Solar for Factories & Manufacturing Units in India: Cost, Savings & ROI (2026)

A practical, numbers-first guide for factory owners, plant heads and finance teams evaluating rooftop and captive solar in 2026. By Solnce Energy.

Electricity is one of the few large line items in a manufacturing P&L that a plant head can structurally reduce without touching headcount, raw material or process yield. Solar for factory operations works in India for a simple reason: industrial consumers pay among the highest tariffs in the country, and a factory shed offers exactly the kind of large, unobstructed, shadow-free roof that solar needs. This guide sets out what an industrial solar plant costs in 2026, what it generates, what it saves, and how the tax and regulatory position has changed this year.

Why Industrial Power Costs Make Solar Compelling

Factories rarely pay a single headline rate. An HT industrial bill is a stack, and solar interacts with each layer differently.

The HT tariff stack

• Energy charge — the per-unit rate. Across major industrial states, published HT industrial rates in 2026 sit broadly in the ₹7–₹9.50 per unit band before duties; sources vary and every State Commission issues its own annual tariff order.

• Demand charges — billed on contract or recorded maximum demand in kVA, payable whether or not you draw. A grid-tied solar plant without storage does not reliably reduce your sanctioned demand, though it can shave recorded maximum demand if your peak reliably falls in solar hours.

• Electricity duty, fuel surcharge and cess — these ride on consumption, so every unit solar displaces removes the duty on that unit too.

• Power factor and load factor incentives or penalties — solar inverters can be configured to support reactive power management, but this needs to be designed in rather than assumed.

Time of Day (ToD) and the solar-hours question

ToD tariffs are now widely applied to commercial and industrial consumers above 10 kW. Under the Electricity (Rights of Consumers) Rules framework, the peak-period tariff for C&I consumers is set at not less than 1.20 times the normal tariff, while the tariff during the eight solar hours specified by the State Commission is at least 20% below normal. Several state orders go further, with off-peak rebates and peak surcharges of 25%–30%.

The honest implication: solar output arrives during the discounted ToD window, so a displaced solar-hour unit is worth somewhat less than your average blended rate. We therefore model industrial savings on a displaced value of roughly ₹7.50–₹8.50 per unit rather than on the highest number on the bill.

How Much Roof Does a Factory Actually Have?

Area per kW depends far more on roof geometry than on panel brand. On a pitched sheet-metal shed, modules are mounted flush to the slope with no inter-row shading gap, so the plant packs tighter. On a flat RCC roof, tilted rows need pitch spacing to avoid self-shading, which costs area.

• Pitched sheet-metal roof, flush-mounted: roughly 65–85 sq ft per kW (indicative).

• Flat RCC roof, tilted rows: roughly 90–110 sq ft per kW (indicative). Many published guides quote a flat rule of thumb of 100 sq ft per kW; sources vary.

In practice, a 50,000 sq ft usable shed roof typically supports 500–750 kW, before deductions for skylights, turbo-ventilators, ducting, exhaust stacks, walkways and fire-tender access — a realistic survey usually removes 10%–25% of gross roof area.

Table 1: Rooftop suitability by roof type

Mounting on Sheet-Metal and Asbestos Roofs

Structural design is where industrial rooftop projects are won or lost. Three points matter most.

• Wind load governs, not dead load. Mounting structures must be designed to IS 875 (Part 3), with design wind pressure derived from the site basic wind speed and the relevant terrain, height and topography factors. Coastal and high-wind zones need heavier sections and tighter clamp spacing. The added dead load itself is modest — indicatively 10–15 kg per sq m for a flush sheet-roof system and 15–25 kg per sq m for tilted structures on flat roofs — but uplift is the design case.

• Load path, not sheet strength. On any sheet roof, the mounting system should transfer load into purlins, rafters or trusses, never into the cladding sheet alone. A structural review of the existing shed is a legitimate scope item and should be quoted, not skipped.

• Asbestos needs a decision, not a workaround. AC sheets are brittle, cannot bear foot traffic and are often decades old. The defensible options are to replace the affected bays with pre-coated sheet before installation, or to build an elevated structure that spans onto the trusses. Asbestos-containing material is a regulated waste stream in India; removal and disposal must follow the applicable hazardous waste rules and your State Pollution Control Board's requirements. Treat any contractor who proposes drilling straight into live AC sheet as a red flag.

