%, the next unit counts at 65%, and each additional unit beyond that follows further reduced demand factors. This reflects the reality that not every unit in a building draws its peak load at the same instant. Space heating, air conditioning, and EV charging loads are excluded from this stepped calculation and added separately with their own demand factors.
Commercial Basic Load Demand
For commercial and other occupancies covered by CEC Rule 8-210 and Table 14, the basic load is calculated from floor area and a watts-per-square-metre density specific to the occupancy type, typically in the range of 25 to 30 W/m² for offices and retail stores. A demand factor from Table 14, commonly somewhere between 70% and 100% depending on the specific occupancy classification, is then applied to that basic load. Special loads like motors, water heaters, and other named equipment in Rule 8-210(b) are generally added on top at full demand rather than being folded into the basic load's reduced percentage.
Confirm Your Specific Demand Factor
CEC Table 14 lists demand factors by specific occupancy classification, and the exact percentage varies by building type. This calculator uses reasonable default values you can adjust, but always confirm the exact Table 14 percentage for your occupancy classification against the current CEC edition adopted in your province before finalizing a service size. For dwelling-specific calculations beyond this tool's scope, the electrical load calculation tool covers a fuller breakdown of connected building load.
Next Steps
Once you have a calculated demand load, use the service entrance calculator to confirm minimum service size, and the electrical load schedule tool to break the demand down circuit by circuit for panel scheduling.
Frequently Asked Questions
For a single dwelling, electric space heating is generally calculated at 100% of the connected load. For other occupancies such as commercial and industrial buildings, the first 10 kW of electric space heating is taken at 100% demand, and any amount beyond that is taken at 75% demand, provided the heating and air-conditioning loads aren't both running at the same time, in which case only the larger of the two loads needs to be counted.
Demand factors exist because not every piece of connected equipment runs at full capacity at the exact same moment. A building's lighting, receptacles, and equipment have natural diversity in when they're actually drawing power, so sizing a service for 100% of every connected watt would oversize the equipment and waste money. The CEC's demand factors reflect decades of measured data on how buildings actually use electricity, letting you size services and feeders closer to real-world demand while staying safe.
CEC Rule 8-202(3)(a) applies a stepped scale: the dwelling unit with the heaviest load counts at 100% demand, the unit with the same or next smaller load counts at 65%, and additional units follow further reduced percentages from there. Space heating, air conditioning, and EV charging are excluded from this stepped scale and calculated separately with their own demand factors before being added to the total.
CEC Rule 8-106(9) allows the use of a demonstrated load, meaning historical maximum demand data recorded over at least 24 months for a similar facility, instead of the calculated load, but only when the calculation is performed by a qualified person as recognized by the authority having jurisdiction. This isn't a substitute for a proper calculation in most everyday situations and generally applies to larger commercial or institutional projects with an engineer involved.
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