Generator Wattage Calculator
Calculate the total wattage requirements and optimal generator size for your appliances
Add Your Appliances
Appliance #1
Power during normal operation
Power needed to start
Important Note
Only appliances with both rated and surge watts entered will be included in calculations. The generator wattage is based on total surge watts to ensure all appliances can start properly.
Common Appliance Wattages
Kitchen Appliances
HVAC & Electronics
* Values shown as Rated Watts / Surge Watts. Actual values may vary by model and manufacturer.
Generator Types
Portable Generator
1-10 kVA, gasoline/propane
Good for temporary power
Standby Generator
7-150 kVA, natural gas/propane
Automatic whole-house backup
Inverter Generator
1-7 kVA, ultra-quiet
Clean power for electronics
Generator Tips
Always use surge watts for sizing
Don't run at 100% capacity continuously
Consider starting appliances separately
Plan for future appliances
Check local electrical codes
Sizing Guide
Small Home
5-10 kVA
Essential appliances only
Medium Home
10-20 kVA
Most appliances + AC
Large Home
20+ kVA
Whole house coverage
How Generator Sizing Works
Understanding Power Requirements
Rated Watts (Running Watts)
The continuous power consumed during normal operation. This is what the appliance needs to keep running.
Surge Watts (Starting Watts)
The higher power needed when starting up. Motors and compressors typically require 2-3x their running watts to start.
Generator Wattage
Based on total surge watts to ensure all appliances can start. This is your minimum generator requirement.
Sizing Calculations
Step-by-Step Process
Step 1: Add up all rated watts for total running power
Step 2: Add up all surge watts for total starting power
Step 3: Calculate apparent power: Surge Watts ÷ Power Factor
Step 4: Account for operating capacity: Apparent Power ÷ Operating %
Example Calculation
For 3,500W surge power at 0.8 power factor and 70% capacity:
Required size = 3,500 ÷ 0.8 ÷ 0.7 = 6.25 kVA
Power Factor and Generator Efficiency
Power Factor
• Measures electrical efficiency (0-1)
• Standard generators: 0.8 (80%)
• Higher PF = more efficient
• Affects apparent power calculation
Operating Capacity
• Recommended: 70-80% max load
• Extends generator lifespan
• Reduces fuel consumption
• Provides safety margin
Apparent Power
• Total power generator must produce
• Measured in kVA (not kW)
• Accounts for inefficiencies
• Used for generator rating