Electrical Load Calculator
Calculate total electrical load in amps and compare to panel capacity. Identify circuits close to capacity.
⚡ Construction📐 Total Load (Amps) = Total Watts / Voltage
HVAC/AC load (watts)
Lighting load (watts)
Appliance load (watts)
General receptacle load (watts)
Panel voltage (120 or 240)
Please enter valid values.
Formula & Reference
| Variable | Formula | Units |
|---|---|---|
| Electrical Load Calculator | Total Load (Amps) = Total Watts / Voltage | Amps |
Step-by-Step Examples
Example 1
Typical Home
5,000W HVAC, 1,200W lighting, 3,500W appliances, 1,800W receptacles.
- Total: 11,500W / 240V = 47.9A
- = 47.9% of 100A panel | 24% of 200A panel
✓ 47.9 amps
Example 2
High-Load Home
8,000W HVAC, 2,000W lighting, 5,000W appliances.
- Total: 15,000W / 240V = 62.5A
- = 62.5% of 100A | 31% of 200A
✓ 62.5 amps
Example 3
Small Apartment
2,000W HVAC, 800W lighting, 2,000W appliances.
- Total: 4,800W / 120V or 240V
- 240V: 20A | 120V: 40A
✓ 20 amps at 240V
Real-World Applications
Electricians
Calculate panel load before adding circuits.
Contractors
Estimate panel upgrade need during renovations.
Homeowners
Determine if your electrical panel has sufficient capacity.
Estimators
Quick electrical load estimate for project bids.
Common Mistakes to Avoid
⚠️
Running at over 80% capacity
NEC 210.20 requires circuits to run at no more than 80% of rating for continuous loads (3+ hours). A 100A panel should not exceed 80A in continuous use.
⚠️
Adding large appliances without panel check
Adding EV charger (30-50A), hot tub (50A), or second HVAC unit without checking total panel load can cause breakers to trip or worse.
Frequently Asked Questions
When do you need a 200A service? ▾
Modern homes with HVAC, EV chargers, electric ranges, and electric water heaters typically need 200A service. A 100A service was sufficient for older, less electric-dependent homes.
How to calculate service panel size needed? ▾
Add up all loads at nameplate ratings. Apply NEC demand factors (you don't count 100% of all loads simultaneously). The NEC Article 220 method provides the standard calculation.
What permits are needed? ▾
Any new electrical panel, new circuit, or service upgrade requires permits and inspection in all jurisdictions. Never skip permits on electrical work.