Estimate the right system size, installed cost after the PM Surya Ghar subsidy, monthly savings and payback period for your home or business. Pick on-grid, off-grid or surplus-space solar below — the calculator uses your state's electricity tariff and buyback rate and runs entirely in your browser.
An on-grid (grid-tied) system connects your panels directly to the utility grid through a bi-directional meter. There are no batteries. When your panels produce more than you consume, the excess flows back to the grid and your meter runs backwards.
How the money works: Under net metering you're billed only on net consumption. Generate 400 units, use 300, and you pay for zero while carrying a 100-unit credit. Some states pay cash for surplus at a buyback rate (₹2–3.5/kWh); others only offset your bill.
Where it wins:
The catch: During a grid outage an on-grid inverter shuts down automatically — even in bright sunlight. This is mandatory anti-islanding safety so linemen repairing the grid aren't electrocuted by your exported power. If you have 4+ hour daily outages, that's a real problem.
Best for: Urban and semi-urban homes with reliable grid supply and high bills. Under 2 hours of daily outage? This is almost always right.
An off-grid system is self-contained. Panels charge a battery bank during the day; the battery powers your home at night and through outages. You're either not connected to the DISCOM at all, or you keep the connection purely as backup.
How the money works: You're not selling anything. Your return is the electricity bill you avoid entirely, plus the diesel generator you stop running. In areas with 6+ hours of daily load-shedding, DG fuel savings alone often justify the system.
Where it wins:
The catch: Batteries are expensive and they die. Lead-acid lasts 4–6 years; lithium (LFP) lasts 10–15 but costs 2.5× upfront. Budget for a full replacement in year 6 with lead-acid. There is also no PM Surya Ghar subsidy for off-grid residential — the scheme requires grid connection and net metering.
Sizing is different: You size for your worst day, not your average. Two consecutive cloudy days with no grid means the battery carries the whole load. Off-grid systems run 30–50% oversized versus on-grid.
Best for: Rural homes, farmhouses, 4+ hours of daily outage, or anyone who cannot tolerate a power cut.
A hybrid system is grid-tied with a battery. It exports surplus like on-grid, but keeps a small battery (2–5 kWh) to run essential loads during outages — lights, fans, fridge, router.
The battery is deliberately undersized. You aren't trying to run the AC through a 6-hour cut; you're keeping the fridge cold and the lights on. That keeps cost far below true off-grid.
Subsidy nuance: Several DISCOMs let the solar portion claim PM Surya Ghar subsidy as long as export capability and a net meter are installed. The battery is never subsidised. Rules vary — confirm before assuming.
Best for: Urban homes with occasional but disruptive outages, home offices, medical equipment. Costs roughly 1.5–1.7× an equivalent on-grid system.
Configure this by choosing On-Grid and enabling battery backup in Step 2.
This is for people who have more space than they need power. A big terrace, a warehouse roof, a shed, half an acre of unused land behind the house. Instead of sizing solar to your own bill, you fill the space and sell the surplus.
The core idea: Your own consumption might need 3 kWp. But you have room for 12 kWp. Those extra 9 kWp generate power you'll never use — so it goes to the grid, and the DISCOM pays you for it.
What you actually earn: Self-consumed units are worth your full tariff (₹5–7.5/kWh) because you avoid buying them. Exported units earn the buyback rate (₹2–3.5/kWh), which is always lower. So the economics are strongest when you use as much as you can and sell the remainder.
Three practical scales:
The three real constraints:
Realistic returns: A 10 kWp rooftop in a ₹7/kWh state with 50% self-consumption returns roughly 14–16% annually and pays back in 5–6 years. Push self-consumption higher (run the AC, charge an EV during the day) and it improves sharply.
Best for: Homeowners with large terraces, small businesses with warehouse roofs, or anyone sitting on an idle plot near an existing electricity connection.
| On-Grid | Off-Grid | Surplus Space | |
|---|---|---|---|
| Sized to | Your consumption | Your worst day | Your available space |
| Battery required | No | Yes | No |
| Cost per kWp | ₹55–70k | ₹95–140k | ₹50–65k (scale discount) |
| PM Surya Ghar subsidy | ✓ Max ₹78,000 | ✗ Not eligible | ✓ Max ₹78,000 (≥3kWp) |
| Works during blackout | ✗ Auto shutdown | ✓ Full backup | ✗ Auto shutdown |
| Sell power back | ✓ Small surplus | ✗ No export | ✓ Primary income |
| Typical payback | 3–5 yrs | 6–9 yrs | 5–7 yrs |
| Maintenance | Low | Medium (battery swap yr 6) | Low–Medium |
| DISCOM approval | Required | Not needed | Required + load check |
| Main constraint | Your bill size | Battery cost | Sanctioned load cap |
| Best for | Urban homes, stable grid | Rural, outage-prone | Big terraces, sheds, plots |
Every number above is worked out in your browser from a handful of transparent assumptions. Here is exactly what the rooftop solar calculator does with your inputs, so you can check it against any installer's quote.
In bill mode, monthly units are divided by 30 to get kWh per day. If you enter a rupee amount instead, it is first divided by your tariff (₹/kWh) to estimate units. In appliance mode, each appliance's watts × quantity × hours per day are added up and divided by 1,000. Appliances you exclude, or high-draw loads you switch off, are left out.
