Industrial Rooftop Solar vs Open Access Solar in India

1. The Decision In One Page

Industrial rooftop solar generates electricity at the factory and uses it on-site, subject to configuration and applicable rules. Open access solar allows eligible consumers to procure electricity from an off-site project through the electricity network under an applicable arrangement.

Rooftop solar typically requires suitable roof area and electrical infrastructure. Open access does not require the consumer’s factory roof for the off-site project, but involves delivery arrangements, contracts and applicable charges. Captive generation is a specific ownership and consumption structure; it is not synonymous with open access.

There is no universal winner. The right structure is the one that fits technical, financial, operational and regulatory requirements.

2. What Is Industrial Rooftop Solar?

Industrial rooftop solar is a photovoltaic system installed on the roof of a factory, warehouse, manufacturing plant or commercial building. It converts sunlight into electricity used by machinery, motors, lighting, HVAC systems, compressors and other equipment.

A typical installation includes solar modules, mounting structures, grid-connected inverters, DC/AC protection, cables, earthing, monitoring and grid integration equipment as required.

During daylight, generated electricity offsets electricity that would otherwise be drawn from the grid. If generation is below consumption, the shortfall comes from the grid. Surplus treatment depends on the approved configuration, metering and applicable DISCOM rules.

Potential benefits include reducing grid energy purchases, using existing roof space, aligning generation with daytime operations and supporting long-term energy planning. Actual savings depend on tariff, self-consumption, generation and billing treatment.

3. What Is Open Access Solar In India?

Open access allows eligible consumers to procure electricity from a generating project other than their conventional local supply arrangement, using the electricity network under the applicable regulatory framework.

Common structures include:

• Third-party open access: a consumer purchases electricity from an independent renewable generator under a permitted contract.
• Captive solar: qualifying consumers invest in or own generation for their own consumption, subject to applicable requirements.
• Group captive: multiple qualifying consumers participate in a project through an eligible ownership and consumption structure.

These structures have different legal and commercial requirements. A proposal should not assume every captive or group captive project receives identical charges or exemptions.

For Gujarat projects, assess the current applicable GERC regulations and orders, DISCOM requirements, consumer voltage/demand, connectivity, metering, and project-specific approvals. Depending on the structure, charges and considerations may include transmission and wheeling charges, losses, cross-subsidy surcharge, additional surcharge where applicable, banking/settlement provisions, and scheduling requirements. Applicability must be confirmed for the specific project.

4. Cost And Roi Comparison

The meaningful comparison is the total cost of obtaining usable renewable electricity over the project’s life, not just installation price.

Rooftop cost considerations:

1. Initial investment or financing
2. Expected generation and self-consumption
3. O&M, cleaning and monitoring
4. Inverter or major equipment replacement if required
5. Electrical upgrades, roof work and grid integration
6. Residual grid purchases and applicable charges

Open access cost considerations:

1. Contracted energy price or project investment
2. Applicable network charges and losses
3. Applicable surcharges, levies and settlement costs
4. Metering, scheduling and approvals
5. Contract duration, payment terms and minimum obligations
6. Residual electricity purchase

Industrial electricity bills typically bundle energy, demand, fixed, time of day, and other charges. Reducing energy purchases doesn’t automatically reduce fixed or demand charges. Calculate savings from your actual bills, not a generic tariff assumption.

Simplified rooftop payback formula:

Simple Payback (years) = Initial Project Cost / Annual Net Savings

This is a directional indicator, not a full investment valuation. It excludes cash flow timing, financing costs, taxes, degradation, tariff changes, and replacement costs. For larger projects, you should also model NPV, IRR, debt servicing, and sensitivity scenarios.

5. Illustrative Financial Example: 500 KW Rooftop Solar

The figures below are for illustration only. They are not a Dhriya quotation or a verified Gujarat tariff.

Calculation:

• Self consumed electricity = 7,50,000 x 90% = 6,75,000 kWh
• Illustrative avoided energy charges = 6,75,000 x Rs. 8 = Rs. 54 lakh/year
• After O&M = Rs. 54 lakh minus Rs. 2 lakh = Rs. 52 lakh/year net savings
• Simple payback = Rs. 2 crore / Rs. 52 lakh, approximately 3.85 years

This example excludes financing, taxes, degradation, inverter replacement, tariff escalation, demand charge changes, export credit, and other unmodeled costs. Actual performance and payback may differ materially for your facility.

