On Grid Inverter

ALMM and inverter compliance: MNRE’s current ALMM page publishes solar PV module and cell lists, not an inverter list. Verify the inverter’s exact model documents and applicable scheme or DISCOM requirements separately.

What is an on grid inverter

An on grid inverter is a solar inverter that converts the DC produced by PV modules into AC and pushes that AC directly into the utility distribution network. It is also called a grid-tie inverter, grid-connected inverter or grid-interactive inverter. The defining feature is dependence: without grid voltage and frequency present at the output terminals, the inverter does not produce power.

On the grid side it behaves as a controlled current source. The grid sets the voltage and frequency. The inverter pushes a current waveform locked in phase with that voltage, with very low harmonic distortion. On the DC side it acts as a maximum power point tracker, holding the array at the voltage that yields the most watts at that instant.

There is no battery, no transfer switch, and no standby mode. When the grid disappears, the inverter must disconnect within milliseconds. This is the most important safety property of a grid-tie inverter, and it is the reason on-grid systems do not provide backup during outages.

In India, on grid inverters dominate the rooftop solar market. The MNRE PM Surya Ghar Muft Bijli Yojana, almost all C&I projects, and the bulk of state subsidy programs are designed around grid-connected, net-metered systems using on grid inverters.

On grid inverter explained simply

Think of your house wiring as a river. The utility grid keeps the river flowing at a steady level. A solar panel produces DC, which is the wrong kind of water for this river. An on grid inverter is the pump that takes panel DC and pushes AC into the river at exactly the same rhythm as the existing flow.

If your home is using less than the panels are making, the extra water flows upstream into the neighbour’s pipes. Your meter spins backwards, and the DISCOM credits you. If the river dries up because the grid is off, the pump shuts off too. You get no backup. That is the deal.

For most Indian homes with a reliable enough grid, this is the cheapest and simplest way to use solar. You do not pay for batteries, you do not lose energy in storage cycles, and you cut your bill by 70 to 95 percent depending on roof size and consumption pattern.

Why on grid inverters matter

Cost. On grid systems are roughly 35 to 50 percent cheaper than equivalent hybrid systems because batteries are skipped entirely. A typical 5 kW rooftop in India costs ₹2.5 to ₹3.5 lakh on-grid, against ₹4.5 to ₹6.5 lakh with storage.

Efficiency. There is no round-trip loss in a battery. Every kWh of solar generated either powers the load directly or goes to the grid at near-unity efficiency. Hybrid systems typically lose 10 to 15 percent in charge and discharge cycles.

Grid stability. Modern on grid inverters perform reactive power support, voltage ride-through and frequency response. As rooftop solar penetration climbs in states like Gujarat, Kerala and Tamil Nadu, these inverter functions help the grid absorb variable solar without instability.

How an on grid inverter works

The path from sunlight to grid current follows five stages.

1. DC collection. PV strings feed the inverter through fused combiner boxes. Each MPPT input has its own voltage and current sensor.
2. MPPT control. The processor sweeps the array voltage to find the knee of the I-V curve, then holds the operating point there. Most algorithms use perturb-and-observe or incremental conductance, refreshed every few milliseconds.
3. DC boost or buck. A boost converter raises array voltage to the DC bus level needed for inversion, typically 380 to 800 V depending on AC side.
4. Inversion. IGBT or SiC switches chop the DC bus at 16 to 50 kHz using pulse-width modulation. An LCL filter smooths the chopped output into a clean sine wave.
5. Grid synchronisation and export. A phase-locked loop matches the inverter output to grid voltage and frequency. Anti-islanding logic continuously checks that the grid is alive. If grid voltage, frequency or impedance moves outside the configured window, the AC contactor opens.

All of this happens with a control loop running at the millisecond scale. Modern inverters also report telemetry over Modbus or SunSpec, push it to the cloud over WiFi or 4G, and accept remote firmware updates.

Technical deep dive

Conversion efficiency

European efficiency is the weighted measure most installers quote. It assumes the inverter spends most of its time at part-load. The formula weights efficiency at 5, 10, 20, 30, 50 and 100 percent loading:

A good Indian rooftop inverter posts ηEU between 97.0 and 98.0 percent. Peak efficiency at 50 percent load can touch 98.6 percent on SiC platforms.

MPPT window

The DC voltage window where MPPT works defines what string configurations are legal. For a 5 kW single-phase inverter, a typical MPPT window is 100 to 500 V with a startup voltage near 100 V. The string voltage at the coldest expected ambient must stay below the absolute maximum DC input, and at the hottest noon must stay above the lower MPPT bound.

Grid code compliance

The Indian CEA grid code and IEEE 1547 require the inverter to ride through specific voltage and frequency excursions before tripping. Typical settings:

• Voltage trip: 0.85 to 1.10 pu, with low-voltage ride-through to 0.50 pu for 150 ms.
• Frequency trip: 47.5 to 51.5 Hz, with frequency-watt droop from 50.2 Hz.
• THD: less than 3 percent total, less than 4 percent on any individual harmonic up to the 50th.
• Power factor: adjustable from 0.8 leading to 0.8 lagging.

Topologies

Real-world applications

Residential solar. Single-phase 1 to 10 kW on grid inverters dominate Indian rooftop projects. Net metering credits surplus and offsets daytime consumption. Typical payback in India: 4 to 6 years.

Commercial solar. Three-phase 10 to 100 kW inverters power offices, schools, hospitals and small factories. Net or gross metering with state-specific tariffs. Payback in India is 3 to 5 years for daytime-heavy loads.

Industrial solar. 50 to 500 kW three-phase inverters connect to LT or HT panels through transformers, often delivered under a turnkey solar EPC contract. Reactive power support is often contractually required by the DISCOM.

