Electrical Load Calculator
Minimum service size for a single dwelling per CEC Rule 8-200 — the greater of Option A and Option B, with an NEC mode, every constant cited and the math shown.
This tool estimates calculated load per CEC Rule 8-200 for guidance only. Final design must be verified by a licensed electrician and approved by the local authority having jurisdiction. Provincial amendments (e.g. BC, Ontario, Alberta) may differ.
This tool estimates calculated load per CEC Rule 8-200 for guidance only. Final design must be verified by a licensed electrician and approved by the local AHJ. Provincial amendments may differ.
Single dwelling
Minimum service size
100 A
- Calculated load
- 24,000 W
- Calculated current
- 100 A
- Governing method
- Option B (area)
- Flat alternative minimum (area ≥ 80 m²)
- 24,000 W
- This tool estimates calculated load per CEC Rule 8-200 for guidance only. Final design must be verified by a licensed electrician and approved by the local AHJ. Provincial amendments may differ.
- Option B governs — the calculated load is the greater of Option A (16,630 W) and Option B (24,000 W).
- Based on CEC 26th edition (CSA C22.1:24), Canada (CEC base).
How this is calculated
Basic load — 8-200(1)(a)(i)
5000 W (first 90 m²) + 1000 W × blocks of 90 m² above
= 5000 + 1000 × ceil(max(0, 185.8 − 90) ÷ 90)
7,000 W
Space heating + A/C — 8-200(1)(a)(ii) / Section 62 / 8-106(3)
heating: 100% of first 10000 W + 75% of remainder; A/C at 100%; interlock takes the larger
= heat 0 W, A/C 2,880 W, interlocked = no
2,880 W
Electric range — 8-200(1)(a)(iii)
6000 W; if rating > 12 kW add 40% of the excess
= range = 12 kW
6,000 W
Tankless/pool/spa water heater + EVSE — 8-200(1)(a)(iv), (a)(v)
tankless / pool / spa water heaters and EVSE at 100% (EVSE may use the EVEMS-limited demand)
= tankless WH 0 W + EVSE 0 W
0 W
Additional loads > 1500 W — 8-200(1)(a)(vi)
25% of each additional load (electric range installed); a storage-tank water heater is an additional load
= additional loads {3,000} W
750 W
Option A total — 8-200(1)(a)
basic + heating/AC + range + tankless WH + EVSE + additional loads
= 7,000 + 2,880 + 6,000 + 0 + 0 + 750
16,630 W
Option B — 8-200(1)(b) flat alternative minimum
24000 W if area ≥ 80 m², else 14400 W — nothing is added on top
= area 185.8 m²
24,000 W
Greater of A/B → current → service size
max(A, B) ÷ 240 V, then next standard size
= 24,000 ÷ 240 = 100 A → standard sizes {60, 100, 125, 150, 200, 225, 400}
100 A service
How to do a CEC load calculation for a single dwelling
CEC Rule 8-200(1) sizes a single-dwelling service as the greater of two options. Take a 200 m² home with a 12 kW range and a 2,880 W air conditioner. Option A (itemized) is a 5,000 W basic load for the first 90 m², plus 1,000 W for each additional 90 m² (here 2,000 W), plus 2,880 W for the A/C and 6,000 W for the range — 15,880 W. Option B is a flat alternative minimum of 24,000 W (because the area is 80 m² or more) — nothing is added on top of it. Option B is greater, so the calculated load is 24,000 W ÷ 240 V = exactly 100 A, a 100 A service.
8-200(1)(a) vs 8-200(1)(b): which option governs?
Option A itemizes every load — the area basic load, space heating and A/C (with Section 62 demand factors and the 8-106(3) interlock), the range, tankless / pool / spa water heaters and EV charging at 100%, and any additional load over 1,500 W at its demand factor: 25% each when an electric range is installed, otherwise 100% of the first 6,000 W combined plus 25% of the excess (a storage-tank water heater is an additional load). Option B is a flat alternative minimum — 24,000 W when the living area is 80 m² or more, or 14,400 W when it is under 80 m². Nothing is added to it. You must size the service to whichever option produces the larger calculated load — in practice Option B acts as a 100 A floor for average homes, and Option A governs once heavy loads (electric heat, EV charging) push the itemized total past it.
Determining living area (Rule 8-110)
Living area drives the basic load, so measure it the way the code does. Count the ground floor and all above-grade floors at 100%. Count a basement only where the finished ceiling height exceeds 1.8 m, and then at 75% of its area. Exclude unheated, unfinished or crawl spaces.
