Solar Calculator – Estimate Your Solar Savings & System Cost

A solar calculator turns one number you already know — your monthly electricity bill — into a realistic picture of what rooftop solar can do for your property. Our calculator first converts your bill into an estimated electricity consumption in units (kWh), using an effective per-unit tariff assumption of ₹8.5 for homes and ₹9.5 for businesses, which reflects typical blended tariffs in Maharashtra. It then scales that monthly consumption up to a full year, because solar generation changes with the seasons while your annual consumption is the steadier number.

Next it sizes a system. Maharashtra rooftops typically generate around 1,450 units per kW of installed solar per year, so the calculator divides your annual consumption by that yield — slightly reduced to keep headroom for monsoon months and panel ageing — to arrive at a recommended capacity in kW. Your available rooftop area acts as a hard physical cap: at roughly 50 sq.ft. per kW, the calculator will never recommend a system your roof cannot physically host.

Finally, it prices the result. Estimated generation is valued at the same per-unit tariff to produce savings, the PM Surya Ghar subsidy is applied for homes, and the net cost divided by annual savings gives the payback period. The full calculation chain looks like this:

1. Monthly electricity bill → estimated units consumed
2. Monthly units → estimated annual consumption
3. Annual consumption + solar yield → recommended system size
4. System size + rooftop area → final capacity (roof-capped)
5. Capacity → estimated monthly and annual generation
6. Units offset × tariff → estimated savings and remaining bill
7. System cost − subsidy = net cost → estimated payback period

Because every step is a documented calculation — not a fixed percentage of your bill — you can question, verify and adjust each assumption. That transparency is deliberate: an estimate you can audit is worth more than a number you must simply trust.

The honest answer: your consumption decides, and your roof confirms. As a worked example, a ₹3,000 monthly bill corresponds to roughly 353 units per month at typical Maharashtra tariffs — which usually points to a 2.7–3.0 kW system. A ₹5,000 bill generally lands near 4.5 kW, ₹8,000 near 7.5 kW, and ₹10,000 near 9–9.5 kW. Larger homes and commercial premises scale the same way until the available roof area becomes the limiting factor — which is exactly why the calculator asks for both numbers and shows an alert whenever your roof caps the recommendation.

The table below shows what commonly installed system sizes look like under the same assumptions used by the calculator. Treat generation as a planning estimate, not a guarantee — actual output varies with your exact location, roof orientation, shading and system performance.

Note what the table deliberately does not include: guaranteed savings figures per system size. Savings depend on how much of the generated power you actually use, your tariff and your net-metering arrangement — so the honest way to estimate them is to enter your own bill in the calculator above. If you are counting panels rather than kilowatts: with modern 575–625 Wp modules, a 3 kW system typically uses 5–6 panels, and each kW of capacity needs roughly two of them.

A typical rooftop solar installation in Maharashtra may cost approximately ₹60,000–₹70,000 per kW before applicable subsidy, depending on the system and installation requirements. In practice that means a 3 kW system — the most common residential size — usually falls around ₹1,80,000–₹2,10,000 before subsidy, and around ₹1,17,000–₹1,32,000 net after the full ₹78,000 PM Surya Ghar subsidy for homes. A 5 kW system typically works out to ₹3,00,000–₹3,50,000 before subsidy, with the same ₹78,000 subsidy cap applied for residential connections.

These figures are planning estimates, not a quotation. Your actual price can move meaningfully in either direction based on:

• Panel brand, efficiency and module technology
• Inverter brand and warranty tier
• Overall system size
• Mounting structure type and roof height
• Site conditions and accessibility
• Electrical requirements and wiring scope
• Installation complexity and labour

The only way to get a firm number is a site survey, where the roof, wiring and consumption pattern are assessed directly. You can request one without any obligation — and if you want the full context first, explore our residential, commercial and industrial solar installation services.

