Solar for Forging and Re-rolling Units: Sizing, Roof, Approvals and Payback (50 kW+)

A forging or steel re-rolling unit can use rooftop solar well, because furnaces, reheating and mill drives run through daylight shifts. The sizing limit is rarely roof area. It is the daytime base load your plant actually holds, your sanctioned load or contract demand, and the power quality on your bus. Size to the first two, survey the third, and check payback against the tariff you pay in solar hours.

Size the plant from the bill, in four steps

1. Find the daytime share. Take interval data if your meter records it, or the shift pattern. A unit running one or two day shifts uses most of its energy while the sun is up. A three-shift unit with a heavy night furnace load uses less of a solar plant's output. Solar produces for roughly the middle eight hours of the day.
2. Find the daytime base load. This is the load that is on even in the quietest daylight hour, not the average. A plant sized above it exports at those hours.
3. Check headroom. Most DISCOMs cap rooftop capacity at or near the sanctioned load or contract demand, and some states set a lower percentage. Our sanctioned load calculator shows the ceiling before you design.
4. Take the smallest of three numbers: daytime base load, headroom, and roof or land area at roughly 100 sq.ft per kW.

Then consider what changes in your plant over the next five years. Bureau of Energy Efficiency baseline audits of Ludhiana forging units assess replacing fuel-fired reheating furnaces with induction units. If you are considering that, remember that electrifying heat adds load, so decide that first and size solar to the new daytime load rather than the old one.

What is different about this sector

Power quality is the sector-specific risk

Induction heating and drives distort the supply. Harmonics, flicker and a poor power factor are not reasons to skip solar, but they must be measured. A power quality survey of the incoming supply, taken across a full production cycle, tells you the voltage and current distortion that the inverter will see, and whether the existing capacitor bank is likely to resonate. Without it, the usual symptoms are inverter trips, nuisance protection operation and complaints from the DISCOM. Ask the designer to state which standard the inverter's harmonic output complies with and how the plant is protected against grid distortion.

Roof or ground?

Forge shops and rolling mill sheds are tall, hot and often crowded with crane gantries, ridge vents and exhaust stacks. Check the sheeting age and the purlin capacity with the roof load calculator and a structural survey, and plan roof access away from furnace exhaust. Many units in industrial estates have open land inside the boundary. A ground-mount on that land avoids roof issues, though it uses land you may want for expansion; the plant area calculator gives the area. Keep cable routes and modules clear of hot work, flue gas outlets and scrap handling.

Which approval route applies by size?

Open access and captive routes follow national rules as well as state ones. The Green Energy Open Access Rules, 2022 lowered the open access threshold for green energy from 1 MW to 100 kW, with approval deemed granted if not decided in 15 days. The Electricity Rules, 2005 define a captive plant by ownership and consumption tests; the rule was amended in March 2026, so read the current text. Our open access guide compares the routes.

Payback: use the tariff that applies in solar hours

Our published benchmark for turnkey C&I rooftop solar is ₹24,000 to ₹32,000 per kW excluding GST. At 100 kW, the cost page shows ₹28 to ₹32 lakh; at 250 kW about ₹68 to ₹75 lakh; at 500 kW about ₹1.30 crore. Annual value is the units generated and used on site, multiplied by the energy charge you avoid, which is not the same as the average rate on your bill. Demand charges, fixed charges and taxes do not fall unit for unit with solar.

Check the time-of-day structure too. Under the 2023 amendment to the Electricity (Rights of Consumers) Rules, commercial and industrial consumers above 10 kW are on time-of-day tariffs, with a lower tariff during the solar hours your state commission sets. For a solar plant, the avoided cost is the solar-hour rate, so a unit generated at noon may be worth less than the bill's average. The solar calculator gives a first view; for a decision, ask for payback shown as scenarios by self-use share.

How Secured Engineers helps

We design in-house and take MEPF and solar under one contract, so the HT connection, protection and DG interlocks are designed with the solar plant. Fire NOC, CEIG and DISCOM net-metering applications are filed in-house. We work from offices in Noida (Delhi NCR) and Ludhiana, with 535+ projects across 18+ states and 89.77% repeat clients. We do not cite a specific forging or re-rolling client here. Start with your last twelve bills and your shift pattern.

See solar for factories for how we scope a plant. To discuss yours, WhatsApp us your bills, call +91 70099 85817, or ask for a free proposal.