CAPEX vs OPEX vs Open Access Solar India: 2026 Comparison

TL;DR — CAPEX vs OPEX vs Open Access Solar Comparison

• CAPEX (you own it): Highest 25-year savings, fastest payback (3.0-4.5 years), full control. Requires upfront capital of ₹3.5-4.0 Cr per MW. Best for capital-rich corporates with high consumption.
• RESCO/OPEX (developer owns it on your roof): Zero capex, immediate 30-45% bill reduction via 25-year PPA at ₹4.50-5.50/kWh. Best for asset-light operators, REIT-held properties, multi-site chains.
• Open Access (off-site solar wheeled to you): Best for >1 MW load consumers, delivers landed cost of ₹3.20-3.85/kWh with 5-25 year PPA. Requires regulatory clearances and DISCOM cooperation.
• The right choice depends on: your capital availability, energy consumption scale, roof availability, risk appetite, and tax position. Most large Indian corporates use a hybrid stack — CAPEX rooftop + OPEX rooftop on additional buildings + Open Access for residual.
• A leading solar provider in India like Sun Wave Technologies structures all three models under one umbrella for industrial buyers with multi-state portfolios.

The bottom line: the answer to the right model depends on three variables — capital availability, on-site roof or land, and consumption scale. In short, the key insight is that the most cost-efficient outcome over 25 years is almost always a hybrid stack of CAPEX + OPEX + Open Access, not a single model. The main reason purists fail is they pick one model and miss the optimisation surface area; the result is leaving 15-25% of lifetime savings on the table.

The Three Models at a Glance

CAPEX Model: When You Own the Solar Plant

How It Works

Under the CAPEX model, you (the industrial buyer) commission a solar EPC company in India to build a solar plant on your roof or land. You pay the contract value upfront (₹3.5-4.0 Cr per MW), own the plant outright, claim accelerated depreciation tax benefits, and consume all the energy via net metering (up to state-defined caps).

Pros

• Lowest 25-year cost: LCOE of ₹2.40-2.80/kWh against grid HT-I of ₹7.50-9.50/kWh — nearly 70% savings.
• Full asset control: you own the plant, choose the EPC, set the maintenance schedule, decide on upgrades.
• Tax benefit: 40% Year-1 accelerated depreciation under Section 32(1)(iia) saves ₹35-40 lakh per MW for tax-paying corporates. See solar accelerated depreciation guide.
• Bankable asset: solar plant on balance sheet supports loans, can be securitised.
• Resale value: 7-15 years into the asset life, you can sell to RESCO operators at residual value if you exit.

Cons

• High upfront capital: ₹3.5-4.0 Cr per MW is a real capex commitment that may compete with other capex priorities.
• Operational risk: PR shortfalls, inverter failures, structural issues are your problem (mitigated by strong O&M contract with the EPC).
• Net metering caps: most states limit net metering to 1-2 MW per HT consumer. Larger plants need open access.

When CAPEX Is Right

• High monthly bills (₹15+ lakh/month).
• Tax-paying corporate with capacity to absorb the AD benefit.
• Strong balance sheet and lower-cost debt available (term loan at 8.5-9.5%).
• Long-term commitment to the site (20+ years expected).
• Sufficient roof or land area on-site.

For payback fundamentals see our solar panel ROI India guide.

RESCO/OPEX Model: When the Developer Owns the Solar Plant

How It Works

Under RESCO/OPEX, a developer (often Sun Wave Technologies as a developer arm separate from EPC) builds and owns the solar plant on your roof. You sign a 15-25 year Power Purchase Agreement (PPA) at a discounted tariff (₹4.50-5.50/kWh) and consume the energy. The developer carries all capex, performance risk, and O&M.

Pros

• Zero capex: no upfront cash outflow. The capex constraint is fully removed.
• Immediate savings: from Day 1, you pay 30-45% less than your grid tariff. No payback period.
• Performance risk on developer: PR shortfalls reduce the developer's revenue, not yours.
• Buy-out option: most PPAs have a buy-out clause from Year 7-10 — you can convert to ownership at residual value when capex becomes available.
• Pass-through documentation: simpler tax treatment for asset-light operators (cost is OPEX, fully expensed).
• Multi-site standardisation: a single developer manages all plants in your portfolio with consistent reporting.

