Home Generator Sizing & Transfer Switch Calculator
Homeowners preparing for power outages and storm backup. Interactive whole-house appliance checklist (refrigerator, well pump, sump pump, AC, furnace blower, lights, microwave) calculating continuous and surge watts, recommended generator kW, and inlet box size (30A vs 50A).
Step-by-Step Derivation ▼ Show Steps
Calculations adhere to standard electrical engineering physics and National Electrical Code (NFPA 70) regulations.
Engineering Principles & Calculations
This calculator uses the exact mathematical relationships between Checklist of Household Appliances with Starting/Running Wattages to determine Total Running Watts, Peak Surge Watts, Recommended Generator Size (kW), Transfer Switch Amps (30A, 50A, 100A, 200A). In practical installations, factors such as ambient raceway temperature, harmonic distortion, duty cycle continuous operation, and conductor impedance must be accounted for by a certified electrician.
Interactive whole-house appliance checklist (refrigerator, well pump, sump pump, AC, furnace blower, lights, microwave) calculating continuous and surge watts, recommended generator kW, and inlet box size (30A vs 50A).
Typical Application & Industry Guidelines
Homeowners preparing for power outages and storm backup.
Home Generator Sizing & Transfer Switch Calculator Benchmark Lookup Table
| Household Appliance | Average Running Watts | Starting Surge Watts | Priority Level |
|---|---|---|---|
| Refrigerator / Freezer | 600 Watts | 1,800 Watts | Critical Essential |
| Well Pump (1/2 HP - 1 HP) | 1,200 Watts | 3,500 Watts | High Essential |
| Sump Pump (1/3 HP) | 800 Watts | 2,100 Watts | Critical Essential |
| Furnace Fan Blower | 600 Watts | 1,500 Watts | High Essential (Winter) |
| Central AC (3-Ton) | 3,500 Watts | 7,500 Watts | Comfort Load |
| Electric Water Heater | 4,500 Watts | 4,500 Watts (0 surge) | High Draw (Manage Manually) |