Solar CAPEX vs OPEX RESCO PPA in India: complete financial model tax shields and true long-term returns

CAPEX gives an industrial solar buyer asset ownership, eligible depreciation deductions and the full avoided-electricity benefit, alongside operating responsibility. A RESCO PPA substitutes developer-funded electricity purchases for plant investment but introduces long-term contractual obligations. This Bearworx guide compares both routes through an illustrative 25-year financial model, separating genuine cash savings from tax assumptions, accounting classifications and tariff-pitch arithmetic.

What is the financial difference between CAPEX and OPEX solar?

Under CAPEX, the industrial entity purchases and owns the solar asset using equity, bank borrowing or both. It capitalises eligible expenditure, claims available tax depreciation and retains 100% of the avoided-grid-purchase benefit before operating costs, financing and taxes. Ownership also leaves it bearing residual generation and O&M performance risk, even where contractors provide maintenance or guarantees under statutory income tax guidelines.

Under OPEX/RESCO, a third-party independent power producer or developer funds, owns and maintains the rooftop plant. The industrial entity purchases generated electricity under a long-term power purchase agreement; this guide considers 15–25-year contracts and models 25 years. Asset ownership remains with the developer unless contractual transfer provisions apply.

For industrial solar leasing vs asset ownership, distinguish a power purchase from an equipment lease. Their contractual rights and accounting consequences need not match. Calling expenditure “OPEX” does not establish off-balance-sheet treatment under corporate reporting guidelines issued by the Ministry of Corporate Affairs (MCA).

The CFO Decision Matrix

This matrix separates equity-funded ownership from bank-financed ownership; both are CAPEX procurement. RESCO accounting remains subject to contract assessment under Indian accounting standards.

Use the matrix to identify constraints before comparing quotations. A low upfront payment is a liquidity advantage, not proof of higher lifetime value.

How does solar accelerated depreciation under Section 32 affect returns?

The familiar solar accelerated depreciation Section 32 framework allows eligible owners to deduct depreciation from taxable business income. The prescribed solar-system rate is 40% on written down value, not a 40% cash subsidy. Each subsequent deduction applies to the remaining eligible tax block value.

Important date correction: the Income Tax Act, 2025, took effect on April 1, 2026. Depreciation now appears in Section 33 and the former Section 115BAA corporate regime in Section 200. This guide retains the familiar legacy labels for comparison; verify statutory cutovers directly through the official Income Tax Department of India.

Corporate tax rates and the Year-1 shield

The Section 115BAA regime combines 22% base tax, 10% surcharge and 4% cess: 25.168%, conventionally rounded to 25.17%. Ordinary prescribed depreciation remains available; additional depreciation is excluded. Legacy companies taxed at a 30% base face approximately 31.2%–34.94%, depending on surcharge; some domestic companies qualify for a lower 25% base, so that range is not universal.

For an illustrative 500 kW system costing ₹2.0 crore, assuming the entire amount qualifies for 40% depreciation and full-year eligibility:

• Deduction: ₹200 lakh × 40% = ₹80 lakh.

• Cash-tax reduction: ₹80 lakh × 25.168% = ₹20.1344 lakh, rounded to ₹20.13 lakh.

• Remaining WDV: ₹120 lakh, before other block adjustments.

Using rounded 25.17% instead produces ₹20.136 lakh, which rounds to ₹20.14 lakh. The ₹20.13 lakh result therefore requires the unrounded statutory rate. This is potential current-year tax relief, not instant liquidity recovery on commissioning; realisation depends on taxable income and tax-payment timing. Assets acquired and put to commercial use for fewer than 180 days in the financial year generally receive half the prescribed first-year rate (20% WDV).

Zero immediate shield is not universal ineligibility

Model the buyer’s actual cash-tax position rather than multiplying depreciation by a headline rate:

• Exempt trust-run universities: there may be no corporate cash tax to reduce. Separate charitable-tax rules also restrict duplicate depreciation where acquisition was treated as the application of income.

• Loss-making companies: immediate tax relief can be zero, although unabsorbed depreciation may retain future value subject to applicable rules.

• MAT-paying companies: depreciation may not reduce current cash tax while MAT remains binding. That does not automatically eliminate depreciation eligibility or all future tax value.

kVAh Billing / Marginal Tariff

The blended bill fallacy compares an illustrative ₹4.50/unit PPA against an ₹8.50 average grid bill as though every bill component disappears. Instead, calculate the marginal daytime charge actually avoided. Do not count demand charges, minimum charges or other components unless the applicable billing mechanism demonstrably reduces them.

Review our complete engineering study on kVAh billing reality and solar power factor correction before converting daytime generation into bankable savings.

The rooftop solar PPA escalation clause

For ₹4.50/unit with 3% annual escalation, the tariff in operating year t is ₹4.50 × 1.03^(t−1). The first increase occurs in Year 2:

Thus, it does not cross ₹6 in Year 10 or reach ₹9.14 in Year 24 under this convention. If daytime DISCOM charges remain frozen, the contractual escalation progressively narrows—and can reverse—the saving. Require fixed-grid-tariff and declining-daytime-tariff sensitivities, not an assumed perpetual grid-price increase.

