Electrical Load Calculator (NEC Article 220)
Calculate the total demand load and recommended service size for a panel. Add lighting, appliance, HVAC, and other loads — and the calculator applies NEC Article 220 demand factors to return the demand current and the next standard service size.
Total demand
17.58kVA
Demand current
73.2A
Service size
100A
A 100 A service covers this load
General load after 220.42 demand factor: 4575 VA · Appliance demand: 0 VA · Largest HVAC: 5000 VA.
Simplified NEC Article 220 standard method. Optional and feeder/sub-panel methods are available in the Voltix app.
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How the load calculation works
NEC Article 220 doesn't simply sum every nameplate watt. It applies demand factors that reflect the reality that not every load runs at full power simultaneously. The standard method applies category-by-category factors:
- General loads— lighting (3 VA/sq ft), receptacles, small-appliance circuits (1,500 VA each, minimum 2 required), and the laundry circuit (1,500 VA) all combine and get the Table 220.42 demand factors.
- Fixed appliances — taken at 75% of nameplate when four or more are present (NEC 220.53).
- Heating and air conditioning — only the larger of the two is counted (NEC 220.60).
- Range— derated per NEC Table 220.55 (typically 8 kVA for a single household range up to 12 kW).
- EV charger — added at 100% of the circuit VA.
From VA to service size
Convert the total demand VA to amps by dividing by the service voltage. For a single-phase 240 V service: amps = VA ÷ 240. Round up to the next standard service size: 100, 125, 150, 200, 225, 300, 400 A.
Worked example — standard method
A 1,800 sq ft home with: electric range (12 kW nameplate), dryer (5.5 kW), electric water heater (4.5 kW), dishwasher (1.2 kW), garbage disposal (0.9 kW), 5-ton central A/C (7.2 kVA demand), and two small-appliance circuits.
- General lighting: 1,800 × 3 = 5,400 VA
- Small appliance + laundry (3 circuits): 3 × 1,500 = 4,500 VA
- Table 220.42 on 9,900 VA: 3,000 + (6,900 × 0.35) = 5,415 VA
- Range (Table 220.55): 8,000 VA
- Dryer: 5,500 VA
- Water heater + dishwasher + disposal = 6,600 VA × 75% = 4,950 VA (4 appliances)
- A/C (larger of A/C vs heating): 7,200 VA
- Total demand: 5,415 + 8,000 + 5,500 + 4,950 + 7,200 = 31,065 VA
- Service amps: 31,065 ÷ 240 = 129.4 A → 150 A service
When to choose a 200 A service
The calculated load for many homes falls between 100 A and 175 A, but specifying 200 A is common practice for several reasons: the cost difference between 150 A and 200 A is small; future loads (EV charging, heat pumps, additional HVAC) are difficult to predict at design time; and the NEC does not require you to install the minimum calculated service if you choose a larger one. For new homes in 2024 and beyond, a 200 A minimum is essentially industry standard.
Who is this calculator for?
Used by electricians and electrical designers performing NEC Article 220 load calculations for new residential services, panel upgrades, and commercial feeders. Particularly useful when determining whether an existing 100 A or 150 A service can handle added loads such as an EV charger, hot tub, electric vehicle charging, or additional HVAC. Always verify against the current edition of the NEC and local amendments before submitting for permit.
Frequently Asked Questions
- What demand factor applies to general lighting load?
- Under NEC Table 220.42, the first 3,000 VA of combined general lighting, receptacle, small-appliance, and laundry load is taken at 100%; the next 117,000 VA at 35%; and anything above 120,000 VA at 25% for dwelling units.
- Do I add air conditioning and heating loads together?
- No. NEC 220.60 allows you to omit the smaller of two non-coincident loads — heating and air conditioning won't run simultaneously at full load. Use only the larger of the two in your calculation.
- When can I apply the 75% appliance demand factor?
- NEC 220.53 permits a 75% demand factor when four or more fixed appliances (other than range, dryer, HVAC, and space heating) are on the same feeder or service. Common examples: dishwasher, garbage disposal, water heater, and microwave.
- What service size do I need for a typical home?
- Most modern single-family homes calculate out to 100–150 A under the standard method. Larger homes with electric heat, EV charging, or a workshop may require 200–400 A. The NEC does not prescribe a minimum — the load calculation determines the size.
- What is the optional method (NEC 220.82) and how does it differ?
- The optional method for single-family dwellings uses a single demand factor: 100% of the first 10 kVA of total load, then 40% of the remainder. It often results in a smaller calculated service than the standard method, and is only available for dwellings with a 100 A or larger service.
- How does an EV charger affect the service calculation?
- A Level 2 EV charger (240 V, 48 A circuit) adds 11,520 VA at 100% to the load calculation under NEC 220.57 (2023 NEC). This is one of the main reasons newer homes are moving from 200 A to 320 A or 400 A services — an EV charger combined with electric HVAC and a range is a genuinely high combined load.
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