PART 1 OF 128 min read
How Solar Works: From Sunlight to Your Meter
A rooftop solar system converts sunlight into electricity through panels, converts it to usable AC power through an inverter, and settles the account with your electricity company through a net meter. This guide walks that journey end to end — no physics degree required.
The 60-Second Version
Sunlight hits silicon panels on your roof, which produce DC electricity. An inverter converts that DC into the 230 V AC your home runs on. Your appliances consume this solar power first; anything extra flows out through a net meter into the grid, earning you credits; anything short is drawn from the grid as usual. At the end of the billing cycle, you pay only for the net — grid units consumed minus solar units exported.
There are no moving parts, no fuel, and no daily operation. A correctly built system generates for 25 years or more, which is why solar is best understood not as an appliance but as a small power plant you own.
Step 1: Panels Turn Light into Current
Each panel is a weatherproof sandwich of silicon solar cells. When photons strike the silicon, they knock electrons loose — the photovoltaic effect — creating direct current. A typical modern panel is rated 440–575 Wp, and a 3 kW home system uses six to seven of them, needing roughly 240 sq.ft of shadow-free roof.
Panels are wired in series into "strings", raising the voltage to a level the inverter works with efficiently. This is also why shading matters so much: a shadow on one panel can drag down its whole string, the way a kink in one section slows an entire pipeline.
Step 2: The Inverter Makes It Usable
The inverter is the working brain of the system. It converts DC to AC, constantly hunts for the panels’ maximum power point as sun and temperature shift (MPPT), synchronises perfectly with grid voltage and frequency, and shuts down instantly during a power cut so it never back-feeds a line a technician believes is dead — a mandatory safety feature called anti-islanding.
That last point surprises many buyers: a standard on-grid system gives no backup during a power cut. Backup requires batteries and a hybrid inverter, which is a deliberate (and costlier) design choice, not a default.
Step 3: The Net Meter Settles the Account
After your DISCOM inspects the installation, it replaces your old meter with a bidirectional net meter that records energy in both directions. On a sunny afternoon your home may use 1 unit while the system makes 3 — the 2 surplus units export to the grid. At night you import as usual. The bill nets the two: import minus export.
Most well-sized systems settle annual bills 80–95% lower than before. The exact rules — how long credits carry forward, what happens to year-end surplus — vary by state, which is why our state-wise subsidy pages list your DISCOM’s specifics.
What a Complete System Contains
A quotation should account for every link in the chain — panels are only about half the cost of a quality installation.
The full bill of materials:
- Solar panels (ALMM-listed, DCR for subsidised homes)
- Inverter with remote monitoring app access
- Module mounting structure — galvanised steel or aluminium, wind-load designed
- DC and AC cables, correctly sized for under 2% loss
- DCDB and ACDB protection boxes with surge protection devices
- Earthing pits and lightning arrestor
- Net meter (installed by the DISCOM) and liaison paperwork
What Solar Does Not Do
Honest expectations prevent disappointment. Solar does not generate at night, does not give backup in a power cut without batteries, and does not deliver its nameplate wattage all day — a 3 kW system produces around 12 units on a good day, not 3 kW × 24 hours. Panels also lose a little output on very hot afternoons, which is normal physics, not a defect.
What it reliably does is convert an expense into an asset: electricity at an effective lifetime cost of ₹2.5–4 per unit against grid tariffs of ₹6–12, with a payback of typically 3–5 years.
Frequently Asked Questions
- Does a rooftop solar system work during a power cut?
- A standard on-grid system shuts down during outages for line-worker safety (anti-islanding). Backup requires a hybrid system with batteries, sized to the essential loads you want running.
- How much roof area does solar need in India?
- Roughly 80 sq.ft of shadow-free area per kW. A 3 kW home system needs about 240 sq.ft; shading from tanks, parapets, or neighbouring buildings reduces usable area and output.
- How many units will a 3 kW system generate per day?
- Across most of India, about 10–13 units per day averaged over the year — roughly 4 units per kW per day, varying with city, season, tilt, and cleanliness.