Why It Matters — Even Below 30kW
It’s Not Just About Kilowatts
When selecting hybrid inverters for small commercial or residential projects, most buyers focus on:
- Output power (kW)
- Battery compatibility
- AC/DC coupling
- MPPT efficiency
But one crucial spec often gets overlooked — reactive power support, also called VAR (volt-ampere reactive) control.
In grid-connected systems, reactive power capability is essential for maintaining voltage stability, grid code compliance, and even local inverter permit approvals.
1. What Is Reactive Power?
In simple terms:
- Active power (kW) = what actually powers your appliances
- Reactive power (kVAR) = energy used to maintain voltage and magnetic fields
Reactive power doesn’t do work like lighting a bulb, but without it, voltage collapses, and power delivery becomes unstable — especially on weak or rural grids.
Inverters that support reactive power can absorb or supply VARs to help the grid maintain voltage stability.
2. Why It Matters for Small-Scale Projects
🔌 Grid-Tied Installations
Most grid operators today require even small-scale inverters to provide some reactive power control, especially:
- In urban areas with high solar penetration
- On weak or long feeders where voltage fluctuates
- In countries with modern interconnection rules (e.g., Europe, Australia, South Africa)
📉 Poor Reactive Support = Grid Rejection
If an inverter can’t comply with local grid support protocols, it may:
- Get rejected for interconnection
- Cause nuisance trips or instability
- Lead to underperformance penalties in C&I PPAs
3. What Does Reactive Power Support Look Like in Inverters?
Modern hybrid inverters often support reactive control through:
| Feature | Description |
|---|---|
| Power Factor Adjustment | Ability to operate at PF < 1 (e.g. 0.9 lag/lead) |
| Q(U) or Volt-VAR Curve | Supply or absorb VARs based on voltage changes |
| Remote Reactive Power Control | Using communication protocols like Modbus or Sunspec |
| Dynamic VAR Support | Fast response to grid events or voltage sag |
Note: Even a 5kW inverter can play a small role in supporting local voltage, especially when grouped in a residential feeder.
4. What to Ask When Sourcing
When comparing small-scale hybrid inverters (5–30kW), look beyond headline specs.
Key questions:
- ✅ Does it support configurable power factor settings?
- ✅ Can it follow utility Volt-VAR or Watt-VAR curves?
- ✅ Is reactive power available in both grid-tied and islanded modes?
- ✅ Is control manual, automatic, or remote via EMS?
- ✅ Are reactive functions certified (e.g., VDE 4105, IEEE 1547, SA Grid Code)?
5. Common Use Cases
🏠 Residential Clusters (5–10kW)
When many homes export PV power at the same time, grid voltage can spike. Reactive absorption (lagging VARs) helps reduce voltage and prevent disconnection.
🏢 Small Commercial Rooftops (10–30kW)
Inverters must support PF control to meet utility interconnection rules. Some utilities even require VAR provisioning during non-generation hours.
🌍 Remote Grids or Microgrids
Hybrid inverters in isolated systems must manage both active and reactive power flows to maintain grid stability.
6. Challenges in Reactive Power Deployment
- Misunderstanding the function — Some buyers think reactive control is only for large-scale systems
- Limited configurability — Not all low-cost inverters support advanced PF or Volt-VAR features
- Installer knowledge gap — Even good installers may not set reactive settings properly
- Compliance gaps — Some regions now enforce reactive support testing during commissioning
7. Recommendations for System Buyers and Exporters
✅ For Installers/Buyers:
- Ask your inverter supplier to confirm VAR control capability
- Preconfigure PF settings before commissioning
- Work with local utility on interconnection expectations
✅ For Exporters/Brands:
- Include Volt-VAR control guides in manuals
- Provide default country-based settings
- Train partners on power quality impact of reactive settings
Remember: VAR control isn’t a “big project” feature anymore. It’s standard on modern hybrid systems — and your customer may need it.
A Small Feature With Big Grid Impact
As solar+storage spreads beyond homes into small businesses, farms, and schools, the role of reactive power grows.
Hybrid inverters that support configurable, automated VAR functions can:
- Prevent unwanted voltage trips
- Ensure interconnection approval
- Enhance local grid stability
If you’re buying or selling sub-30kW systems, make sure reactive power support is on your checklist — not just kW and battery specs.
