Inverter Sizing Calculator
Size your inverter from real AC loads, surge factors, and simultaneity. See required W/VA, worst-case DC current @ system V, and suggested cable & fuse.
Why do I need both W and VA?
Inverters are limited by **W** (real power) and **VA** (apparent power). Poor power factor inflates VA. We convert your W using the **minimum PF** so the inverter isn’t overloaded on VA.
How do I pick simultaneity?
Use **1.0** for things that always run together; **0.5** for sometimes overlapping; **0.1–0.3** for rare overlap. This keeps the continuous requirement realistic without under-sizing surge.
What headroom should I add to the inverter size?
Commonly **15–30%** above calculated continuous watts. If you have high-surge appliances (compressors, grinders), keep extra margin and ensure the inverter’s **surge spec** meets the calculated worst case.
How do I choose the DC fuse and cables?
Fuse to protect the **smallest conductor** and withstand **peak DC amps**: start with **~125% of peak** then round to a standard size that does **not** exceed cable ampacity. Select cable by ampacity and confirm voltage drop (≲3–5% on short DC runs).
My result is close to limits—what should I adjust first?
Increase **system voltage** (e.g., 24 V halves DC current), choose a **higher inverter class**, or **thicken cables**. All three reduce stress and heat; voltage change yields the biggest current reduction.