ATS Sizing Tool
From service amps or generator kW to the next standard transfer-switch frame, using the 125% continuous rule.
Recommended ATS frame
200A
120 A load × 1.25 = 150 A
30407080100150200225260400600800100012001600200030004000
Standard frames from the same ladder our sizing engine uses. Withstand/close-on ratings, poles and transition type are an engineering call. Verify with a licensed electrician.
Generator size · 80 kW
kW
Voltage
Phase
Sizing from the generator suits essential-loads transfer downstream. For whole-building transfer at the service entrance, switch the basis above to By Service Size.
Read the ATS guideThis tool is a planning aid. It does not replace final engineering review, AHJ determination, or a formal quote. Verify requirements with your AHJ and a licensed engineer.
New to transfer switches? the ATS guide