Roof age is the other silent variable. If the shed roof has fewer than eight to ten years of remaining life, it is usually cheaper to re-sheet first than to dismantle and re-install a solar array later.

Cost, Generation, Savings and Payback by System Size

The table below uses a generation assumption of 1,400–1,500 units per kW per year (the national range is roughly 1,100–1,800 depending on latitude, soiling and shading) and a displaced grid value of ₹7.50–₹8.50 per unit. All figures are indicative and assume high self-consumption. Larger plants generally achieve a lower per-kW cost.

Table 2: Indicative cost, generation, savings and payback

What actually moves the IRR

• Self-consumption ratio — the single biggest lever. Every exported or curtailed unit is worth far less than a self-consumed one.

• Tariff escalation — most models assume 3%–5% a year. Higher escalation shortens payback materially over 25 years.

• Degradation and O&M — assume roughly 0.5% output loss a year and 1%–1.5% of capex a year for O&M, cleaning, insurance and monitoring.

• Financing structure — a debt-funded plant changes equity IRR sharply in either direction depending on interest rate and tenor.

Accelerated Depreciation and GST Input Credit

Accelerated depreciation under the Income-tax Act, 2025

The Income-tax Act, 2025 came into force on 1 April 2026 and re-enacts depreciation under Section 34 (formerly Section 32 of the Income-tax Act, 1961). The rate for renewable energy devices is unchanged at 40% in Year 1 on the written-down value method, halved to 20% where the asset is put to use for less than 180 days in the year. Commissioning before the end of September therefore matters for the first-year claim.

What this is worth: on a ₹2.00 crore plant, a 40% first-year claim is a ₹80 lakh deduction. At an effective corporate rate of about 25.17% under the concessional regime, that is roughly ₹20 lakh of tax deferred in Year 1 — around 10% of capex. Depreciation is a timing benefit, not a permanent one, but it meaningfully improves early cash flow and typically pulls simple payback in by four to six months. Your actual rate depends on the tax regime your company has elected; take advice.

GST position in 2026

The 56th GST Council reduced renewable energy devices from 12% to 5%, effective 22 September 2025. For a turnkey EPC contract assessed on the 70:30 works-contract valuation, the blended rate is 8.9% — that is 0.7 x 5% plus 0.3 x 18%. Many pages published during 2026 still quote the old 12% and 13.8% figures; those are out of date.

On input tax credit, multiple Authority for Advance Ruling decisions have held that a rooftop plant bolted to a building and used for captive consumption qualifies as plant and machinery, so ITC is available. Two conditions recur: capitalise the asset under plant and machinery rather than building or civil works, and use the output for taxable business supply. Where power is exported and sold as exempt supply, credit can be restricted or reversed. AAR rulings bind only the applicant, so confirm your position with your tax adviser.

Three Routes: Net Metering, Captive and Open Access

Net metering in India is permitted up to 500 kW or the sanctioned load, whichever is lower. (The widely republished "10 kW cap" comes from a 2020 draft that was withdrawn and should be disregarded.) For a factory wanting more than 500 kW, this is the fork in the road: either run the larger plant behind the meter on a zero-export or net-billing basis, or move to a captive or open-access structure.

Table 3: Route comparison for industrial consumers

Rooftop and off-site are not mutually exclusive. A common pattern is to fill the roof first, because on-site generation faces no wheeling or surcharge exposure, and then contract open access or group captive for the balance of the load.

Self-Consumption: Why Day-Shift Factories Win

Solar generates between roughly 7 a.m. and 6 p.m., peaking near midday. The closer your production curve sits to that shape, the better the economics.

• Single day shift (9 a.m. to 6 p.m.): the best fit. Self-consumption of 85%–95% is realistic if the plant is sized to daytime load rather than to total consumption.

• Two or three shifts / continuous process: effectively 100% of solar output is absorbed, but solar covers a smaller share of total consumption, so the percentage saving on the bill is lower even though the plant performs well.

• Weekly off days: a Sunday shutdown puts about 14% of annual generation at risk. With net metering it is banked; on a zero-export connection it is lost. Model this explicitly.

