Always use starting watts, not running watts, when determining the correct electrical load requirements. Keep in mind that if you coordinate your power usage wisely you do not have to operate everything all at once. Therefore, for emergency use you don t necessarily need to size the generator to operate everything simultaneously. This will allow room for future growth. For example, if you determine that you will need a 15 kW generator then it is advisable to purchase an 18 kW generator to accommodate future expansion.
Electrical motors present special electrical startup considerations.
They can require up to four times their rated running wattage to start. Motor nameplates generally will show starting watts, some as high as nine times the running wattage. Check the nameplate to be sure. Be certain to use the starting watts when figuring the correct electrical load requirements. Motors of higher HP are not generally used.