This is known as coil whine and is perfectly normal in modern inverters, especially when the system is working hard (charging, discharging, or exporting to the grid). It happens when electronic components like coils or transformers vibrate slightly as electricity flows through them at high frequencies.
It’s not a fault and doesn’t affect performance or safety — just a harmless byproduct of efficient power conversion. In quiet environments, it can be more noticeable, but rest assured it’s common in many types of electrical equipment.
Why Does It Happen?
- Magnetic Vibration
Inverters use switching components (like MOSFETs or IGBTs) that rapidly turn power on and off — often at frequencies from 4 kHz to 20+ kHz.- These signals pass through inductors and transformers.
- The magnetic fields inside these components expand and collapse rapidly, causing mechanical vibration of the core, windings, or surrounding parts.
- Resonance
- When these vibrations match a natural resonance frequency of the component or PCB, they can amplify, making the noise louder and more noticeable.
- Load-Dependent Behavior
- Under higher loads (like peak charging, discharging, or grid export), current flow increases, and switching dynamics change — making coil whine more likely or more audible.
- You’ll often hear this during battery charge/discharge, grid-feed, or high PV production.
Is It Normal?
Yes — this is typically normal for inverters and other power electronics, especially:
- When pushed harder under higher loads.
- If switching frequencies fall in the 7–14 kHz range (audible to most people).
- In quiet environments where even faint noise is noticeable.
It’s not a sign of a fault, provided:
- There are no other symptoms (like heat, failure, error codes).
- The noise isn’t suddenly louder than usual or accompanied by crackling or irregular sounds.
Why It’s More Noticeable Sometimes:
- Human ears are very sensitive between 8–12 kHz — we evolved that way to detect subtle threats.
- If the inverter is mounted to a wall that resonates (e.g., plasterboard or wood), it can amplify the vibration like a speaker.
- Some people are more sensitive than others — especially younger users or those with no hearing loss.
