The Hidden Impact of Grid‐Connected Solar on HT Power Factor

As India accelerates its transition to renewable energy, grid-tied solar photovoltaic (PV) installations. The Understanding is simple: inject clean kilowatts (kW) into the load and grid, displace fossil generation, cut emissions. Yet beneath this success story lies an underappreciated electrical challenge—power factor (PF) erosion—threatening both industrial consumers and distribution utilities.

Understanding the PF Paradox

At its essence, power factor is the ratio of real power (kW)—the work-doing component—to apparent power (kVA), which combines real and reactive (kvar) currents. A PF of 1.0 means every ampere contributes to work; lower PFs imply wasted current and higher losses.

Grid-tied inverters deliver only real power. They inject kW into the network at near-unity PF (0.99), but they do not supply or absorb reactive current—the kvar that motors, transformers and lighting still demand.

When solar generation peaks, net kW imported from the grid plunges. But kvar import remains essentially unchanged, since your factory’s inductive loads continue drawing reactive current unabated. The result: kVA falls less than kW, and PF (kW/kVA) inevitably drops.

SO yes after shifting to solar, there is a change in your PF.

Why PF Matters if you’re an HT consumer (Large power consumers)

1. Regulatory Penalties: State utilities (DISCOMs) levy steep surcharges on consumers whose monthly PF falls below 0.90 or 0.95. Even a 0.10 PF dip can translate into lakh of rupees in penalties for HT consumers

2. Network Stability Poor PF increases line losses and voltage fluctuations, straining distribution transformers and hindering voltage regulation—particularly acute in weak rural networks where solar farms often interconnect.

3. Under-Recovered Costs DISCOMs recover transmission and distribution costs through kVAH billing. Widespread PF slippage shifts costs onto utility balance sheets, weakening financial health and impeding further renewable rollout.

The Main Culprits of Solar-Induced PF Drop

1. Solar Only Offsets Real Power:

   1. PV inverters default to unity PF export—no kvar compensation.

   2. Daytime kW imports shrink; kvar imports (e.g., magnetizing currents, inductive motors) stay flat.

2. Capacitor Bank Mismatch:

   1. Capacitor banks sized for full load will over-compensate under reduced kW, possibly causing leading PF excursions.

   2. Premature removal of caps (assuming solar will “fix” PF) leads to under-compensation when clouds return.

3. Net-Import Metering:

   1. Import-only PF meters ignore export kvar—if your PV exports kW, the meter still logs kvar import, collapsing the net PF reading.

4. Inverter PF Settings:

   1. Barely any inverter manufactures/suppliers in India are configured for reactive support. Some modern designs can target a fixed PF (e.g., 0.95 lag/lead) or follow a VAr-droop curve—yet these modes are often disabled by default.

5. Load Profile Shift:

   1. Solar flattens daytime kW peaks more than kvar peaks. Since PF penalties often reference “75 % of highest demand” over 11 months, the kvar share in that demand block rises, pulling down the blended PF.

6. Auto PF Correction (APFC) Panels

   Deploy detuned capacitor banks with PF relays at the incomer. Size the banks based on post-solar kvar profiles—typically 80–200 kVAr, but it will need to be upgraded after installing solar

7. Enable Inverter VAr Support (Future)

   Once technology evolves, configure PV inverters for dynamic VAr injection/absorption. Coordinate with DISCOM metering to ensure bi-directional PF measurement.

8. Hybrid Approaches Combine modest capacitor banks with selective inverter upgrades or STATCOM modules for fast, resonance-free correction.

Why Batteries Alone Aren’t Ideal for PF Correction

Economic mismatch:

• BESS are capitalized for active-energy shifts (kWh), not kvar delivery—dedicated capacitor banks or STATCOMs deliver reactive support at a much lower ₹/kvar cost.

Lifecycle impact:

• Cycling batteries purely for reactive power wears on their state-of-health without providing useful energy discharge, reducing lifespan.

Complex controls & metering:

• Battery inverters require advanced firmware and bi-directional, PF-aware meters; standard APFC panels work on simple PF thresholds and offer proven reliability.

Leverage Battery Energy Storage (BESS) with VAr Capability (if already deployed)

If you’re using batteries for load-shifting or backup, choose inverters that support reactive-power modes.

During high solar export, they can inject leading kvar; during inductive load peaks, they can absorb excess kvar - provided PF-aware metering and careful commissioning.