• Seasonal and annual shutdowns: a two-week maintenance shutdown removes roughly 4% of annual generation from self-consumption.

• Sizing discipline: a widely used rule of thumb is to size the plant to about 70%–80% of average daytime demand. Oversizing on a zero-export connection is the fastest way to turn a four-year payback into a seven-year one.

Unit Economics, ESG and Buyer Compliance

For energy-intensive manufacturing, power can be 8%–25% of conversion cost. Shifting even a third of daytime consumption to a self-owned asset with near-zero marginal cost changes the per-unit cost of production for 25 years, and it does so predictably — a solar plant has no fuel escalation.

There is a second, increasingly commercial reason. The EU Carbon Border Adjustment Mechanism entered its definitive phase in January 2026, with verified embedded-emissions reporting now required for covered goods including steel, aluminium and cement. Renewable electricity, properly documented, can reduce the electricity-related emissions attributed to production, and exporters reporting verified actual data generally fare better than those defaulted to country default values. Separately, RE100 members and large OEMs increasingly push renewable-energy expectations down their supply chains, and on-site solar is the simplest evidence a Tier-1 or Tier-2 supplier can produce in a customer sustainability audit.

Compliance watch-list — dated July 2026

• ALMM: the List-II mandate covering solar cells applies from 1 June 2026. MNRE has extended the exemption for net-metering and open-access projects to 31 December 2026. This area is moving quickly — confirm the position applicable on your order date.

• Draft Electricity (Rights of Consumers) Amendment Rules, 2026: issued 12 March 2026 with proposed effect from 1 October 2026, these may require prosumers above 500 kW to install battery energy storage. This is still a draft and has not been notified; treat it as a planning risk, not a present obligation.

• PM Surya Ghar: residential only. It does not cover commercial or industrial installations, and no central capital subsidy of that kind is available to a factory.

Frequently Asked Questions (FAQs)

1. Is my factory eligible for the PM Surya Ghar subsidy?

No. PM Surya Ghar is a residential rooftop scheme only. Commercial and industrial systems are not covered. Industrial projects rely instead on accelerated depreciation, GST input credit and the underlying tariff saving, which for HT consumers is usually a stronger financial case than a residential subsidy would be.

2. How much does a 500 kW factory solar plant cost in 2026?

Indicatively ₹2.05–₹2.55 crore turnkey, based on a range of roughly ₹41,000–₹51,000 per kW. Published market figures for C&I rooftop span ₹35,000–₹60,000 per kW, so sources vary. Roof type, structure height, module and inverter grade, cable runs and evacuation distance are the main swing factors.

3. What payback period should a factory expect?

Typically about three to five years on a simple basis for a well-sited plant with high self-consumption, before tax effects. Accelerated depreciation usually pulls that in by a further four to six months. Poor self-consumption, low tariffs or heavy shading can push payback beyond six years.

4. What IRR do industrial solar projects deliver?

Project IRR over a 25-year life is commonly modelled in the 15%–25% range, and the number is highly sensitive to assumptions on tariff escalation, self-consumption and O&M. Treat any single headline IRR with caution unless the underlying assumptions are disclosed.

5. How much roof area does a factory solar plant need?

Roughly 65–85 sq ft per kW on a flush-mounted pitched sheet roof and roughly 90–110 sq ft per kW on a flat RCC roof with tilted rows. A 250 kW plant therefore needs somewhere around 16,000–25,000 sq ft of clear, shadow-free roof after deducting skylights, ventilators and walkways.

6. Can solar be installed on an asbestos cement sheet roof?

It requires specialist assessment rather than a standard quote. AC sheets are brittle, non-walkable and frequently past design life. The safer approaches are to replace affected bays with pre-coated sheet before installation, or to use an elevated structure that transfers all load to the purlins and trusses. Asbestos waste handling and disposal are regulated — check requirements with your State Pollution Control Board.

7. Will solar reduce my contract demand or demand charges?

Not reliably. A grid-tied plant without storage does not reduce your sanctioned or contract demand, and demand charges remain payable. It can reduce recorded maximum demand where your peak consistently occurs during solar hours, but this must be verified against your actual half-hourly demand data, not assumed.

