Generator Calculators: Free Tools for Sizing & Load Matching
Size your backup or primary generator accurately with our free online generator calculators. Whether you need emergency power for a residential home, a construction site, or a critical commercial facility, these tools calculate total electrical load, required generator capacity, and fuel consumption instantly. Enter your appliance wattages, motor starting requirements, and load diversity factor to determine the minimum kW or kVA rating that handles peak demand without overload. Each calculator includes starting surge multipliers for refrigerators, air conditioners, and well pumps, plus power factor adjustments for accurate kVA sizing. Avoid costly mistakes from undersized units that trip on startup or oversized generators that waste fuel and money. Electricians, contractors, and homeowners use these tools to match generator output to real-world load profiles. No signup required—access from any device and get NEC-aligned sizing recommendations in minutes.
