To determine what size generator you need, you should consider the appliances and systems you want to power during an outage and add up their wattage. You will need to know both the running watts and starting watts of each device. Running watts refer to the continuous energy needed to keep your devices running, while starting watts refer to the extra watts needed for the first few seconds that it takes to power up motor-driven devices. Once you have the total running watts of all devices you want to run at the same time and your highest single starting watts, add them together to figure out what size generator would be right for you. According to the U.S. General Services Administration, generators should be sized to approximately 110% of design load, but should ideally run at a range of 50% to 80% of their rated capacity.
Its important to note that if an appliance has a motor, you will need to calculate the total wattage using a formula. Additionally, some appliances, such as air conditioners, refrigerators, and sump pumps, draw a lot more wattage at the moment they’re cycling on, which can throw off your calculations if you don’t account for surge watts.
Below is a list of approximate running wattage for various household appliances and technology:
- Refrigerator/Freezer: 600 - 800
- Electric Range (one element): 2500
- Toaster: 1100 - 1700
- Microwave: 1200
- Hot Plate: 1250
- Coffeemaker: 400 - 800
Remember that the more appliances you want to use, the bigger generator you will need.
