Home Solar Battery Backup Sizing Calculator
Choosing the right generator size means balancing the running wattage of your appliances with their startup surge. Enter your key appliance loads below to get a recommended generator size.
About this calculator
Determine the right generator wattage for your home by totaling the power draw of essential appliances you want to keep running during an outage.
Frequently Asked Questions
Why do I need to account for surge watts separately?
Many appliances, especially those with motors like refrigerators or well pumps, require a short burst of extra power to start up, which can be 2-3x their running wattage.
How much safety margin should I use?
A 20% margin is typical to account for voltage fluctuations and ensure you don't overload the generator during startup surges.
Can I run multiple appliances that all need surge power at once?
You should size for the single highest surge appliance since it's rare for multiple large motors to start simultaneously, but stagger starting them to be safe.