Solar for Rice Mills and Agro Processing Units in Tamil Nadu

A rice mill is a building full of motors. Dehuskers, separators, polishers, elevators, blowers and dryers all start and run together, and the bill reflects it.

What makes the sizing interesting is the calendar. Milling is seasonal, so a mill that consumes heavily for five months and lightly for seven has to be sized around the average rather than the peak, or a good part of the array spends half the year exporting at a credit below the tariff it could have avoided.

What decides the answer here

• Industrial LT runs roughly ₹6.50 to ₹7.50 a unit, and an HT connection adds demand charges on top of the energy charge.
• Motor load is steady while running, which is ideal for solar, but only during the months the mill is running.
• Size to the off-season as well as the season. Capacity idle for seven months earns the export credit, not the tariff.
• Shed roofs are large and usually under-used, so roof area is rarely the binding constraint here.
• Sanctioned load is the real ceiling in Tamil Nadu, not the roof.

Where the units go in a mill

• Paddy cleaning and dehusking, the first and one of the largest motor groups.
• Polishing and grading, which runs continuously while the line is on.
• Elevators and conveyors, small individually and significant together.
• Blowers and aspiration, running whenever the line runs.
• Dryers, where fitted, which are the heaviest seasonal load of all.
• Lighting and the office, modest but running through daylight.

The pattern is steady draw during a milling shift and very little between. That suits a rooftop array well, provided the shifts fall in daylight, which for most mills they do.

Sizing around a seasonal year

This is the decision that separates a good proposal from a generic one. Take twelve months of bills, not three, and look at the shape.

A mill consuming 40,000 units a month in season and 8,000 out of it has an annual average nearer 21,000. An array sized to the in-season figure will export roughly half its output for over half the year. An array sized nearer the average is consumed almost entirely, at the full tariff, all year.

The exception is a mill with year-round parboiling or an attached godown operation, where the baseline is high enough that seasonal variation stops mattering. audit it per watt is worth reading before comparing proposals, because this is exactly the place a quotation gets oversized.

The roof and the sanctioned load

Mill sheds are large, and roof area is rarely what limits the system. Two other things usually do.

• Sanctioned load. In Tamil Nadu capacity is capped at your sanctioned load, so a mill sanctioned at 100 kW cannot install 200 kW of solar whatever the shed would hold. Enhancing the sanctioned load is a separate DISCOM application and should be started early if it is needed.
• Roof condition and purlin capacity. Mill roofs carry dust and vibration and are often older than the machinery under them. Assess before designing, and replace sheeting before installing rather than after.

The tax side, which is not the residential subsidy

The PM Surya Ghar subsidy does not apply here. It is a residential scheme, and any proposal that deducts it from a commercial quotation is deducting money the business will not receive.

What a business gets instead is accelerated depreciation. Solar power generating systems sit in a 40 percent depreciation block under Appendix I of the Income Tax Rules, claimed under Section 32, against an ordinary building at 10 percent and general plant and machinery at 15 percent.

The timing decides the first year. A system commissioned and put to use for 180 days or more in the financial year takes the full 40 percent; commissioned later and the first year is halved to 20 percent, with the balance carried forward. Our guide to how to calculate it works through the arithmetic on a real invoice.

GST on a turnkey installation works out near 8.9 percent under the 70:30 composite supply rule, with the module and system portion at 5 percent. That input is creditable for a GST-registered business, which residential buyers cannot do.

Frequently asked questions

How much does solar cost for a rice mill?

It depends on the size the sanctioned load and the consumption pattern justify rather than on the shed area. As a reference, installed cost per watt falls as systems grow, from the band that applies to small rooftop systems down towards ₹45 to ₹55 per watt at 100 kW and above.

Is solar worth it for a seasonal rice mill?

Yes, if it is sized to the annual average rather than the in-season peak. Capacity that is idle for the off-season months exports at a credit below the tariff it could have avoided, which lengthens the payback considerably.

Can the mill shed roof take solar panels?

Usually, after a check on purlin spacing, section and roof condition. Mill roofs carry dust and vibration and are frequently older than the plant beneath them, so condition matters more here than on a newer industrial shed.

What limits the system size at a rice mill?

Almost always the sanctioned load rather than the roof. Tamil Nadu caps permitted solar capacity at the sanctioned load or contracted demand, so raising it is a separate DISCOM application that should start early.

Do rice mills get a solar subsidy?

Not PM Surya Ghar, which is residential. A mill claims accelerated depreciation at 40 percent and takes GST input credit on a turnkey installation.

Send twelve months of bills, not three

The seasonal shape is the whole sizing question, and it is invisible in a quarter of data. Send twelve months, the sanctioned load and a roof plan, and we will size to what the mill actually consumes across a year.

We work across the Thanjavur, Trichy, Villupuram and Nagapattinam belt.

Sources

Tamil Nadu Electricity Regulatory Commission tariff orders, for LT and HT consumer categories and energy charges

Blues Renewables generation records, Tamil Nadu rooftops, for the figure of about 4.8 units per kW per day

Income Tax Act 1961 Section 32 and Appendix I of the Income Tax Rules, for the 40 percent depreciation block and the 180-day rule

GST notifications on solar photovoltaic modules and solar power generating systems, effective 22 September 2025

Published industrial LT and HT energy charges for agro processing units, 2026