What would solar actually save you?
Built on your city's real slab tariffs and the exact PM Surya Ghar subsidy, and honest enough to tell you when payback is slow. Data verified: July 2026
See your numbers before you talk to anyone.
Most calculators flatter solar with a single savings figure. This one is honest: it shows the crossover point where solar overtakes the grid, the cost of not switching, and a 25-year view built on your city's real sunlight and tariffs.
Your details
Three inputs. The model does the rest, using city-specific sunlight and tariff data.
How this is calculated Data verified: Jul 2026
Your bill is converted to units using your city's actual slab tariff structure (the first units are cheap, the last expensive), and solar savings are valued at the top slabs it offsets, the way a real bill behaves. Sizing targets 80–90% of annual usage depending on roof type, capped by usable roof: independent house up to 6 kW, villa up to 10 kW, top-floor flat up to 3 kW. System cost is tiered by size (₹57,000–74,000/kW, small systems cost more per kW). Subsidy follows PM Surya Ghar exactly: ₹30,000/kW for the first 2 kW, ₹18,000 for the third, capped at ₹78,000. The 25-year path includes ₹600/kW/yr maintenance, one inverter replacement at year 12, 0.5%/yr panel degradation, and grid tariffs escalating 7.5%/yr (the decade trend is 7–9%). Figures are indicative, a site visit confirms the exact design.to your electricity board over the next 8 years, money you never get back. In Bengaluru, the same period of solar would already be paying you.
Grid vs solar, total spend over 25 years
Lines cross at year 3.4This is an indicative model. Want the exact numbers for your roof? Verify your DISCOM's exact net-metering rules on the state subsidy page before you commit.
Lock in my real estimateA rupee-by-rupee comparison, by home size.
Most people compare installation cost to a monthly bill, the wrong metric. The honest comparison is lifetime: post-subsidy cost, 25 years of generation, rising grid tariffs, and what you net at the end.
| Home | Monthly units | Grid bill (2025) | Solar size | Post-subsidy cost | Annual saving | Payback | 25-yr net |
|---|---|---|---|---|---|---|---|
| 1BHK / Small | 100–150 | ₹900–1,400 | 1–1.5 kW | ₹40k–70k | ₹10k–16k | 3.5–4.5 yrs | ₹2.5–3.5L |
| 2BHK / Medium | 200–280 | ₹1,800–2,600 | 2–2.5 kW | ₹85k–1.0L | ₹20k–28k | 3.5–4.5 yrs | ₹4.5–6L |
| 3BHK / Large | 300–450 | ₹2,800–4,200 | 3–4 kW | ₹1.1L–1.7L | ₹30k–45k | 3.5–4.5 yrs | ₹7–10L |
| Villa / 4BHK+ | 500–900 | ₹5,000–9,500 | 5–8 kW | ₹2.3L–3.8L | ₹55k–90k | 3.5–5 yrs | ₹12–19L |
Assumes 7.5% annual tariff rise and 0.5% annual panel degradation. Subsidy per PM Surya Ghar Muft Bijli Yojana 2025–26.
Modern panels run on diffused light, not only direct sun, typically 20–40% output even when overcast. Net metering banks your sunny-day surplus as credits to draw down later. Bengaluru averages 5.1 peak sun hours/day, Mumbai 4.8, Chennai 5.4, Delhi 5.5, every major Indian city makes rooftop solar financially compelling.
Your tariff is only the visible cost. Add inverter-battery replacement (₹18,000 every ~3.5 years), appliance damage from voltage swings (₹5k–15k/decade), and the productivity loss from daily outages. Solar with net metering or storage removes all three.
How sizing actually works, and when bigger backfires
The maths is simpler than installers make it sound. One kilowatt of panels produces roughly 30 × your city's sun-hours × 0.75–0.80 units a month, the last factor is real-world performance after dust, heat and wiring losses. In most Indian cities that lands between 100 and 125 units per kW per month, and needs about 80–100 sq ft of shadow-free roof. So a home using 350 units a month is a ~3 kW home, not the 5 kW a commission-hungry salesman might suggest.
Three kilowatts is also where the subsidy maths peaks: the ₹78,000 cap is fully earned at 3 kW, and every kilowatt after that is subsidy-free. Bigger systems still make sense for big consumers, cost per kW falls as systems grow, but oversizing past your consumption backfires in two ways. Many DISCOMs cap your system at your sanctioned load, and several states credit surplus exports at a lower rate than the tariff you pay, which quietly stretches the payback on those extra panels. The honest rule: size to 90–100% of your annual consumption, and only go beyond it if an EV or an extension is genuinely planned.
One spec that confuses everyone: your panel capacity can legitimately exceed your inverter's rating. A DC-to-AC ratio of 1.1–1.25 is deliberate engineering, panels rarely hit their nameplate peak, so a 4.4 kW array on a 4 kW inverter wastes almost nothing and saves real money. It's not a corner being cut.
What actually moves your payback
Ranked by impact: first, your top-slab tariff, solar savings are valued at the most expensive units you stop buying, which is why high-bill homes in slab-heavy cities recover fastest. Second, self-consumption: a unit used at noon is worth full tariff; a unit exported may earn less, so daytime usage (or a well-set timer on the water heater) genuinely shortens payback. Third, your capital cost per kW, which is exactly why the quote-reading habit matters. Fourth, and less than most people think: tariff escalation.
Here is the same worked example, a 3.5 kW system in Bengaluru on a ₹3,500 bill, net cost ₹1.4 L after subsidy, run at three different tariff-escalation assumptions. At 5% a year, payback stretches only to about 3.6 years; at our standard 7.5% it's the 3.4 years the calculator shows; at 10% it's still about 3.4. Notice what happens: the payback barely moves, because it arrives so early that escalation hasn't had time to matter. The 25-year cumulative benefit is a different story, in a straight projection it swings from roughly ₹14½ lakh at 5% to over ₹31 lakh at 10% (the calculator's own 25-year figure runs a little higher still, since it models the inverter swap and degradation in finer detail). Escalation isn't a reason to doubt solar; it's the reason the second decade is where the real money is.
Everything above is already inside this calculator's numbers: 0.5% annual panel degradation, ₹600 per kW per year of cleaning and maintenance, and an inverter replacement around year twelve. When our payback says 3.4 years, that's after those deductions, not before.
You've seen your numbers. Explore your options.
GreenCompare Solar is an independent educational platform. No forms, no sales calls, decide at your own pace.