Inverter Sizing Calculator
Pick the right inverter wattage for your AC loads.
About
Inverter rating must exceed the sum of simultaneous AC loads (continuous), and its peak surge rating must handle the largest startup spike (refrigerator compressor, power tool, well pump).
How it works
- Sum the watts of every AC device that may run at once.
- Identify the single biggest surge (often a fridge or AC compressor at startup).
- Apply 25% safety margin to continuous; surge is taken as the spec value.
Frequently asked questions
What size inverter do I need for a fridge?+
A typical full-size fridge uses 100–150 W continuous and surges to 600–1,200 W at compressor start. A 1,500 W continuous / 3,000 W surge inverter handles it comfortably.
Why does the inverter trip when I start my power tool?+
Power tools and motors draw 3–5× their rated wattage at startup. Your inverter's surge rating must cover that spike, even if continuous demand is far lower. A 2,000 W tool can spike to 8,000 W for 100 ms.
Pure sine vs modified sine wave?+
Pure sine for any modern electronics, motors, medical devices and inductive loads. Modified sine is only acceptable for resistive heating and incandescent lights. The price gap has shrunk — buy pure sine.
How does inverter size affect efficiency?+
Most inverters peak at 30–60% load. Running a 5 kW inverter at 100 W is wasteful (idle losses dominate). Running it at 4 kW is at the upper end of the efficiency curve. Right-size, don't over-size.