Cons

• Higher per-kWh cost than CAPEX: ₹4.50-5.50/kWh PPA vs ₹2.40-2.80/kWh LCOE if you owned it. You pay the developer's IRR margin.
• Long-term commitment: 25-year PPAs with tariff escalation (1.5-2% YoY) lock you in.
• Roof access for developer: the developer needs unrestricted access to the roof for O&M and possibly upgrades.
• No AD tax benefit: the developer captures the 40% AD; you don't.
• Roof-life mismatch risk: if your roof needs replacement in Year 12 (when you've had the panels for 12 years), removal-and-reinstallation cost negotiation can be contentious.

When RESCO/OPEX Is Right

• Capital-constrained or capital allocated to core business.
• Asset-light operating model (REIT-held real estate, leased manufacturing facilities).
• Multi-site portfolio where standardisation matters more than per-site optimum.
• Risk-averse position where you prefer paying a known per-kWh rate over carrying performance risk.
• Hospitality, retail, IT parks, healthcare — segments where energy is not core to the business.

Open Access Model: When You Procure Off-Site Solar

How It Works

Under Open Access, you procure solar electricity from an off-site solar plant (typically 5-200 MW in a regional solar park) via the existing transmission and distribution grid. The structures are:

• Third-party open access: you sign a PPA with a private solar developer who supplies via the grid. Wheeling charges, transmission losses, and cross-subsidy surcharges apply.
• Group captive open access: you (and sometimes other consumers) hold 26%+ equity in the solar SPV that owns the plant. Group captive structures get wheeling and surcharge waivers in most states. See group captive solar India guide.
• Captive (single-buyer) open access: you alone hold 100% of the SPV and consume all the energy. Highest control, similar to CAPEX but off-site.

Pros

• Scale: 5-200 MW per offtake — much larger than rooftop net metering (1-2 MW).
• Off-site siting: no rooftop requirement; works for facilities with limited roof area (data centres, multi-storey commercial, urban offices).
• Best per-kWh in many states: landed cost of ₹3.20-3.85/kWh after wheeling and banking charges, with surcharge waivers for group captive in states like Tamil Nadu, AP, Telangana, Karnataka.
• Hourly matching: open access PPAs can be structured for time-block matching, supporting 24×7 carbon-free energy targets for hyperscalers.

Cons

• Regulatory complexity: open access NOC from DISCOM, scheduling and despatch coordination, REC accounting. Setup takes 6-12 months.
• Wheeling and banking charges: state-specific, ₹0.70-1.50/kWh, eroding 15-25% of arbitrage.
• Curtailment risk: DISCOM can curtail your scheduled energy during congestion. Mitigated by contractual liquidated damages but real.
• Cross-subsidy surcharge: only partly waived for group captive in many states. Full third-party open access pays full CSS.
• Equity capital: 26% group captive equity is ₹0.90-1.10 Cr per MW upfront — not zero capex.

When Open Access Is Right

• Consumption above 1 MW (the threshold for open access in most states).
• Insufficient on-site roof or land for the desired solar share.
• Need for >50% renewable share that on-site cannot deliver.
• Multi-state corporates wanting portfolio-level standardisation across many sites.
• ESG-driven 100% RE commitments (hyperscalers, large IT campuses, cement majors).

Hybrid Stack: The Right Strategy for Most Large Corporates

Most large Indian industrial corporates use a hybrid stack combining all three models:

For a typical Indian Tier-1 manufacturer with 50 MW connected load, the optimal stack is approximately:

• 3 MW CAPEX rooftop on flagship plant (₹10.5 Cr capex)
• 5 MW RESCO/OPEX rooftop on other 4 plants (zero capex)
• 15 MW captive ground-mount on land adjacent to flagship plant (₹52 Cr capex)
• 25 MW group captive open access from a regional solar park (₹22 Cr equity)
• 4 MWh BESS for time-shift (₹4.4 Cr capex)

Total renewable share: 50-55% of annual electricity. Total capex commitment: ₹89 Cr. Annual savings against pre-solar HT-I tariff: ₹38-45 Cr.

State-by-State Best Model

Maharashtra

Storage mandate applies for >100 kW. CAPEX dominant for new sites; RESCO with bundled BESS for asset-light. See Maharashtra storage mandate post.

Gujarat

CAPEX + Group Captive Open Access dominant. Khavda RE Park access. See Gujarat industrial guide.

Karnataka, Tamil Nadu, Andhra Pradesh, Telangana

Strong open access regimes. Hybrid CAPEX + Group Captive optimal. See Karnataka guide, TN guide, AP guide, Telangana guide.