Savings depend on several variables working together — and any calculator or salesperson who quotes you a single universal figure is skipping the details. The main factors are:

• Your electricity consumption, in units per month
• Your applicable tariff, which rises with usage slabs
• The size of the solar system installed
• Actual solar generation at your location
• Your consumption pattern — daytime use versus evening use
• Net-metering and billing rules that apply to your connection
• Fixed charges, meter rent and taxes that stay on every bill
• Shading, dust and real-world system performance

Our calculator models these factors conservatively. It values only the units your system actually offsets at your effective tariff, and it never claims your entire bill disappears — fixed charges, meter rent and taxes remain on every MSEDCL or other DISCOM bill. That is why the results panel shows an estimated remaining monthly bill alongside the savings, so the picture you see is the one you will actually live with.

For most right-sized residential systems in Maharashtra, the energy portion of the bill — the part solar can genuinely offset — is the large majority of the total. Enter your own bill and roof area in the calculator above to see what that means for your property specifically, including the estimated payback period.

Residential consumers in Maharashtra can claim the PM Surya Ghar: Muft Bijli Yojana central subsidy for grid-connected rooftop solar. The current structure is progressive:

• First 2 kW: ₹30,000 per kW
• Additional capacity up to 3 kW: ₹18,000 per kW
• Maximum: ₹78,000 per household
• Above 3 kW: no additional central subsidy

Calculated progressively: a 1 kW system receives ₹30,000, a 2 kW system receives ₹60,000, and any system of 3 kW or larger receives the full ₹78,000 cap — which is why the calculator shows the same subsidy for 3 kW, 5 kW and 10 kW homes. Commercial and industrial connections are not eligible for this central subsidy, so the calculator applies it to home systems only.

The subsidy is claimed through the national PM Surya Ghar portal after your system is installed and net-metered, and the amount is credited directly to your bank account by the government after verification. Eligibility and the final sanctioned amount are subject to current scheme rules and approval — the figure shown in the calculator is an estimate based on today’s published guidelines. For documents, eligibility details and the step-by-step application process, see our solar subsidy assistance guide.

As a planning rule of thumb, budget roughly 50 sq.ft. of shadow-free roof area per kW of capacity — the same assumption the calculator uses when your roof caps the recommended system size. A 3 kW system therefore needs around 150 sq.ft., and a 5 kW system around 250 sq.ft. With modern high-efficiency modules, each kilowatt typically means about two panels, so panel count scales directly with system size.

Real requirements vary. Panel technology and efficiency, module wattage, roof layout, required setbacks, walkways, elevated structure design and obstructions like water tanks, parapets, vents and neighbouring shadows all change how much usable area your roof really offers. Two roofs with identical square footage can host very different systems — which is why the calculator treats roof area as a cap on its recommendation, and why a physical site survey remains the final word on what your roof can support. If your available area is limited, the calculator will flag it and size the system to what the roof can genuinely host.

It is accurate as an estimate — and it is not a quotation. Those two statements matter equally. The calculator is deterministic: the same inputs always produce the same output, from a documented chain of assumptions (effective tariff of ₹8.5/₹9.5 per unit, 1,450 units per kW per year, 50 sq.ft. per kW, ₹60,000–₹70,000 per kW before subsidy, and a ~12% non-energy charge allowance). Nothing is hidden and nothing is tuned to flatter the result.

What the calculator cannot know is how reality will drift from those assumptions. Electricity tariffs change. Monsoon years differ. Shading, roof orientation, dust and component degradation affect generation. Your own consumption may grow. DISCOM billing and net-metering rules evolve. For that reason the results are labelled as estimates throughout — we do not claim guaranteed savings, guaranteed payback or “100% accuracy”, and you should be sceptical of any calculator that does.

What the tool is genuinely good for is direction: understanding what size system your consumption justifies, what your roof can host, roughly what it should cost after subsidy, and how the payback math works. When you want site-specific numbers, book a free survey and the estimate becomes a proposal.