How to Calculate ROI on a 1MW Solar Plant in India

A 1 MW ground-mount solar plant is one of the most common entry points for large individual investors, family offices, and mid-market corporates entering India's clean energy space. At current benchmark costs, the total capital outlay is ₹3.5–₹4.5 crore depending on state, module type, and EPC quality. Done right, the same plant delivers a levered IRR of 14–18% over a 25-year life. Here is how to build that number from first principles.

Step 1 — Establish your capital cost (CAPEX)

The EPC cost benchmark for a 1 MW ground-mount plant with ALMM-compliant mono-PERC or TOPCon modules is currently ₹3.60–₹4.20 crore (all-in, including civil, electrical, SCADA, and grid connectivity up to 1 km). Key variables:

• Module type: TOPCon adds ₹8–₹12 lakh over mono-PERC but reduces BOS costs per Wp because fewer panels are needed for the same output.
• Grid connection: Sites requiring HT line extension beyond 1 km add ₹6–₹15 lakh depending on terrain.
• Land premium: If purchasing vs. leasing land for 25 years, factor in the full land cost or capitalise the lease at ₹15,000–₹40,000/acre/year depending on state.
• Contingency: Budget 5% of EPC as a contingency reserve for commissioning overruns.

Step 2 — Estimate annual generation (P50)

Generation is driven by irradiance, tilt, shading losses, and panel degradation. A 1 MW plant in:

These are P50 estimates assuming single-axis fixed-tilt. Single-axis trackers add 12–18% generation at an incremental cost of ₹18–₹25 lakh per MW. Apply a 0.5% annual degradation rate to generation from Year 2 onwards in your model.

Step 3 — Project annual revenue

Revenue = Generation (MU) × Tariff (₹/unit). The tariff depends on your off-take structure:

• PPA with a C&I buyer: ₹3.80–₹5.20/unit depending on state, load factor, and CSS position. Escalation clauses of 1–3% annually are common.
• Group Captive supply: ₹3.50–₹4.50/unit (CSS exemption partially offsets lower headline tariff).
• Merchant sale / exchange: Variable — IEX day-ahead prices have ranged ₹2.80–₹6.50/unit in FY2025. Higher upside, higher risk.
• State DISCOM PPA (REWA/SECI-type): ₹2.50–₹3.00/unit — lower tariff but sovereign off-take risk.

For a worked example, assume a Rajasthan C&I PPA at ₹4.20/unit with 2% annual escalation, generating 1.90 MU in Year 1. Year 1 revenue ≈ ₹79.8 lakhs.

Step 4 — Model operating costs (OPEX)

Annual OPEX for a 1 MW plant typically runs ₹6–₹9 lakh/year, covering O&M (cleaning, preventive maintenance, inverter service), insurance, land lease if applicable, and SLDC/metering fees. Assume 3–4% annual OPEX escalation. By Year 15, annual OPEX is ₹10–₹14 lakh.

Step 5 — Calculate IRR and payback

Using the Rajasthan C&I PPA example above (CAPEX ₹4.00 crore, Year 1 revenue ₹79.8 lakh, OPEX ₹7.5 lakh, no debt):

• Simple payback: ₹4.00 Cr ÷ ₹72.3 lakh net Year 1 cash flow = 5.5 years
• Equity IRR (25-year, unlevered): ~15.8%
• NPV at 12% discount rate: ~₹2.2 crore positive

Adding 50% debt at 9% per annum improves equity IRR to 18–20% because the after-tax cost of debt is well below the project's cash yield. This is why most institutional investors in India use project finance for solar — it is capital-efficient, not because the equity is weak.

The four variables that matter most

1. Tariff level and escalation clause — a 50 paise/unit difference compounds to a ₹50–₹60 lakh NPV swing over 25 years.
2. CUF / generation output — a 1% higher CUF adds roughly ₹3–₹4 lakh in annual revenue on a 1 MW plant.
3. CAPEX per Wp — every ₹5 lakh saved on EPC goes directly into equity IRR. Vetting module quality and contractor track record pays disproportionate dividends here.
4. Off-take counterparty risk — a discounted tariff with a strong industrial buyer often outperforms a higher merchant tariff over the full PPA life.