GENERATOR WATTAGE CALCULATOR
If you want a generator for home standby, for example, if you want to run your refrigerator, you’ll need at least 2500 watts or more. And if you want to use a transfer switch so that power can go directly into your home, you’ll want a generator with at least 3000 watts.
You’ll also need to consider the maximum and rated power of the generator. This is important depending on what items you want to run off of your generator. Items such as toaster, lamps, and coffee makers are resistive, or constant loads and their total load can be calculated at amps x 1. Items such as saws and drills are reactive loads and while the running load may be small, the starting load should be calculated at running amps x 3. Remember, after the intial start less power is required for actual operation.
Always remember that simple power management will allow a smaller generator to do a big job. Very seldom are all tools or appliances operating simultaneously. When calculating power requirements, consider the starting requirements are only for the initial start and then additional tools may be operated in addition.
If your home has a deep well pump with up to 1 HP motor, a 5000 watt generator will be required to provide the starting capacity for the pump. Larger wattage units can be selected for simultaneous starting ands operation of multiple appliances
Remember Ohm’s Law from High School Physics?
Watts = Volts x Amps
Amps = Watts/Volts
So if you have two of the numbers (e.g. volts, amps) then you can find out the other (e.g. watts). This can help you to determine the rated power that you’ll need from your generator.