Customers ask for "solar" but mean very different things. One wants a lower bill, one wants the fans to keep running during load-shedding, and one has a farmhouse with no grid at all. Before you size anything, you need to know which of the three system types fits.
The building blocks
Every rooftop system has the same core parts. Some are added or removed depending on the type.
| Part | Job | Covered in |
|---|---|---|
| PV modules (the array) | Turn sunlight into DC electricity | m01, m04 |
| Mounting structure | Hold the modules at the right angle against wind | m05 |
| DC cables, MC4 connectors, DCDB | Carry and protect DC power from the roof | m04, m06 |
| Inverter | Convert DC to 230/415 V AC, track maximum power, sync with the grid | m04 |
| ACDB | AC protection: MCB, RCCB, surge protection | m04, m06 |
| Meters | Net meter (and sometimes a generation meter) | m04, m08 |
| Earthing and lightning protection | Safety for people and equipment | m06 |
| Battery (hybrid and off-grid only) | Store energy for night or power cuts | m07 |
| Monitoring | Wi-Fi or data logger showing generation | m04 |
1. On-grid (grid-tied) systems
Modules feed an on-grid inverter, which pushes AC power into the house wiring. Loads use solar power first. Any surplus flows out through the net meter to the DISCOM grid, and at night the house draws from the grid as usual. The net meter records import and export, and the bill is settled on the difference (the exact rules depend on the state; see module m08).
The key fact customers miss: an on-grid system switches off when the grid fails, even at noon. This is called anti-islanding. It protects linemen working on a line they believe is dead. The inverter waits until the grid returns and is stable, then reconnects automatically.
Strengths:
- Lowest cost per kW, no batteries to replace.
- Eligible for PM Surya Ghar central financial assistance for homes: ₹30,000 per kW for the first 2 kW and ₹18,000 for the third kW, capped at ₹78,000 (2024 guidelines; the scheme runs to FY 2026-27, so check the current notification).
- Highest lifetime savings for most city homes with reliable supply.
It suits most urban homes in Pune, Ahmedabad, Jaipur or Chennai where power cuts are short and rare.
2. Hybrid systems
A hybrid inverter connects to the modules, a battery, the grid and a separate backup (essential) load circuit. Normally it behaves like an on-grid system and can export surplus. When the grid fails, it disconnects from the grid (anti-islanding still applies) and runs the backup loads from solar and battery.
Points to explain:
- Backup covers only the circuits wired to the backup port: usually lights, fans, fridge, Wi-Fi and a TV. Air conditioners and geysers are normally left out because they drain the battery fast.
- Batteries add cost and have a life of their own (LFP batteries are often warranted for around 10 years or a set number of cycles; read the warranty terms).
- Under PM Surya Ghar, central assistance is calculated on the solar kW; the battery is not subsidised (check the current guidelines).
- With time-of-day tariffs spreading, a battery can also shift solar energy into expensive evening hours (module m07).
It suits homes with frequent cuts (many towns in UP, Bihar, smaller Maharashtra towns), work-from-home professionals, and clinics or shops that cannot stop.
3. Off-grid systems
No grid connection at all. Modules charge a battery through a charge controller, and an off-grid inverter or PCU (power conditioning unit) supplies the loads. Everything the site uses must come from the sun, so the battery must cover nights and cloudy spells.
- Sized for the worst month (for example July in Maharashtra), not the average.
- Batteries are the largest lifetime cost. Lead-acid tubular batteries are still common in rural kits; LFP is taking over.
- Typical users: farmhouses, remote homestays, telecom shelters, pump houses and islands.
Side-by-side comparison
| On-grid | Hybrid | Off-grid | |
|---|---|---|---|
| Works in a power cut | No | Yes, backup loads only | Yes (no grid anyway) |
| Battery | None | Yes | Yes, larger |
| Export to grid | Yes | Yes | No |
| Relative cost per kW | Lowest | Higher | Highest |
| PM Surya Ghar CFA | Yes (on solar kW) | Solar part only | Not under the rooftop scheme |
| Maintenance | Cleaning, checks | Plus battery care | Plus battery care and replacement |
| Best for | City homes with reliable grid | Frequent cuts, critical loads | No grid |
Worked example: same house, two choices
A family in Indore uses 300 units a month and faces about one hour of cuts a day in summer.
- On-grid 3 kWp: about ₹60,000 per kW installed before subsidy (Sunlectric benchmark, October 2026) gives ₹1,80,000. Less CFA ₹78,000, the customer pays about ₹1,02,000. Generation ≈ 3 × 1,526 = 4,578 units a year, covering their 3,600 units.
- Hybrid 3 kWp with a 5 kWh LFP battery: the solar part attracts the same ₹78,000, but the hybrid inverter and battery add a significant amount. Get a current price from your distributor and present both options in writing.
For one hour of cuts, many families are happier with on-grid solar plus their existing inverter-battery set for lights and fans. For four hours of cuts, the hybrid earns its cost. Ask the customer, show the numbers, and let them choose.
Key points
- Every system has modules, a structure, DC and AC protection, an inverter, meters and earthing; hybrid and off-grid systems add a battery.
- On-grid systems shut down in a power cut because of anti-islanding protection, even in full sun.
- Hybrid systems back up only the loads wired to the backup circuit.
- On-grid is the cheapest and most common choice for city homes and attracts PM Surya Ghar CFA.
- Ask about outage hours and critical loads before choosing the system type.
Check yourself
- Why does an on-grid inverter switch off during a grid outage?
- A customer with a hybrid system complains that the AC stopped during a power cut. What is the likely reason?
- Which system type would you suggest for a farmhouse 3 km from the nearest power line?
Answers
- Anti-islanding protection stops it feeding a dead grid, protecting line workers and equipment.
- The AC is on the normal load circuit, not the backup circuit, which is usual because ACs drain the battery quickly.
- Off-grid, sized for the worst month, unless a grid connection is planned soon.