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Inverter Size Calculator

Inverter rating for a solar array or off-grid load, including surge headroom.

Enter values

Results update as you type.

Result

Inverter size

5 kW

Calculated requirement
5,000 W
Surge capacity needed
10,000 W
Current at 230 V
21.74 A
DC current at 48 V
109.6 A
Suggested DC breaker
113 A

About the Inverter Size Calculator

Inverter rating for a solar array or off-grid load, including surge headroom.

Also known as: what size inverter do i need, inverter sizing calculator, solar inverter kw, off grid inverter.

How to use this calculator

  1. Enter size for, growth headroom and the other fields.
  2. The result updates instantly as you type — press Calculate (or Enter) at any time.
  3. Review the breakdown shown under the main result.
  4. Use Copy result or Share to save the answer or send a link with your inputs.

Formula

inverter W = array Wp ÷ DC:AC ratio × (1 + headroom)

Worked example

Using the values pre-filled in the calculator above:

  • Size for: A solar array
  • Array size = 5 kWp
  • DC to AC ratio = 1.2
  • Growth headroom = 20 %

the calculator returns:

  • Inverter size: 5 kW
  • Calculated requirement: 5,000 W
  • Surge capacity needed: 10,000 W
  • Current at 230 V: 21.74 A