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Advanced electrical check

Breaker sizing calculator

Estimate a standard breaker size while keeping the load, continuous-duty margin, and conductor coordination visible.

No account Instant result Explanation included
1Tell us what you knowStart with the fields you already understand.
2See the recommendationSee the number and why Solar Plan Lab suggested it.
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Advanced safety check. Start with connected watts unless you know the circuit current from measurement or a data sheet. This result is a planning starting point, not a final protection schedule. Return to Full Designer →

Inputs

i
Most homeowners should use connected watts. Choose known current only when it comes from a measured value or equipment data sheet.
i
Voltage of the protected circuit. Example: 51.2 V nominal for a 48 V-class LiFePO4 battery circuit, or 230 V AC.
i
Total equipment power connected to the circuit. Example: 3000 W inverter load.
i
Used only when “I know the circuit current” is selected. Otherwise the calculator estimates current from connected watts and circuit voltage.
i
A continuous load runs for a long period. A larger design margin is usually required.
Visual aid

Protection device visual

SOLAR PLAN LAB
MCB / DC BREAKER
Breaker purpose

A breaker disconnects the circuit when current becomes unsafe. It must protect the cable and match the circuit voltage and fault-current requirements.

Example

Example calculation

Solar Plan Lab uses the current project values to show how the recommendation changes.

Common mistake

Do not rely on one number alone

Check the result against actual equipment and site conditions.

Frequently asked

Is this installation-ready?

No. It is a planning estimate that should be verified by qualified professionals.

How was this calculated?

Calculation method

Formula

The calculator uses the displayed inputs and standard planning relationships.

Important assumptions

Verify the final design against actual equipment data sheets, site conditions, and applicable requirements.

Read the full methodology and update history →
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