Add dryers, storage-type water heaters, and any other fixed appliance rated over 1500 W (not already entered above).
📄 Minimum Service Size
Load Breakdown
Full Calculation Table (CEC Rule 8-200)
| Item | Rule Reference | Load (W) |
|---|
How to Use the Electrical Load Calculation
Use the area per CEC Rule 8-110, generally excluding unfinished basement space.
Enter 0 for any load that doesn't apply, such as a gas furnace with no electric space heating.
List dryers, storage water heaters, and any other fixed appliance over 1500 W not already entered above.
The calculator applies the full CEC Rule 8-200(1)(a) formula and returns the calculated load and minimum service ampacity.
How CEC Rule 8-200 Calculates Dwelling Load
Rule 8-200 is the standard method for determining minimum service or feeder size for a single dwelling, defined as a detached house or one unit of row housing, a semi-detached, duplex, triplex, or quadruplex. It builds the calculated load piece by piece, starting with general lighting and receptacles and adding major appliances with their own specific demand factors.
The Basic Load: Area-Based Lighting and Receptacles
The basic load starts at 5000 W for the first 90 square metres of living area, with an additional 1000 W for each additional 90 square metres or portion thereof. A 180 m² home, for example, lands at 6000 W: the initial 5000 W plus 1000 W for the second 90 m² block. This basic load covers general lighting and receptacle circuits, not major appliances, which get added separately with their own rules.
Space Heating, Air Conditioning, and the Interlock Rule
Electric space heating is added at full connected load under this rule, and air conditioning or heat pump load is added per Rule 8-106(3). If heating and cooling are electrically interlocked so they can never run simultaneously, only the larger of the two needs to be counted rather than both added together, since the building will never draw both loads at once.
The Range, Water Heater, and EV Charging Rules
A single electric range is calculated at 6000 W, plus 40% of any amount the range's actual rating exceeds 12 kW. Tankless water heaters and water heaters for steamers, pools, hot tubs, and spas count at full 100% demand. EV charging equipment also counts at 100% demand under this rule, even though Section 86 treats EV charging as a continuous load in other contexts, since Rule 8-200(2) specifically excludes this load from being treated as continuous for dwelling service sizing purposes.
The Catch-All Rule for Everything Else Over 1500 W
Every other fixed appliance rated over 1500 W, like a clothes dryer or a storage-type electric water heater, gets added using a final catch-all rule. If an electric range has been provided for, each of these additional loads counts at 25% of its rating. If no electric range exists, the rule shifts to 100% of the combined additional load up to 6000 W, plus 25% of any amount beyond that 6000 W threshold.
The Floor-Area Minimum Service Size
Regardless of how the calculated load comes out, CEC Rule 8-200(1)(b) sets an absolute floor: a 100 A minimum service when the dwelling's floor area, excluding the basement, is 80 square metres or more, and a 60 A minimum when it's smaller than that. A dwelling with a very low calculated load still can't use a service smaller than these minimums.
Next Steps
If the calculated load shows the existing service is insufficient for planned new equipment, the service entrance calculator covers the augmented load method for adding equipment to an existing service. The electrical load schedule tool helps organize the resulting circuits once the service size is confirmed.
Frequently Asked Questions
The basic load is 5000 W for the first 90 square metres of living area, plus an additional 1000 W for each additional 90 square metres or portion thereof. This basic load covers general lighting, receptacle circuits, and similar loads, and is the starting point before adding space heating, air conditioning, the range, and other major appliances.
CEC Rule 8-200(1)(b) sets a 100 amp minimum service ampacity when the dwelling's floor area, excluding the basement, is 80 square metres or more, and a 60 amp minimum when the floor area is less than 80 square metres. The calculated load from the full Rule 8-200 calculation can require a larger service than this minimum, but the service can never be smaller than these floor-area-based minimums regardless of how low the calculated load comes out.
Yes, as long as each unit is being calculated individually and has its own separate service or feeder, since CEC's definition of single dwelling specifically includes one unit of row housing, semi-detached, duplex, triplex, or quadruplex housing. If a single main service supplies two or more dwelling units together, Rule 8-202 applies instead, which uses a different stepped demand factor method.
An electric range is usually the single largest appliance load in a home, so its presence already adds significant demand to the calculation. When no electric range exists, the code compensates by allowing more generous treatment of other large appliances, applying 100% demand up to 6000 W combined rather than the stricter 25% per-appliance factor used when a range is already part of the calculation.
Related HVAC Tools
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