Utility-scale solar. 1 to 5 MW central or large string inverters feed step-up transformers at 33 to 66 kV. These plants supply power under PPA contracts at fixed tariffs.

PM Surya Ghar projects. Subsidised 1 to 10 kW residential systems under the central scheme almost always use on grid inverters, paired with a single-phase or three-phase bidirectional meter.

Advantages of an on grid inverter

The cost per installed kW is the lowest among all solar inverter categories. Lifecycle energy yield is the highest because there are no battery losses. Footprint is small, since no battery cabinet is needed. Operation and maintenance are minimal, mostly dust cleaning, fan replacement and annual insulation resistance checks. Subsidy and tax-incentive eligibility is the broadest, because Indian schemes assume grid-tied operation.

Limitations

No backup during grid outages. In areas with poor supply, the inverter sits idle during the hours when you most need power. Export limits in some states cap the financial benefit. Reactive power and voltage rise can constrain how much solar a feeder can absorb in semi-urban areas. The inverter is a single point of failure for the AC string. Cybersecurity exposure is real, since most units talk to a vendor cloud over the internet.

Common problems

Frequent grid trips. The most common complaint in Indian installations. Usually root-caused to high midday grid voltage, low neutral conductor quality or undersized service cable. Fix by adjusting trip windows within CEA limits, upgrading the neutral, or moving the connection point closer to the transformer.

DC arc faults. Caused by loose MC4 connectors and water ingress. Annual torque checks prevent most of these.

Insulation resistance faults. PV cabling damp from monsoon water ingress trips Riso protection. The inverter refuses to start until panels dry out. Fix the cable gland, not the inverter.

Display errors like F30, E13, ISO error. Codes are vendor-specific. Always consult the manual before resetting more than twice.

Communication dropouts. WiFi credentials change, cellular SIMs expire, RS485 cables get vibration-damaged. Plan for periodic reconnection.

Best practices for on grid inverters

Mount in a shaded, ventilated location. Avoid west walls and metal sheds, which push internal temperature above derating thresholds. Use the manufacturer’s bracket and the recommended air clearance.

Size the AC cable for 1.5 percent voltage drop or less from the inverter to the meter. Long cable runs above 30 m are a frequent cause of trip-on-export.

Earth the inverter chassis and the PV array frame separately, then bond at the main earth bar. Use a Class II SPD on both DC and AC sides for Indian conditions.

Set up monitoring on day one. Without telemetry, low-yield faults can go unnoticed for months.

Schedule a 6-monthly check of DC connectors, fan filters and AC torque. Replace fans at 5 to 7 years even if they still spin.

Comparison: on grid vs other inverter types

For a full decision framework across all three architectures, see On-Grid vs Hybrid Inverter, Which Should You Actually Buy? and the off grid inverter glossary entry.

Indian market context

State DISCOMs enforce CEA grid standards through commissioning tests. The standard tests include anti-islanding within 2 seconds of grid loss, THD under 3 percent at rated output and 50 Hz frequency lock-in within ±0.5 Hz.

Net metering rules differ by state. Maharashtra and Gujarat allow net metering up to the sanctioned load. Karnataka and Tamil Nadu have moved towards gross metering for larger systems. Delhi and Kerala allow virtual net metering for group housing.

Standards and certifications

Common mistakes

Buying an inverter that is too small to save a few rupees. A 4 kW inverter on a 5 kW array sees clipping every clear day from 10 am to 2 pm.

Mounting the inverter on a west wall or inside an unventilated cupboard. Both push internal temperatures above derating limits.

Ignoring the AC isolator. A dedicated AC isolator next to the inverter is mandatory under CEA rules and required by every Indian DISCOM during commissioning.

Wiring strings to the wrong MPPT input pair. The inverter will run but each MPPT will average two mismatched strings, costing 4 to 8 percent annual yield.

Skipping surge protection. Indian thunderstorm zones see lightning surges that fry inverters not protected by Class II SPDs on both DC and AC.

Forgetting to commission the cloud monitoring. Without it, the first sign of trouble is a lower-than-expected bill three months later.

Letting the warranty card sit in a drawer. Registering the inverter on the manufacturer portal within 30 days is usually mandatory for extended warranty.

Mixing inverter brands on the same site. Different anti-islanding algorithms can interact badly, causing nuisance trips.

Further reading

For how On Grid Inverter plays out in real projects, these guides go deeper:

• On-Grid vs Hybrid vs Off-Grid: Decision Guide
• Best 3kW Solar Inverter in India 2026
• How Does a Solar Inverter Work? 2026 Guide
• Best On-Grid Solar Inverter 2026, Top Picks

Sources

• IEC 62109-1, -2, Safety of power converters for use in photovoltaic power systems, International Electrotechnical Commission.
• IEC 61727:2004, Photovoltaic systems: Characteristics of the utility interface.
• IEC 62116:2014, Anti-islanding test procedures for grid-tied PV inverters.
• IS 16221 (Part 1 and 2), Indian Standard for PV inverter safety, Bureau of Indian Standards.
• CEA Technical Standards for Connectivity to the Grid (Amendment) Regulations 2019, Central Electricity Authority of India.
• MNRE Approved List of Models and Manufacturers (ALMM), Ministry of New and Renewable Energy.
• PM Surya Ghar Muft Bijli Yojana, scheme guidelines, MNRE.
• EN 50530:2010, Overall efficiency of grid-connected photovoltaic inverters.
• NREL Technical Report TP-5D00-78195, On the Path to SunShot: Emerging Issues and Challenges in Integrating Solar with the Distribution System.