A grid tied inverter converts DC solar power into AC electricity synchronised with the utility grid, allowing you to feed excess solar energy back to the grid and receive credits on your electricity bill through net metering. In India, with MNRE subsidies covering 20-40% of rooftop solar costs, grid-tied solar is the fastest-growing renewable energy segment. This guide covers grid-tie fundamentals, Indian net metering policies, and anti-islanding safety requirements.
Grid-Tied Inverter Basics
A grid-tied (or grid-tie) inverter does not use batteries. It converts solar DC directly to 230V/50Hz AC synchronised with the grid. When your panels produce more than you consume, the excess flows to the grid. When you need more than panels produce, you draw from the grid.
Key technical requirements:
- Output exactly matches grid voltage (230V RMS) and frequency (50Hz)
- Phase-locked loop (PLL) synchronises inverter output with grid waveform
- Maximum Power Point Tracking (MPPT) for solar panels
- Anti-islanding detection (disconnects within 2 seconds if grid fails)
- Power factor near unity (>0.99)
How Grid-Tie Feeding Works
Solar panels → DC → Grid-tie inverter → AC (synchronised)
↓
Home loads ← Grid
↓
Excess → Bidirectional meter → Grid
Net metering calculation:
Month consumption: 300 kWh from grid
Month generation: 200 kWh from solar
Export to grid: 50 kWh (when generation > consumption)
Net bill: (300 - 200) x tariff + fixed charges
Or: (300 - 50 credit) x tariff (depending on state policy)Indian Net Metering Rules
- Eligibility: Residential and commercial consumers with rooftop space
- Capacity limit: Up to sanctioned load or 500kW, whichever is lower
- Metering: Bidirectional (net) meter provided by DISCOM or consumer
- State variations: Each state has different tariffs, credit rates, and policies. Delhi, Maharashtra, Gujarat, Karnataka, and Tamil Nadu have the most favourable policies.
- Subsidy: MNRE PM Surya Ghar scheme provides Rs.30,000-78,000 subsidy for 1-10kW residential rooftop solar.
Anti-Islanding and Safety
Anti-islanding is the most critical safety feature: the inverter must disconnect from the grid within 2 seconds if the grid fails. Without this, the inverter would energise dead grid lines, endangering utility workers.
- Passive methods: Monitor voltage and frequency deviations. If V or f exceeds thresholds, disconnect.
- Active methods: Inject small perturbations and detect grid impedance changes.
- Standard: IEC 62116 / IS 16169 for Indian grid-connected inverters.
WARNING: DIY grid-tied inverters are illegal in India without BIS certification and DISCOM approval. Use commercially certified inverters (Growatt, Goodwe, Havells, Deye) for grid-connected installations. This article is for educational understanding only.
Key Components
- Solar panels: Monocrystalline 400-540W panels (Rs.15-25 per watt)
- Grid-tie inverter: Growatt 3-5kW (Rs.25,000-40,000) or Havells 3kW (Rs.30,000-45,000)
- Bidirectional meter: Supplied by DISCOM or purchased (Rs.2,000-5,000)
- DC disconnect: Isolator switch between panels and inverter
- AC disconnect: MCB/MCCB between inverter and distribution board
FAQ
How much does a grid-tied solar system cost in India?
For a 3kW system (typical home): Rs.1.5-2.5 lakh before subsidy. After PM Surya Ghar subsidy (Rs.78,000 for 3kW): Rs.72,000-1.7 lakh. Payback period: 3-5 years depending on state tariff and consumption pattern.
What happens to my grid-tie system during a power cut?
The inverter shuts down (anti-islanding). Your solar panels produce no usable power during grid outages. To have backup, add a hybrid inverter with battery storage (additional Rs.30,000-80,000 for batteries).
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