Industrial Solar EPC in India: Contracted Load, CEIG & the Real ROI Levers

For a factory or warehouse, rooftop solar is not just an energy bill conversation - it's a contracted load, demand charge, and tax planning conversation. Get those three right and the project pays for itself far faster than the brochure number. Where the roof runs out, open access picks up the rest of the load.

Rule 1: System size ≤ contracted load

Nearly every state's net-metering regulation caps the solar plant at your contracted (sanctioned) load, in kW. A factory with 200 kVA contracted demand (≈ 180 kW) cannot install a 250 kWp plant under net metering, no matter how much roof it has.

Practical implication:

• Audit your last 12 months of MD (Maximum Demand) before sizing
• If you're consistently hitting 90%+ of contracted demand, consider revising contracted load upward before the solar application - it expands your eligible system size
• For factories with surplus roof but low contracted load, gross metering, behind-the-meter captive consumption without export, or open access is the workaround

Rule 2: Electrical inspectorate (CEIG) certification

In most states, a rooftop plant above roughly 50 kW DC (which a 1.1-1.15 oversizing buffer crosses quickly) requires inspection and approval from the Chief Electrical Inspector to Government (CEIG / CEI) before commissioning. The threshold and the paperwork differ state to state - confirm yours before you fix a commissioning date.

What CEIG actually checks:

• Structural design with wind-load calculations
• Earthing and lightning arrestor design
• HT/LT interconnection drawings, signed by a licensed Class-A electrical contractor
• DC/AC SLD and protection coordination
• Cable sizing and conduit/tray routing

Skipping or mis-filing CEIG is the single most common reason industrial commissioning slips by 4-8 weeks. Build it into your timeline from day one.

Rule 3: Demand charges are where the hidden savings live

Most industrial bills have two main components: energy charges (per unit) and demand charges (per kVA of contracted/recorded MD). Energy charges run ₹6.5-₹8.5/unit for HT and ₹8-₹10 for LT industrial across most states. Demand charges add another ₹350-₹500/kVA/month.

A well-designed solar plant doesn't just cut energy units - it can shave recorded MD during daytime peaks if sized and configured against the load curve. On a 500 kVA factory, even a 15-20 kVA reduction in recorded MD is ₹7,000-₹9,500/month, recurring, on top of the unit-level savings.

This is why we always ask for 15-minute interval data before sizing. A monthly bill isn't enough.

Rule 4: Open access for loads the roof can't cover

Above ~1 MW of consumption, most large plants can't fit enough capacity on their own roof. That's where open access comes in - third-party PPA, captive or group captive, wheeled from an off-site solar or wind-solar hybrid park through the state grid. Typical landed tariffs run ₹3.2-₹4.8/unit depending on state charges, against HT grid tariffs of ₹7-₹9. The levers to check state by state: wheeling and transmission charges, cross-subsidy surcharge and additional surcharge, banking rules, and the 26% equity threshold for group captive.

Rule 5: Accelerated depreciation is real money

Under Section 32 of the Income Tax Act, solar plants qualify for 40% depreciation in year 1 (plus an additional 20% in some cases under specific provisions), on the eligible plant cost. For a profitable factory in the 25% corporate tax slab:

• ₹1 crore plant
• Year-1 depreciation: ₹40 lakh
• Tax shielded in year 1: ~₹10 lakh

That alone shifts payback from ~5 years to ~3.5 years for taxable entities. LLPs, private limiteds and partnership firms all qualify. Co-ops and Section 8s don't.

What turnkey EPC actually means for industrial sites

• 12-month consumption + 15-min interval load audit
• Structural assessment of the roof (load capacity, age, sheet type)
• DPR with single-line diagram, structural drawings, GA drawings
• DISCOM application + technical feasibility (or open access application where relevant)
• CEIG drawings, submission, inspection
• Procurement against ALMM List-I + BIS-certified inverters
• Installation under a licensed electrical contractor
• Pre-commissioning, CEIG visit, joint commissioning with the DISCOM
• SCADA / remote monitoring with per-string visibility
• 30-year support, not 5-year warranty hand-off

Multi-vendor projects fail not at install but at the CEIG-to-commissioning seam. One EPC partner owns that seam.