HS-T06Standalone tool

Generator sizing calculator

Screen continuous and starting-watt capacity from the loads you plan to run, the largest startup surge, and visible headroom.

HS TOOL / 06

Screen generator capacity.

Add continuous loads, the largest extra startup surge, and visible headroom without pretending to design a transfer system.

COMMON WAYS TO ASK

What size generator do I need?
Add running and starting watts
Estimate generator headroom

QUICK ANSWER

What this calculator tells you.

Add the simultaneous running loads, identify the largest motor startup surge, and preserve headroom. The result is an initial capacity screen, not permission to connect a generator to building wiring.

WORKED EXAMPLE

Keep essential loads running

INPUTFridge + lights + router · largest startup surge

RESULTContinuous load plus surge and explicit headroom

CHECK THE EDGE CASES

Questions people ask next.

Why are starting watts higher than running watts?

Motors and compressors can draw a short surge while starting. A generator must tolerate that surge while supporting the other loads already running.

Can I connect a portable generator to a wall outlet?

No. Backfeeding can energize utility lines and endanger people. Building connections require approved transfer equipment and qualified installation; operate combustion generators outdoors per manufacturer guidance.