8. What GST applies to a turnkey factory solar plant in 2026?

The 56th GST Council reduced renewable energy devices from 12% to 5% with effect from 22 September 2025. Under the 70:30 works-contract valuation used for turnkey EPC, the blended rate is 8.9% (0.7 x 5% plus 0.3 x 18%). Pages still quoting 12% or a 13.8% blended rate are using the pre-September 2025 position.

9. Can my company claim GST input tax credit on the plant?

Where the plant is used for captive consumption in a taxable business, several AAR rulings have held that it qualifies as plant and machinery and ITC is available. Capitalise it under plant and machinery, not building or civil works. If output is sold as exempt supply, credit may be restricted or reversed. AAR rulings bind only the applicant, so confirm with your tax adviser.

10. How much is accelerated depreciation worth?

Depreciation is now governed by Section 34 of the Income-tax Act, 2025, which came into force on 1 April 2026 and re-enacts what was Section 32 of the 1961 Act. The rate for renewable energy devices remains 40% in Year 1 on the WDV method. On a ₹2 crore plant that is an ₹80 lakh deduction, worth roughly ₹20 lakh of tax deferred at a 25.17% effective rate.

11. Does it matter when in the year we commission?

Yes. If the asset is put to use for less than 180 days in the financial year, the Year-1 depreciation rate is halved to 20%. Commissioning on or before roughly the end of September preserves the full 40% first-year claim.

12. What is the net metering limit for an industrial consumer?

Net metering is permitted up to 500 kW or the sanctioned load, whichever is lower. The frequently republished "10 kW cap" originates from a 2020 draft that was withdrawn and does not represent the current position. State implementation and settlement rules still differ, so check your DISCOM's applicable regulations.

13. My factory runs a single day shift — is solar still worth it?

A day-shift factory is close to the ideal profile, because generation and consumption overlap almost completely. Self-consumption of 85%–95% is realistic when the plant is sized to daytime load rather than total annual consumption.

14. What happens on Sundays and during the annual shutdown?

A weekly off day puts roughly 14% of annual generation at risk, and a two-week annual shutdown a further 4% or so. With net metering those units are banked and settled under state rules. On a zero-export connection they are simply not produced. Model shutdown patterns before sizing.

15. Does a three-shift continuous plant benefit from solar?

Yes, and it achieves near-total self-consumption because there is always load to absorb the output. The difference is that solar covers a smaller share of total consumption, so the percentage reduction in the electricity bill is lower even though the plant itself performs very well.

16. When does group captive or open access beat a rooftop plant?

When your load is far larger than your roof can serve. Group captive requires the consumer group to hold at least 26% equity and consume at least 51% of the output, in return for exemption from cross-subsidy and additional surcharge — charges that can otherwise add roughly ₹1.50–₹2.90 per unit to a third-party PPA. Most factories fill the roof first and contract off-site power for the balance.

17. Does ALMM apply to my factory project?

As at July 2026, the ALMM List-II mandate covering solar cells applies from 1 June 2026, while MNRE has extended the exemption for net-metering and open-access projects to 31 December 2026. This position has changed several times, so confirm the rule applicable on your order and commissioning dates before finalising module procurement.

18. Will I need a battery?

Not for a conventional day-shift self-consumption project in 2026. However, the draft Electricity (Rights of Consumers) Amendment Rules, 2026, issued on 12 March 2026 with proposed effect from 1 October 2026, may require prosumers above 500 kW to install battery storage. These rules remain in draft and are not yet notified, so treat storage as a planning contingency rather than a current requirement.

19. Will solar damage my roof or void the sheet warranty?

A properly engineered system should not. Non-penetrative clamp systems on standing-seam and ribbed profiles avoid new holes entirely; where penetration is unavoidable, sealed fasteners with EPDM washers are used. Involve your roofing supplier early if a sheet warranty is still live, and re-sheet worn bays before installation rather than after.

20. Does solar help with CBAM, RE100 or customer ESG audits?

It can. The EU CBAM entered its definitive phase in January 2026 and now requires verified embedded-emissions data for covered goods, where renewable electricity with appropriate documentation can reduce attributed electricity emissions. For RE100 members and large OEM customers, an on-site solar plant with metered generation data is among the simplest pieces of evidence a supplier can present. Specific CBAM treatment depends on the product, the reporting methodology and verification requirements — take specialist advice.