1. On-Grid Solar Inverter
An on-grid solar inverter is connected to solar panels and the electricity grid. It supplies solar power to the home or building and can export surplus electricity to the grid when permitted.
Main components:
- Solar panels
- On-grid solar inverter
- AC and DC protection devices
- Bidirectional or net meter, as applicable
- Electricity grid
Working process:
- Solar panels convert sunlight into DC electricity.
- The inverter converts DC electricity into AC electricity.
- The AC power runs household appliances.
- Extra electricity may be exported to the grid.
- When solar production is insufficient, electricity can be drawn from the grid.
Advantages:
- Usually does not require batteries.
- Lower initial cost than a comparable battery-based system.
- Can reduce electricity bills.
- Excess power may receive credit under applicable net-metering rules.
Disadvantages:
- Standard grid-tied systems shut down during a grid outage for safety.
- They generally cannot provide backup power without suitable additional equipment.
2. Off-Grid Solar Inverter
An off-grid solar inverter operates independently of the electricity grid. It is commonly used in remote areas where grid electricity is unavailable or unreliable.
Main components:
- Solar panels
- Off-grid inverter
- Battery bank
- Solar charge controller (built into some inverters)
- DC and AC protection devices
- Household electrical loads
Working process:
- Solar panels produce DC electricity from sunlight.
- Solar power supplies the loads and charges the batteries, depending on the system design.
- The battery stores energy for later use.
- The inverter converts DC electricity into AC electricity.
- Appliances can operate using solar power and stored battery energy.
Advantages:
- Can supply electricity where grid power is unavailable.
- Battery backup can power appliances at night.
- Can provide power during grid outages because it does not depend on the grid.
Disadvantages:
- Batteries increase the installation cost.
- Battery capacity limits how long appliances can operate.
- Batteries require suitable maintenance or eventual replacement, depending on their type.
3. Difference Between On-Grid and Off-Grid Inverters
| Feature | On-Grid Inverter | Off-Grid Inverter |
|---|---|---|
| Electricity grid | Connected | Not required |
| Battery | Usually not required | Generally required |
| Night operation | Grid supplies power when needed | Battery supplies power |
| During power cuts | Normally shuts down | Can continue supplying supported loads |
| Initial cost | Generally lower | Generally higher |
| Excess solar power | May export to grid | Usually charges batteries or supplies loads |
| Best use | Homes with reliable grid supply | Remote areas and independent power systems |
4. Basic Solar Inverter Diagram
On-grid system
Solar Panels (DC)
On-Grid Inverter
AC Distribution Board
Supplies loads and connects to the grid through the approved system.
Off-grid system
Solar Panels (DC)
Charge Controller / Off-Grid Inverter
Battery Bank
AC Loads
Exact power flow depends on the inverter design; some units connect the battery and loads through separate terminals.
5. Important Inverter Specifications
When selecting a solar inverter, check:
- Rated power: e.g., 1 kW, 3 kW or 5 kW.
- Input voltage: Solar panel DC voltage range.
- Output voltage: Commonly 230 V AC single-phase in India.
- Frequency: Commonly 50 Hz.
- Battery voltage: For example, 12 V, 24 V, 48 V, or a specified high-voltage battery.
- Efficiency: How effectively the inverter converts electrical energy.
- Protection: Overload, short circuit, overvoltage and temperature protection.
Safety note: Solar panels can generate dangerous DC voltage in sunlight. Use correctly rated cables, isolators, earthing and protection devices, and follow the manufacturer’s wiring diagram.
6. Conclusion
An on-grid inverter is suitable for reducing electricity bills when a grid connection is available. An off-grid inverter is suitable when independent electricity and battery backup are required. A hybrid inverter combines grid connection and battery support, depending on its design and configuration.
