By choosing breakers, not by hoping the interlock will shed load for you. An interlock only prevents the generator and the utility from being tied together. Once the generator breaker is on, every branch breaker you close is a load. The portable-versus-standby page and the r/Generator advice are consistent: people who like interlocks for flexibility also have to manage overloads themselves. Size a running and starting budget with the calculator, write down which circuits are in that budget, and default the dryer, range, electric water heater, and EV charger to off.
A practical sequence:
- Put the generator outdoors, with the exhaust away from openings, and plug it into the inlet — never a dryer outlet.
- Turn the main off, slide the interlock, start the generator, then close the generator breaker.
- Bring on the fridge, furnace or boiler controls, a few lights, and communications first. Wait before starting a well or a sump, and start motors one at a time.
- If the generator bogs, the lights dim badly, or an overload light comes on, turn loads off; do not keep resetting.
The Honda-based fridge + 1/3 hp furnace fan + lights example is only about 1,292 running watts and 2,300 starting watts. Honda’s electric dryer alone is 5,400 W running. Knowing those two facts keeps a lot of interlock overloads from happening. A 30-amp inlet is 7,200 W at 240 V; a 50-amp inlet is 12,000 W — circuit limits, not a promise the generator can produce that much.
This is not a permit calculation, a utility approval, or a substitute for a licensed electrician, HVAC contractor, or the authority having jurisdiction. Panel Headroom is an independent educational site. It is not a utility, a certification body, or a contractor. Electrical and generator work that is done incorrectly can cause fire, shock, or carbon monoxide poisoning. Use the adopted electrical code and manufacturer instructions; pull permits where required.