Choose the appliances you want to run during an outage. We’ll estimate your power demand, include startup surge and a capacity buffer, then suggest generator models to compare.
Choose a preset, then adjust quantities and running watts. Use your appliance nameplate or manual whenever possible.
For air conditioners, pumps and other motors, look for starting watts, locked-rotor amps (LRA), or manufacturer generator-sizing guidance.
Submit your appliance selections to see your estimated generator size and matching generator recommendations.
The calculator adds the running watts of selected appliances, applies your surge allowance, adds a capacity buffer, and rounds up to the next 500 watts. Startup loads can overlap and vary, so this is a shopping guide—not an electrical engineering calculation.
Choosing the right generator size is one of the most important steps when preparing your home for a power outage. A generator that is too small may not provide enough electricity to operate essential appliances, while an oversized generator can cost significantly more than necessary.
Our free home generator sizing calculator helps estimate how many watts you need based on the appliances and equipment you want to operate. Simply select your refrigerator, freezer, heating and cooling equipment, lighting, electronics, and other household appliances to receive an estimated generator capacity.
A generator sizing calculator estimates your electrical requirements by adding the running wattage of the appliances you select. It then applies additional allowances for startup demand and reserve capacity to provide an initial generator size recommendation.
Some appliances, particularly those with electric motors and compressors, require additional power when starting. Refrigerators, air conditioners, well pumps, and sump pumps are examples of equipment that may have higher starting wattage than running wattage.
For the most accurate generator sizing, check the manufacturer's specifications or appliance nameplate for actual running and starting requirements.
The generator size you need depends on which appliances you plan to operate simultaneously. A smaller generator may be sufficient for essential household equipment, while a larger generator may be necessary for central air conditioning, electric water heaters, electric ranges, and other high-demand appliances.
These are general capacity ranges, not guarantees of appliance compatibility. Actual requirements depend on appliance starting loads, generator rated output, fuel type, and which equipment operates at the same time.
Running watts represent the electricity an appliance needs to continue operating. Starting watts represent the additional power some appliances require when their motors or compressors initially start.
When selecting a generator, it is important to consider both values. A generator may have enough running wattage for your appliances but still struggle to start equipment with high initial power demands.
Portable generators are generally less expensive and can provide backup electricity for selected appliances using properly rated extension cords or an approved transfer system.
Standby generators are permanently installed systems that can automatically supply backup electricity to designated household circuits or, when properly sized, a larger portion of the home.
Whole-home generator installations require appropriate electrical equipment and professional assessment. Always use a qualified electrician for transfer switch and household wiring connections.
Many household refrigerators use several hundred watts while running, but starting requirements can be substantially higher. Check the manufacturer's specifications for your particular refrigerator.
A 5,000-watt generator can power selected essential household appliances, but it generally cannot operate every appliance in a typical home simultaneously. Large loads such as central air conditioning and electric ranges may exceed its capacity.
Central air conditioning requirements vary significantly based on system size, efficiency, compressor technology, and starting current. Check the HVAC equipment nameplate and consult a qualified electrician or generator installer.
Not necessarily. A properly sized generator should meet your expected electrical demand without requiring unnecessary additional capacity. Fuel consumption, purchase price, and maintenance should also be considered.
No. Never connect a portable generator directly to household wiring using an improvised connection. A properly installed transfer switch or approved interlock system is required to prevent dangerous backfeeding.