OPEX

What is OPEX

OPEX, Operating Expenditure, is the recurring cost of running a solar plant over its operational life. It includes preventive and corrective maintenance, module and array cleaning, monitoring, insurance, security, land lease (for utility), property tax, spare parts, and replacement of consumable components.

OPEX is one of two cost categories in solar lifecycle economics, alongside CAPEX. While CAPEX dominates the cost structure of solar (the larger share of lifecycle cost for most plants), OPEX directly affects net cash flow and LCOE. Lower OPEX means more revenue retained per kWh sold. Buyers weighing the two models in detail can compare them in the CAPEX vs OPEX decision guide for C&I buyers.

For Indian solar, OPEX depends on plant size, location, dust load and contract scope. Utility plants add land lease and security; residential rooftop OPEX is often bundled into an AMC package. Use quotes for the specific site rather than a generic range.

OPEX explained simply

After you build a solar plant, you have to keep it running. Cleaning the panels regularly, fixing breakdowns, paying insurance, paying property tax. These costs continue every year for 25 years. The total is the OPEX.

OPEX is smaller than CAPEX but matters because it eats into revenue every year.

Why OPEX matters

LCOE input. Lower OPEX directly reduces LCOE.

Project finance. Lenders model OPEX in cash flow projections.

PPA economics. Net revenue = PPA revenue minus OPEX.

Plant performance. Inadequate OPEX leads to declining output and revenue.

Long-term contracts. RESCO PPAs require committed OPEX over 25 years, a structure explained in detail in Zero Cost Solar India, RESCO and OPEX Models Explained.

Customer expectation. Residential customers often expect “set and forget” OPEX, leading to disappointed yield.

Components of OPEX

The main line items are preventive maintenance and cleaning, corrective maintenance and spares, monitoring and SCADA, insurance, land lease (utility plants), property tax, security (utility plants) and statutory dues and audits. Their shares vary by site and contract, so take them from the O&M quotes and insurance premiums for your project.

Technical deep dive

Indian solar OPEX benchmarks

CERC’s Renewable Energy Tariff Regulations, 2024, Regulation 48, provide that the Commission “shall determine only project specific O&M expenses considering the prevailing market trends” (as reproduced in CERC order in Petition No. 175/GT/2024, 20 March 2025). There is no fixed ₹ per MW norm for solar PV, so a per-MW benchmark table is not given here. Collect O&M offers for the site and compare them against each other.

OPEX escalation

OPEX is usually escalated each year in line with inflation. Some PPAs include automatic CPI escalation; others are flat with periodic review.

OPEX vs revenue

Developers modelling this trade-off across a portfolio typically run it through a dedicated solar financial modelling tool rather than a spreadsheet, since OPEX escalation compounds differently from revenue escalation over 25 years.

Cleaning frequency in Indian conditions

Cleaning frequency follows dust load, rainfall and local pollution, so dry, dusty and industrial sites need more frequent cleaning than wetter ones. Set the minimum cycle in the O&M contract and adjust it using soiling measurements (see soiling) rather than a fixed regional schedule.

Real-world applications

PPA financial modelling.

LCOE calculation.

O&M contract benchmarking.

Insurance premium negotiation.

State SERC tariff order O&M assumptions.

Residential AMC pricing.

Advantages of disciplined OPEX

Sustained plant performance over 25 years.

Maximised energy output.

Lower equipment failure risk.

Better insurance terms.

Compliance with PPA performance guarantees.

Limitations

Recurring drag on cash flow.

Escalation risk over 25 years.

Quality compromises in cost-driven O&M lead to underperformance.

Cleaning labour availability varies by region.

Common problems

Inadequate cleaning frequency reducing PR.

Inverter fan failures from skipped preventive maintenance.

DC connector corrosion in coastal sites.

Vegetation overgrowth in ground-mount sites.

Soiling sensor not maintained, hiding cleaning need.

Security incidents at remote utility sites.

Bird damage to wiring.

Best practices

Specify minimum cleaning frequency in O&M contracts.

Use IEC 61724 monitoring standard.

Maintain spares inventory on site for critical items.

Budget for component replacement (fans at year 5 to 7, capacitors at year 8 to 12).

Audit OPEX against budget quarterly.

Insure adequately for natural disasters.

Track soiling losses against cleaning ROI.

Comparison: OPEX components across project types

Indian market context

CERC’s Renewable Energy Tariff Regulations, 2024 (Regulation 48) leave solar PV O&M to be determined project by project, not as a fixed benchmark.

State SERC tariff orders reference O&M costs in feed-in tariff setting.

Major O&M operators in Indian solar include Tata Power Solar, Mahindra Susten, Sterling and Wilson, Larsen and Toubro, ReNew O&M and various specialised firms, alongside full-service solar EPC providers that bundle O&M into turnkey contracts.

PM Surya Ghar mandates 5-year comprehensive maintenance bundled with installation.

RESCO PPAs include developer-borne O&M for the contract duration.

Standards and certifications

Common mistakes

Underbudgeting OPEX in initial financial models.

Skipping preventive maintenance to save cost short-term.

Inadequate cleaning frequency.

Choosing cheapest O&M operator without performance track record.

Skipping insurance.

Not maintaining critical spares inventory.

Treating monitoring as optional.

Key takeaways

OPEX is the recurring cost of running a solar plant over 25 years. CERC’s 2024 renewable tariff rules assess solar PV O&M project by project, so budget from real O&M quotes for the site. Cleaning, preventive maintenance and insurance are the main recurring items. Disciplined OPEX sustains performance and protects PPA economics. Underbudgeting OPEX is the most common path to a stretched payback period and disappointed yield.

Need solar plant O&M contracts that work?

O&M contracts are normally signed with the EPC that built the plant or a specialist O&M operator. Qbits Energy makes solar inverters; for inverter service support, see the authorised service partner network.

Further reading

For how OPEX plays out in real projects, these guides go deeper:

• Solar CAPEX vs OPEX: The C&I Buyer Decision Guide
• Zero Cost Solar India: RESCO & OPEX Models
• Solar CAPEX vs OPEX: Which Model Fits Your Business?
• Solar RESCO Model India: Guide for C&I Buyers

Sources

• CERC (Terms and Conditions for Tariff determination from Renewable Energy Sources) Regulations, 2024, Regulation 48, as reproduced in CERC order in Petition No. 175/GT/2024 (20 March 2025).
• IRENA Renewable Power Generation Costs in 2024.
• NREL Annual Technology Baseline 2024.
• IEA Renewables 2024.
• IEC 61724 series, Photovoltaic system performance.
• MNRE O&M Guidelines for Solar PV Plants.
• Manufacturer recommended maintenance schedules.
• IEA PVPS Task 13 Report on PV Performance and Reliability.
• Mercom India Solar Market Reports.