Inverter Sizing Guide 🔌
How to Use the Inverter Sizing Guide
Enter total load wattage and simultaneous usage rate. For motor loads (refrigerators, AC, pumps), enter the largest motor load — these require 3-7x surge current at startup.
The recommended VA rating is based on the higher of continuous power need and surge power. Add 20-25% headroom to the calculated value for safety.
Use pure sine wave inverters for sensitive electronics (computers, medical devices, audio equipment). Modified sine wave inverters work for simple resistive loads like heaters and incandescent lights.
FAQ
What is the difference between pure sine wave and modified sine wave inverters?
Pure sine wave inverters produce clean AC power identical to grid power, safe for all electronics. Modified sine wave inverters are cheaper but can damage sensitive electronics, motors, and medical equipment. Always use pure sine wave for computers, TVs, and appliances with variable speed motors.
Why do motors need surge power at startup?
Electric motors (refrigerators, pumps, AC units) draw 3–7× their running wattage for 1–3 seconds at startup. A 500W refrigerator may need 2,000–3,500W surge capacity. Your inverter must handle this peak without shutting down.
How much headroom should I add to my inverter size?
Add 20–25% headroom above your calculated peak load. If your calculation shows 2,000W needed, choose a 2,500W inverter. This prevents overheating and extends inverter lifespan.
Can I run an air conditioner on an off-grid inverter?
Yes, but AC units are power-hungry. A 1-ton (12,000 BTU) AC draws about 1,200W running and 3,600W+ at startup. You'll need a 3,000–4,000W inverter and a large battery bank to run AC off-grid.
What is inverter efficiency and how does it affect my system?
Inverter efficiency (typically 90–95%) means some power is lost as heat during conversion. A 95% efficient inverter wastes 5% of battery power. Factor this into your daily consumption calculations.