System size = daily use ÷ peak sun hours for your state, rounded up to the next 0.1 kW (minimum 0.5 kW). Peak sun hours range from about 4.5 (Kerala, West Bengal) to 6.5 (Rajasthan); India averages 4.5–5.5. Off-grid systems are oversized by 35% to cover cloudy days and battery charging losses. For surplus space, size is set by your shadow-free area and panel efficiency instead, and capped by your sanctioned load × the DISCOM's permitted percentage.
Daily generation = kWp × peak sun hours × 0.78. The 0.78 performance ratio accounts for real-world losses from heat, dust, wiring and the inverter. In practice, 1 kW of panels produces about 4 units a day, or roughly 1,400 units a year, at 5 peak sun hours (see solar generation per kW by state). Panel area is estimated as kWp × 100 ÷ panel efficiency (in m²), which works out to roughly 55 sq ft of panels per kW for Mono PERC. Leave extra room for walkways and shade-free spacing. For panel counts by monthly usage and state, see how many solar panels do I need.
Installed cost starts from benchmark rates of ₹65,000 per kW for on-grid and ₹52,000 per kW for off-grid (before batteries). These are split into panels (42%), inverter (18% on-grid, 22% off-grid), mounting structure (12%), balance of system such as cables and protection (14%) and installation labour (14%). Panel cost is then adjusted for the technology you choose (TOPCon +22%, bifacial HJT +38%, and so on), and on-grid systems add ₹8,000 for the net meter. Batteries are priced per kWh of usable storage needed for your days of autonomy. Surplus-space projects use separate per-kW rates, with scale discounts above 25, 50 and 100 kW. Our solar panel cost guide compares these benchmarks with 2026 market quotes for 1–10 kW.
For residential on-grid systems, the solar subsidy calculator applies the central PM Surya Ghar Muft Bijli Yojana support: ₹30,000 per kW for the first 2 kW, ₹18,000 for the third kW, capped at ₹78,000 for any system of 3 kW or more. Off-grid systems and commercial connections receive no residential subsidy. Commercial roofs and ground mounts instead show the year-one tax benefit of 40% accelerated depreciation, assuming a 30% tax rate (our commercial rooftop solar guide covers sizing, ToD tariffs and payback for businesses). See the PM Surya Ghar subsidy guide for slab-by-slab examples and how to claim it.
On-grid, the calculator assumes you use 65% of what the panels produce, up to your own consumption, and export the rest. Units you use save your full tariff, while exported units earn only your DISCOM's buyback rate. Valuing every export at the buyback rate is cautious, because under net metering exports offset within a billing cycle are worth your full tariff. Tariff and buyback rate are both prefilled from state-wise electricity tariffs and can be edited. Off-grid savings also include an allowance for generator diesel you no longer buy. Payback = net cost after subsidy ÷ first-year benefit. The surplus-space path also projects 25 years of cash flow with 3% annual tariff growth, panel degradation and 1% yearly maintenance.
At ₹7 per unit, a ₹3,000 bill is about 430 units a month, or 14.3 kWh a day. Divided by Delhi's 5.5 peak sun hours, that is a 2.6–2.7 kW system (2.6 kW if you enter the rupee amount, 2.7 kW if you enter 430 units, because the result is rounded up to the next 0.1 kW). In a lower-sunshine state with 4.5 hours, it is closer to 3.2 kW. As a rule of thumb, at 5 peak sun hours the calculator sizes about 1 kW for every 150 units of monthly use. Enter your own bill above for your state's figure.
Using the calculator's benchmark rates, a 3 kW on-grid system costs about ₹2.0–2.1 lakh before subsidy with polycrystalline or Mono PERC panels, including the net meter. After the ₹78,000 PM Surya Ghar subsidy, you pay roughly ₹1.25–1.32 lakh. Quotes typically vary 15–25% by city and installer, and premium panels cost more.
For most homes on grid-connected solar, it is roughly 4–8 years in most states, and up to about 10 years where tariffs are low. For example, the Delhi household above, with a 2.7 kW system costing ₹1.17 lakh after a ₹72,600 subsidy, generates about 4,200 units a year. It saves around ₹24,000 a year in bill savings and export credit, a payback of about 4.8 years. Higher tariffs, more daytime use and sunnier states all shorten payback. Panels are usually warrantied for 25–30 years, so most of their life is free electricity.
No. The PM Surya Ghar subsidy is for grid-connected rooftop systems on residential connections, installed through a vendor registered on the national portal. Off-grid battery systems and commercial or industrial connections are not eligible, so the calculator shows ₹0 subsidy for them. Businesses can instead claim accelerated depreciation.
Under net metering, your DISCOM credits exported units at a buyback rate that is usually ₹2–3.5 per unit, well below the ₹4–7.5 you pay for grid power. Every unit you use yourself is worth your full tariff. That is why shifting loads such as washing, water heating or EV charging to daytime often improves returns more than adding panels.
The panels themselves take about 55 sq ft per kW with Mono PERC (about 50 sq ft with TOPCon, 67 sq ft with polycrystalline). Including walkways and spacing to avoid shading, plan for roughly 80–100 sq ft of shadow-free roof per kW. A typical 3 kW home system therefore needs about 240–300 sq ft.
It is designed for a realistic first estimate, not a binding quote. Sizing and generation use state-level sunshine data and a standard loss factor, while costs use national benchmark rates. Your actual quote depends on roof type, cable runs, panel and inverter brand, and local DISCOM charges. Use the estimate to judge whether quotes are in the right range.