Ind AS 116 and balance-sheet recognition

For an Ind AS reporting entity, assess whether the agreement conveys control over an identified asset: substantially all economic benefits plus the right to direct its use. Merely buying output does not settle that assessment. The official accounting framework is governed by Indian Accounting Standard (Ind AS) 116 issued by the Institute of Chartered Accountants of India (ICAI).

Where lease accounting applies, recognise a Right-of-Use asset and corresponding lease liability based on qualifying payments. Do not automatically capitalise every forecast PPA payment: genuinely output-dependent variable payments are generally excluded from initial liability measurement unless otherwise qualifying. Recognition can affect leverage, EBITDA presentation and covenant calculations; obtain your statutory auditor’s written assessment before promising off-balance-sheet procurement.

A reproducible solar CAPEX vs OPEX financial model

The following is an illustrative scenario, not a quotation or performance forecast. Both routes use identical generation and avoided-grid assumptions; differences arise from ownership costs, tax depreciation and PPA payments.

Model assumptions and formulas

• Plant: 500 kWp, generating 750,000 kWh in Year 1, degrading 0.6% annually.

• All generation is self-consumed; avoided daytime grid tariff stays ₹8.00/kWh.

• CAPEX: ₹200 lakh, entirely equity-funded; illustrative O&M ₹2 lakh annually, held constant.

• RESCO: zero initial investment; ₹4.50/kWh, escalating 3% annually; developer bears modelled O&M.

• Tax: 25.168%, sufficient taxable profits, full first-year depreciation and immediate annual utilisation.

• Cash flows occur at year-end; discount rate is 10%. No subsidy, residual value, debt, deposits, replacement expenditure or indirect-tax effects are included.

• To verify whether your system capital costs align with market pricing for Tier-1 modules, string inverters, and galvanised structures, review our commercial solar cost per kW and unbundled BOQ breakdown.

For year t, generation is 750,000 × 0.994^(t−1). Let G be avoided grid expenditure, M owner operating costs and P PPA payments:

CAPEX cash flow = (G − M) × 0.74832 + tax depreciation × 0.25168.

RESCO cash flow = (G − P) × 0.74832.

These formulas tax the reduced electricity expense consistently. Adding depreciation relief to untaxed electricity savings would overstate CAPEX returns.

25-Year Financial Comparison

All monetary figures below are ₹ lakh, rounded. Annual rows show after-tax incremental cash flow against continuing grid purchases; CAPEX cumulative net benefit deducts the initial investment.

IRR measures the return on invested equity; it cannot fairly rank a zero-investment PPA. Compare incremental NPV and liquidity instead. Constant O&M and omitted replacements favour CAPEX, so replace these simplifying assumptions with lifecycle quotations before approving investment.

For bank financing, add debt drawdown, interest, principal repayments, fees and applicable interest tax effects. Recalculate equity IRR separately from project returns; leverage changes both risk and equity cash flows.

Engineering and approvals that change financial returns

Net Metering vs Zero Export

Underwrite usable generation rather than assuming every generated unit offsets retail purchases. Confirm export settlement and permissions against current state rules; review our technical blueprint on behind-the-meter captive solar approvals and zero export as an operational starting point.

Structural / PEB Roof

Require an engineer’s review of roof capacity, purlin connections, wind uplift, and remaining roof life. Include our technical checklist on PEB shed structural load limits and IS 875 wind derivations in that diligence scope.

High-Voltage Interconnection

Obtain a site-specific scope for protection, metering, transformers, cabling, and shutdown work. Review our technical guide on 11 kV vs 33 kV solar grid interconnection before accepting either an EPC boundary or PPA developer exclusions.

For a procurement-ready comparison, have Bearworx audit your 15-minute interval demand data, balance sheet tax capacity, and structural drawings through our turnkey commercial and industrial solar engineering solutions. We design and build high-yield captive solar infrastructure engineered for long-term internal rates of return.

FAQs

Q1.Should a RESCO proposal receive an infinite ROI?

No. Zero initial investment makes conventional investment-return ratios unsuitable; use discounted incremental cash benefit.

Q2.How should refundable security deposits be modelled?

Record the initial cash outflow and expected repayment separately, including timing and counterparty risk.

Q3.Should an end-of-term asset transfer receive automatic value?

No. Include only a defensible value after transfer costs, remaining useful life and contractual conditions.

Q4.How should termination compensation enter the comparison?

Add it to the relevant exit scenario rather than hiding it within an uninterrupted 25-year forecast.

Q5.What should the downside debt case test?

Test whether reduced generation and usable savings still cover scheduled debt service without assuming refinancing.

For a procurement-ready comparison, ask Bearworx to reconcile interval consumption, tax capacity, engineering scope and contract obligations through turnkey commercial and industrial solar engineering solutions. Choose the route with defensible after-tax value and acceptable downside exposure—not simply the lowest opening tariff.