Load Calculator
Choose what you want to run. Find the inverter size, battery quantity and Ah capacity for your backup time.
How the estimate works
Results assume every selected appliance runs for the full backup period using 12V lead-acid inverter batteries. Battery capacity allows for 85% inverter efficiency and 50% usable battery capacity. Inverter sizing allows 25% running-load headroom and a power factor of 0.8.
Calculation and battery connection details
Running load = watts × quantity. Starting estimate adds the largest single motor's extra starting load (2× for fans, 3× for listed pumps/compressors). Inverter VA = the larger of running watts × 1.25 / 0.8 or estimated starting watts / 0.8, rounded up to a suggested size.
Ah per battery = running watts × backup hours / (bank volts × 0.85 × 0.50). Capacity rounds up to an example size between 80 and 300Ah. Auto mode suggests a 12/24/48/96V bank based on load and required capacity; exact inverter voltage and available battery sizes vary by manufacturer. Series connection increases voltage while Ah stays the same. All batteries must have matching capacity, type and age.
Motor start-up demand, battery age, temperature and discharge rate affect real performance. Appliances starting together can need more surge power. Check the inverter's continuous watt rating, surge duration, DC voltage and charging compatibility with your dealer. This is a sizing estimate, not a guaranteed backup duration.