Starting Watts vs. Running Watts
The power that keeps an appliance running is different from the extra burst it needs to turn on.
Running watts keep things going
Running watts are the power your generator can keep supplying. Starting watts are a bigger amount it can supply for a short time. A generator advertised as 13,000 watts might provide only 10,500 running watts on gasoline. Use the running number when you add up appliances you want to keep on.
Starting watts help appliances turn on
A refrigerator or pump needs a quick burst of extra power to get its motor moving. Lights and heaters usually do not need the same kind of burst. Check the starting requirement in the appliance manual or ask its manufacturer. Two generators with the same starting-watt number may still handle a particular motor differently.
Turning things on separately can help
You may be able to start one appliance, wait for it to settle, and then turn on the next. That can reduce the power needed all at once. But refrigerators, freezers, and automatic pumps can switch themselves back on. If you cannot control when they restart, allow enough power for them to turn on together.
Check more than the wattage
The appliance voltage must match the generator. Each outlet, cord, and circuit breaker also limits how much you can plug into it. A large plug marked 50A does not mean the generator can supply that much power all the time. Ask an electrician to check larger appliances and home connections.