Inverter Size Calculator
Use this inverter sizing workflow for early backup and off-grid planning. It does not choose a listed inverter or approve wiring, protection, transfer equipment, or interconnection.
- Minimum continuous rating
- W
- Minimum surge rating
- W
- Estimated apparent power
- VA
- Estimated DC input
- W
Calculation details
- Margin multiplier
- x
- Calculation basis
- Selection boundary
Recent results
Formulas
- Margin multiplier = 1 + margin percent / 100
- Continuous rating watts = running watts x margin multiplier
- Surge rating watts = surge watts x margin multiplier
- Apparent power VA = continuous rating watts / power factor
- Estimated DC input watts = continuous rating watts / efficiency factor
Use this calculator
Estimate inverter continuous watts, surge watts, VA, and DC input watts from entered load assumptions.
Read the result
Review the calculated values with their displayed units and assumptions. The result is a planning aid for the stated inputs, not a final equipment or installation decision.
Check before final work
This inverter size estimate uses entered load assumptions only. It does not approve waveform, surge duration, battery current, protection, transfer equipment, utility interconnection, or code compliance.
FAQs
Does this choose an inverter model?
No. It estimates continuous and surge ratings from entered assumptions. Check manufacturer ratings and project requirements separately.
Why is power factor included?
Power factor converts the continuous watt estimate into an apparent-power VA estimate for loads where VA matters.