6. Why Your Factory Load Profile Matters

Two factories can consume the same monthly units but have different solar economics because timing matters. A day-shift factory with substantial daytime demand may directly use a larger share of rooftop generation. A facility with substantial night-shift consumption may need to assess grid supply, eligible settlement arrangements or storage.

Review monthly consumption, interval/hourly load data where available, day/night demand, weekday/weekend patterns, seasonality, planned expansion, existing renewable systems, contracted demand and time-of-day tariffs.

7. Space, Roof Condition And Engineering Feasibility

Total roof area is not the same as usable solar area. Assess:

• Structural condition and load capacity, with qualified structural review
• Roof type, waterproofing, penetrations and corrosion protection
• Shading from buildings, trees, chimneys and equipment
• Transformer, switchgear, cable routes and connection capacity
• Safe access for inspection, cleaning and emergency response
• Installation sequencing, lifting, electrical isolation and shutdown planning

If roof space is insufficient, off-site procurement may be evaluated, but it is not automatically more economical. Carports or other suitable on-site areas may also be considered where permitted and feasible.

8. Transformer Capacity, Grid Integration And Safety

A solar system must be integrated with the factory’s electrical infrastructure. Review transformer loading, switchgear, inverter ratings, cable sizing, protection coordination, anti-islanding, earthing, lightning protection, metering and grid connectivity.

Coordinate with facility electrical and maintenance teams. Identify activities possible during production, those requiring isolation, planned shutdown windows, safety responsibilities, testing and commissioning procedures.

9. Open Access: Grid Delivery, Charges And Contracts

Generation price is only one part of open access economics. Confirm delivered electricity cost after applicable charges and losses, energy matching, contracted capacity, minimum purchase/payment terms, banking and settlement where permitted, approvals, metering and regulatory changes.

A proposal should state the generating project, structure, energy price, charges, approvals, expected delivery and settlement, contract duration, termination conditions, payment obligations, O&M/compliance responsibilities, assumptions and exclusions.

For captive/group captive projects, document how ownership and consumption requirements will be met and maintained. Obtain project-specific legal and regulatory review.

10. Battery Energy Storage Systems (BESS)

A battery stores electricity for later use. It may help shift suitable surplus solar energy, manage selected peak periods or support specific operational requirements. It is not necessary for every industrial solar installation.

Evaluate required power and duration, usable capacity, charging/discharging schedule, efficiency, degradation, safety, installation conditions, integration, maintenance and replacement costs. Assess battery economics separately from solar because storage adds capital and operating considerations.

11. Can Rooftop And Open Access Be Combined?

A business may evaluate on-site rooftop solar alongside off-site renewable procurement, subject to eligibility, regulations and contracts. This may be relevant where roof space cannot meet all renewable energy objectives.

Coordinate existing generation, load forecasts, remaining procurement needs, captive/open access conditions, grid connection, metering, settlement, contracts, financing and future expansion. The goal is a justified energy strategy, not maximum installed capacity at any cost.

12. Industrial Solar Decision Factors

Before deciding, establish:

1. Annual electricity consumption and interval load profile
2. Daytime load and operating shifts
3. Tariff and bill components that can actually be avoided
4. Usable roof area and roof life
5. Transformer and electrical capacity
6. Investment, financing or PPA preferences
7. Project scale and technical feasibility
8. Current regulatory requirements and approvals
9. Expected net savings and risks
10. Responsibility for engineering, monitoring and maintenance

13. Ten Questions Before Committing

1. What is our 12 month electricity consumption?
2. What are our daytime, nighttime, and seasonal load patterns?
3. What tariff and billing structure applies to us?
4. How much structurally suitable roof space do we actually have?
5. What is the roof’s condition and remaining useful life?
6. Can our electrical infrastructure accommodate the system?
7. Are we considering capex, financing, PPA, or captive?
8. Which current Gujarat rules, charges, and approvals apply to us?
9. What are the realistic costs, net savings, and financial risks?
10. Who manages engineering, installation, monitoring, and maintenance?

14. How Dhriya Renewable Energy Can Help

Dhriya Renewable Energy can support industrial solar planning through preliminary feasibility review, site survey and engineering, project sizing and financial evaluation, procurement and installation planning, commissioning and ongoing support, according to the agreed project scope.

For off-site open access or captive projects, eligibility, ownership, procurement, charges and compliance must be established for the specific transaction.

For a preliminary assessment, prepare:

• Last 12 months of electricity bills
• Sanctioned load and contracted demand
• Factory operating hours and shifts
• Roof area, roof type and photographs
• Transformer and electrical details
• Existing solar system details
• Planned factory expansion