NEC Panel Load Calculator
Current Panel
Existing Loads
AC Size
Planned Additions
EV Charger
Heat Pump
0 kW
Panel Verdict
Panel Sufficient
Total Connected Load31,700 W
NEC 220.40 Demand28,275 W
NEC 220.82 Demand18,680 W
Standard Load (Amps)117.8 A
Optional Load (Amps)77.8 A
Headroom+82.2 A
220.40 Utilization
58.9%
of 200A panel220.82 Utilization
38.9%
of 200A panelLoad Breakdown
| Load | Connected (W)↕ | Status |
|---|---|---|
| Central AC (3 ton) | 3,800 | Existing |
| Electric Range | 12,000 | Existing |
| Electric Dryer | 5,400 | Existing |
| Electric Water Heater | 4,500 | Existing |
| General Lighting + Receptacles | 6,000 | Existing |
This NEC panel load calculator estimates the electrical service demand of a dwelling and tells you whether your existing panel can absorb new loads like an EV charger, heat pump, or induction range. It runs both the NEC 220.40 standard method and the 220.82 optional method, converts demand watts to amps at 240 V, and applies the 80% continuous-load rule to flag when a service upgrade is needed.
Formula
Demand amps = Demand watts ÷ 240 V; Optional demand = 10,000 + 0.40 × (connected − 10,000)
- connected
- Total connected nameplate load in watts (VA) across all appliances and lighting
- Optional demand
- NEC 220.82 demand: first 10 kVA at 100%, remainder at 40%
- 240 V
- Single-phase residential service voltage used to convert watts to amps
- 80% rule
- An upgrade is flagged when demand amps exceed 80% of the panel rating
How it works
- Describe your existing loads: central AC tonnage, electric range, dryer, water heater, and the conditioned square footage used for general lighting and receptacle demand at 3 VA/sq ft.
- Add planned additions such as a Level 1/2 EV charger, a heat pump, a heat-pump water heater, an induction range, or solar PV. Each appliance pulls a nameplate wattage from the NEC load tables.
- The calculator computes the standard-method demand (lighting demand factors, NEC 220.55 range demand, other loads at nameplate, plus 25% of the largest motor) and the optional-method demand (first 10 kVA at 100%, remainder at 40%), then sizes the panel against your current rating.
Worked example
A home with an electric range, electric dryer, electric water heater, 2,000 sq ft of lighting, adding a 48 A Level 2 EV charger on a 200 A panel.
- Connected load = range 12,000 + dryer 5,400 + water heater 4,500 + lighting (2,000 × 3 = 6,000) + EV 11,520 = 39,420 W.
- Standard method: lighting demand factors + range demand (NEC 220.55) + other loads at nameplate + 25% of the largest motor ≈ 37,925 W → 158 A.
- Optional method: 10,000 + 0.40 × (39,420 − 10,000) ≈ 21,768 W → about 91 A.
- Highest method = 158 A; 80% of a 200 A panel is 160 A, so 158 A still fits.
Standard-method demand is about 158 A (79% of the 200 A panel), no upgrade is required, and the recommended service remains 200 A.
Frequently asked questions
- What is the difference between the standard and optional methods?
- The NEC 220.40 standard method applies individual demand factors to lighting, ranges, and motors. The NEC 220.82 optional method is a simpler whole-house calculation that takes the first 10 kVA at 100% and the rest at 40%. This tool runs both and uses the higher result for the upgrade decision.
- Why does the calculator use 80% of my panel rating?
- The NEC limits continuous loads to 80% of a breaker or service rating. So a 200 A panel is treated as having about 160 A of usable continuous capacity, and an upgrade is recommended when calculated demand exceeds that threshold.
- Can my panel handle an EV charger?
- It depends on your existing demand and the charger amperage. A 48 A Level 2 charger adds roughly 11.5 kW (about 48 A at 240 V), which can push a loaded panel past the 80% limit. Enter your appliances and the charger level to see the calculated headroom in amps.
- Is this a substitute for a licensed electrician?
- No. This is a planning estimate based on standard NEC tables and typical nameplate values. A licensed electrician must perform the official load calculation and pull permits before any service upgrade or new circuit installation.