Rajasthan

Solar park access excellent. Group Captive + CAPEX hybrid dominant. See Rajasthan industrial guide.

NCR (Haryana, UP, Delhi)

CAPEX + RESCO mix. UP's 2 MW net metering cap supports larger CAPEX. See Haryana industrial EPC guide, UP industrial guide, Faridabad-NCR guide.

Frequently Asked Questions

Which is cheaper over 25 years — CAPEX or OPEX?

CAPEX (you own the solar plant) is the cheapest over 25 years for a tax-paying corporate with available capital. The 25-year LCOE is ₹2.40-2.80/kWh against an OPEX PPA tariff of ₹4.50-5.50/kWh. For a 1 MW plant generating ~36,000 MWh over 25 years, CAPEX delivers ₹38-45 Cr lifetime savings vs ₹15-25 Cr for OPEX. The OPEX premium of ₹2.00-2.70/kWh is the developer's margin for carrying capex, performance, and operational risk.

When is OPEX/RESCO the right choice over CAPEX?

OPEX/RESCO is right when (1) capital is constrained or allocated to core business, (2) you operate asset-light (REIT real estate, leased facilities), (3) you have a multi-site portfolio where standardisation matters, (4) you prefer paying a known per-kWh rate over carrying performance risk, or (5) you cannot fully utilise the 40% accelerated depreciation tax benefit. Hospitality, retail, IT parks, and healthcare commonly choose OPEX.

Is Open Access cheaper than rooftop solar?

Open Access can be cheaper per kWh than rooftop CAPEX in states with strong cross-subsidy surcharge waivers (Tamil Nadu, Andhra Pradesh, Telangana) and abundant solar park supply. Group captive open access with 26%+ equity delivers landed cost of ₹3.20-3.85/kWh, comparable to or slightly better than rooftop CAPEX LCOE of ₹2.40-2.80/kWh after wheeling charges. For consumers above 1 MW load with limited rooftop area, open access is often the only path to >50% renewable share.

Can I combine CAPEX, OPEX, and Open Access?

Yes — most large Indian corporates use a hybrid stack. Typical combination: CAPEX rooftop on flagship sites + OPEX rooftop on remaining sites + group captive open access for residual renewable share above on-site capacity. This achieves 50-70% renewable share with mixed capex commitment, consistent with multi-stakeholder ESG and treasury constraints. Sun Wave Technologies structures all three models under a single umbrella for portfolio-level optimisation.

What's the right model for a multi-state factory chain?

For a multi-state factory chain (5+ plants across 3+ states), portfolio-level RESCO/OPEX with a single developer across all sites is typically optimal. Benefits: standardised SLD/BoM/EMS, consistent reporting (key for ESG disclosure), shared O&M routing economies, single PPA framework with site-specific schedules. For very large consumers (>10 MW load per site), augment with site-specific group captive open access for sites where ESG targets exceed on-site capacity. CAPEX is reserved for flagship sites with strong tax appetite and capital availability.

How does Maharashtra's storage mandate affect the choice?

Maharashtra's April 2026 storage mandate requires BESS for any new solar above 100 kW. Under CAPEX, you bear the BESS capex (₹50-65 lakh per MW for 500 kWh / 2-hour). Under OPEX, the developer bears it and prices into the PPA — Maharashtra OPEX tariffs are now ₹6.20-6.80/kWh (vs ₹4.80-5.40/kWh elsewhere), reflecting the bundled BESS. Under Open Access, mandatory BESS applies to new captive plants commissioned in Maharashtra; not to power wheeled from outside the state. See Maharashtra storage mandate post.

What's the typical contract tenor for each model?

CAPEX: you own the asset; no PPA (just an EPC contract for ~6-12 months of construction + 5-25 year O&M agreement). OPEX/RESCO: 15-25 year PPA with 1.5-2% annual tariff escalation, buy-out option from Year 7-10. Open Access: 5-25 year PPA with the SPV (group captive) or with the developer (third-party). Most CFOs prefer 25-year tenors to lock in long-duration savings; some prefer 15-year tenors for capital flexibility.

Sources

• MNRE Renewable Energy Policy Updates (multi-state)
• IndianPSEB / SERC Tariff Orders FY 2026-27
• India installs record 45 GW solar capacity in FY2026 — pv magazine India