Standard service / panel sizes
| Service size | Typical use |
|---|---|
| 60 A | Small or older dwellings (legacy) |
| 100 A | Most single dwellings without electric heat |
| 125 A | Dwellings with A/C, EV charging or modest electric heat |
| 150 A | Larger homes with several heavy loads |
| 200 A | All-electric homes, electric heat plus EV charging |
| 225 A / 400 A | Large all-electric homes or multiple heavy loads |
Electric range load — CEC 8-200(1)(a)(iii)
| Range nameplate | Calculated load |
|---|---|
| ≤ 12 kW | 6,000 W |
| 14 kW | 6,800 W |
| 16 kW | 7,600 W |
| 18 kW | 8,400 W |
How an EV charger changes your load
Electric-vehicle supply equipment is added at 100% of its rating — a 48 A charger is roughly 11,520 W, which alone is about 48 A of calculated current and can push a 100 A service over the line. An energy-management system (EVEMS, Rule 8-106(10)) can cap the demand it adds, often letting an existing service stay compliant. Enter the EVEMS-limited value when one is installed.
Common load-calculation mistakes
- •Adding loads on top of Option B. 8-200(1)(b) is a flat alternative minimum — compare the itemized Option A against the bare 24,000 W / 14,400 W figure; heating, water heating and EV charging belong only in Option A.
- •Counting a storage-tank water heater at 100%. With an electric range installed, additional loads over 1,500 W — including a storage water heater — take a 25% demand factor. Only tankless, pool and spa heaters count at 100%.
- •Adding interlocked heating and A/C together. Rule 8-106(3) lets you count only the larger when they cannot run at once.
- •Using a stale code edition or ignoring provincial amendments. The constants differ by edition and by province.
- •Treating the result as a final design. It is an estimate — a licensed electrician and the AHJ must verify before any work.
Frequently asked questions
How do I calculate the electrical load for a house?+
Per CEC Rule 8-200(1), size a single dwelling on the greater of two options. Option A itemizes a 5,000 W basic load (first 90 m²) plus 1,000 W per additional 90 m², space heating/AC (Section 62 demand, 8-106(3) interlock), the range, tankless/pool/spa water heaters and EV charging at 100%, and additional loads over 1,500 W at demand factors (25% each when an electric range is installed). Option B is a flat alternative minimum — 24,000 W (≥80 m²) or 14,400 W (<80 m²) with nothing added on top. Divide the larger total by 240 V and round up to the next standard service size.
What size electrical service do I need?+
Take the calculated load in watts, divide by 240 V to get amps, then round up to the next standard size: 60, 100, 125, 150, 200, 225 or 400 A. Most modern single dwellings land on 100 A or 125 A; all-electric homes with heating and EV charging often need 200 A.
How is an electric range counted in a load calculation?+
CEC 8-200(1)(a)(ii) counts a single range as 6,000 W, plus 40% of any amount by which its nameplate exceeds 12 kW. A 14 kW range is 6,000 + 0.40 × 2,000 = 6,800 W.
Does this replace a licensed electrician?+
No. This is an estimating aid only. The final service design must be calculated and verified by a licensed electrician and approved by the authority having jurisdiction. Provincial amendments may change the constants used.
Methodology & sources
The single-dwelling calculation implements CEC Rule 8-200(1): the greater of the itemized Option A (8-200(1)(a)) and the flat alternative minimum of Option B (8-200(1)(b)). Space-heating demand uses the Section 62 factors and the 8-106(3) interlock; the electric range, tankless water heaters, EV charging and additional loads follow the rule's demand factors, including the 25% factor on additional loads when a range is installed. Every constant — 5,000 W, 1,000 W, 6,000 W, the 12 kW threshold, the 40% factor, 24,000 W / 14,400 W and the standard service sizes — lives in a versioned dataset keyed to the code edition, so a code change is a data change, not a logic change.
The NEC mode implements the Article 220.82 optional dwelling calculation with its own cited constants. Both modes are estimating aids only. A licensed electrician must verify the final design, and the authority having jurisdiction must approve it; provincial and local amendments may differ.
- CSA C22.1:24 Canadian Electrical Code, Part I (26th edition) — Rule 8-200(1) single-dwelling calculated load, Rule 8-106(3) interlock, Section 62 space-heating demand — verified July 2, 2026
- NFPA 70 National Electrical Code (NEC) 2023 — Article 220.82 Optional dwelling-unit calculation — verified July 2, 2026
Last reviewed June 28, 2026. Estimates are indicative — verify against current product specs and local requirements before ordering.
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