Typical Residential Load Wattages
| Appliance / Load | Typical Watts | Notes |
|---|---|---|
| Electric range/oven | 8,000-12,000 | NEC allows demand factor for ranges over 8.75 kW |
| Electric clothes dryer | 4,500-5,500 | Use nameplate or 5,000W minimum per NEC |
| Central A/C (3 ton) | 3,500 | Use locked rotor amps for starting surge |
| Electric water heater | 4,500 | Continuous load — apply 125% for circuit sizing |
| Dishwasher | 1,200-1,800 | Check nameplate — newer models use less |
| Washing machine | 500-800 | Motor load, brief surge on start |
| Refrigerator | 100-400 | Running watts, not starting surge |
| Microwave | 1,000-1,500 | Input watts, not cooking watts |
| General lighting + outlets | 3 W per sq ft | NEC 220.12 — minimum for dwelling units |
These are starting points. Always check the nameplate on the actual equipment. A "1500W space heater" might actually draw 1,440W — close enough for estimation, but the nameplate is the legal number for code calculations.
How NEC Demand Factors Work (Step by Step)
- Add up every connected load. This is your total connected load — the theoretical maximum if every appliance ran at full power simultaneously. A typical 2,000 sq ft house might have 30,000-45,000W connected.
- Apply the general lighting demand factor. NEC 220.42 says: first 3,000 VA at 100%, next 3,001-120,000 VA at 35%. Your 6,000W of lighting and general outlets becomes 3,000 + (3,000 x 0.35) = 4,050W demand.
- Apply appliance demand factors. Four or more fixed appliances (water heater, dishwasher, disposal, etc.) get a 75% demand factor per NEC 220.53. If your fixed appliances total 12,000W, the demand load is 9,000W.
- Apply range demand factor. A single household range up to 12 kW can use 8 kW demand per NEC Table 220.55 Column C. Your 10,000W range only counts as 8,000W for panel sizing.
- Sum the demand loads. Add up all the demand-adjusted categories. This total is what your panel and feeder must handle.
- Size the service. Divide total demand watts by 240V to get amps. Round up to the next standard panel size (100A, 150A, 200A). Most modern homes need 200A service.
This calculator applies a simplified demand factor: first 10,000W at 100%, remainder at 40%. That is a quick approximation. The full NEC method described above gives a more accurate result for permit applications. For critical panel sizing, consult a licensed electrician who can apply all applicable demand factors.
Example: Sizing a 2,000 Sq Ft Home Panel
Consider a standard 2,000 sq ft home with these major loads:
- General lighting and outlets: 2,000 sq ft x 3 W = 6,000W
- Kitchen small appliance circuits (2 required): 3,000W
- Laundry circuit: 1,500W
- Electric range: 10,000W (demand: 8,000W per NEC Table 220.55)
- Clothes dryer: 5,000W
- Water heater: 4,500W
- Dishwasher: 1,500W
- Central A/C: 3,500W
Lighting + small appliance + laundry subtotal: 10,500W. Apply NEC 220.42: first 3,000W at 100% + remaining 7,500W at 35% = 3,000 + 2,625 = 5,625W.
Fixed appliances (water heater + dishwasher + dryer = 11,000W): qualify for 75% factor = 8,250W.
Total demand: 5,625 + 8,000 (range) + 8,250 + 3,500 (A/C) = 25,375W. At 240V that is 105.7A. A 150A panel handles it, but most electricians recommend 200A for future capacity — especially if you plan to add an EV charger or battery backup.
Thinking about backing up this load with batteries during a power outage? Our UPS battery backup calculator shows how long your battery bank would last under this kind of demand.
Worked Examples
Sizing a Sub-Panel for a Home Addition
Context
You are adding a bedroom suite with a 1,500W bathroom heater, two 1,200W window AC units, and general lighting/outlet loads of 3,000W. You need to determine if a 60A sub-panel is adequate.
Calculation
Connected load: 1,500 + (2 x 1,200) + 3,000 = 6,900 W
At 240V single-phase: 6,900 / 240 = 28.8 A connected
NEC demand factor (first 10 kVA at 100%): 6,900 W = 6.9 kVA at 100% = 6,900 W demand
Demand amps: 6,900 / 240 = 28.8 A
Interpretation
The 28.8A demand load fits well within a 60A sub-panel. You have headroom for future loads like a second heater or a mini-split.
Takeaway
Connected load alone does not tell the full story — NEC demand factors reduce the effective load on larger panels. For the wire run to this sub-panel, check our wire distance calculator to ensure you use heavy enough cable for the distance.
Checking if a 200A Panel Handles a New EV Charger
Context
Your home's existing loads total 18 kW connected. You want to add a Level 2 EV charger rated at 7.2 kW (240V, 30A). The panel is rated 200A at 240V.
Calculation
Existing connected: 18,000 W
New EV charger: 7,200 W
Total connected: 25,200 W
NEC demand (first 10 kVA at 100%, remainder at 40%): 10,000 + (15,200 x 0.40) = 10,000 + 6,080 = 16,080 W
Demand amps: 16,080 / 240 = 67 A
Interpretation
At 67A demand, you are well within the 200A panel capacity. The NEC demand factor method shows the panel can handle the charger even though connected load is 25 kW.
Takeaway
EV charger loads are continuous (running 3+ hours), so NEC requires the circuit to be sized at 125% of the charger's rated current. Estimate the charger's monthly cost with our kWh calculator before committing to a charging schedule.
Frequently Asked Questions
Glossary
Connected Load
The total wattage of all electrical devices that could potentially run at the same time on a circuit or panel. This is always higher than the actual demand load because not everything runs simultaneously.
Demand Factor
The ratio of actual expected load to total connected load, expressed as a percentage. NEC provides standard demand factors for residential calculations — typically 100% for the first 10 kVA, then 40% for the remainder.
Continuous Load
Any load expected to run for 3 hours or more without interruption. NEC requires continuous loads to be sized at 125% of their rated current, which affects breaker and conductor sizing.
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This calculator gives you a quick demand estimate for planning purposes. The actual NEC load calculation for a permit application involves more specific demand factors per appliance category, and your local jurisdiction may have amendments. For new construction or panel upgrades, a licensed electrician can run the full Article 220 calculation and ensure your service meets code. These results are estimates — actual demand varies with usage patterns and equipment.
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Written and maintained by Dan Dadovic, Developer & Off-Grid Energy Enthusiast. On the energy side, Dan has hands-on experience with residential solar panel installation, DIY battery bank construction, off-grid power systems, and wind power — all from building and maintaining his own systems..
Disclaimer: Calculator results are estimates based on theoretical formulas. Actual performance varies with temperature, battery age, load patterns, and equipment condition. For critical electrical work, consult a licensed electrician.