If you own a 3 BHK home in Noida and your summer bill crosses ₹4,000, this is the only number that matters: what does a rooftop solar system actually put back in your pocket each month? Not "savings" in the abstract. Rupees. Here is the month-by-month math for a typical 3 kW system, using real generation figures and the current PM Surya Ghar subsidy.
The system we are costing
A 3 kW grid-connected rooftop system is the sweet spot for most Noida homes. It needs about 300 sq ft of shadow-free roof (roughly 100 sq ft per kW) and generates 360 to 450 units a month, depending on season, with peak output from March to June and a dip during the monsoon and dense winter fog.
Where the rupees come from
Three levers move your bill:
- Self-consumption. Every unit your panels make and you use immediately is a unit you do not buy from NPCL. Daytime loads, fans, fridge, RO, a daytime AC, are offset first.
- Net metering. Units you export through a bidirectional meter are credited and knock down your next bill.
- The subsidy. PM Surya Ghar cuts your upfront cost, which shortens payback.
A month-by-month picture
Take a home with a ₹4,000 monthly bill, roughly 500 units of consumption. A 3 kW system covering 360 to 450 of those units offsets the large majority of the bill. In high-generation months (March to June) the system can wipe out almost the entire bill and bank export credits; in monsoon and peak winter, generation dips and you draw a little more from the grid, spending the credits you banked earlier. Across a full year, this is where the "up to 90% lower bills" figure comes from: it is an annual average, not a flat monthly guarantee.
The subsidy that shortens payback
For a 3 kW system, the central PM Surya Ghar subsidy is the full ₹78,000 (₹30,000 per kW for the first 2 kW, ₹18,000 for the third). UP residents add a UPNEDA top-up of about ₹15,000 per kW, capped at ₹30,000. After the subsidy, a well-designed 3 kW system typically pays for itself in about 4 to 5 years, then runs largely free for the remaining 20 of its 25-year panel life.
What changes your numbers
- Roof shading. One shaded panel can drag down a whole string, so a clean, unshaded layout matters more than raw panel count.
- Direction and tilt. South-facing, correctly tilted arrays generate more.
- Cleaning. Dust in Noida can cut output 10 to 30%; a wash 2 to 4 times a year protects your savings.
- Your usage pattern. The more you can shift heavy loads to daytime, the more you self-consume and save.
Frequently asked questions
How many panels is 3 kW?
With modern panels, roughly 6 to 8 panels, fitting in about 300 sq ft of shadow-free roof.
Will it cover my whole bill?
Often most of it on an annual average. Exact coverage depends on your consumption, roof, and how much you use during daylight.
How fast is payback?
Usually about 4 to 5 years after the subsidy for a 3 kW residential system in Noida.
Can I go bigger than 3 kW?
Yes, but the central subsidy caps at ₹78,000 for 3 kW and above, so sizing past 3 kW is about your consumption, not extra subsidy.
How do I get exact numbers for my roof?
Book a free site visit. We measure your roof, shading, and 6 to 12 months of bills and give you a real generation and savings estimate.
SIA Solar
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