Solar for Flour Mills: Sizing, Roof, Approvals and Payback (50 kW+)

Solar suits a flour mill whose grinding runs in daylight, because most of the energy is then used on site. For 50 kW or more, size from twelve months of bills against daytime use and sanctioned load, check the roof and the dust hazard, pick net metering or a captive route by size, and test payback with the published band of ₹24,000–32,000 per kW excluding GST.

What the mill's load looks like

A flour mill is a motor load. Roller mills, sifters, purifiers, elevators, blowers, conveyors and packing lines run for the shift, and a mill that grinds in the daytime puts much of its consumption in sunlight hours. That is the good case. The weaker case is a mill that runs two or three shifts or mostly at night, where solar covers only part of the bill. Look at the hour-wise pattern on your meter data if the DISCOM or your meter provides it, or at the daytime share you can estimate from the shift plan.

Motors bring two technical points. Large motors starting on a weak LT feeder cause voltage dips that can trip grid-tied inverters, so ask the designer for the inverter's voltage and frequency settings and for a power factor check. And a mill with a low power factor pays a penalty that solar does not remove, so look at power factor correction alongside the solar plan.

Sizing from the bill

• Daytime share: the fraction of units consumed between about 8 am and 5 pm. Size so that most solar energy is consumed on site.
• Sanctioned load or contract demand: net-metering rules usually cap the plant against it. Test your headroom with the sanctioned load calculator.
• Common-month use, not peak: size for the month that is typical, not the heaviest one.
• Transformer headroom: the DISCOM checks whether the transformer serving you can take the plant.

As a planning rule, rooftop needs about 100 sq ft per kW and north India generates about 120 units per kW per month. So 50 kW is about 5,000 sq ft and 6,000 units a month; 100 kW is about 10,000 sq ft and 12,000 units. Put your own figures into the solar calculator.

Roof or ground, in a mill compound

Roller mill buildings are tall and their roofs are small, so the usable area is often on the godowns, the packing hall and any sheds beside the mill. These are usually lightly sloped sheet or RCC roofs. Check the structure before you plan the layout; the roof load calculator gives the order of magnitude. Where roofs are weak, shaded by the mill building, or crowded with vents and exhausts, a ground-mounted plant on spare land trades more cable and land use for a simpler structure. Shading from the tall mill block on the godown roofs next to it is common, so ask for a shadow study before you count area.

Risks that belong to a flour mill

On the dust hazard, treat your own safety assessment as the authority. Section 37 of the Factories Act, 1948 required all practicable measures against explosive or inflammable dust in a factory where it arises, and the Bureau of Indian Standards has a code on fire safety in flour mills, IS 13045. Labour law has since been consolidated, so confirm with your safety officer which provision applies today. Tell your insurer about the plant, and ask the designer to coordinate cable routes and equipment locations with your hazard assessment before anything is fixed to the roof.

Approval route by size

Rooftop plants within the state's net-metering limits go through the DISCOM's process: feasibility, application, inspection, meter and commissioning. Plants beyond the limit, or on land away from the mill, may fall under captive or open-access rules with their own approvals and charges. Read the net-metering explainer and the open access solar page. The Electricity (Rights of Consumers) Rules, 2020 require the distribution licensee to run an online application portal, a tracking system and a single point of contact, and to complete the study within the time set by the state commission. State limits and tariffs differ and change, so confirm the current regulation with your DISCOM.

Payback logic with the published band

Take the cost from the band: ₹24,000–32,000 per kW excluding GST, so ₹12–16 lakh for 50 kW and ₹24–32 lakh for 100 kW, with larger plants toward the lower end. Estimate annual units from the planning rule, multiply by the energy rate on your bill, and divide cost by saving. The result is a simple payback and is indicative. It ignores degradation, maintenance and tariff changes. Run it in the payback calculator and read the solar finance page for funding options. Fixed charges and demand charges are not reduced by solar in most cases, so a mill on a demand-based tariff saves on the energy component only. Exports earn what your state's rules give, which may be less than the retail rate.

How Secured Engineers helps

We design and install C&I solar plants for factories and agro-processing sites from 50 kW. Design is done in-house, and Fire NOC, CEIG and DISCOM net-metering applications are filed in-house, which matters in a mill where the fire design and the electrical design share the same roof and the same hazard assessment. Mechanical, electrical, plumbing, fire and solar work can sit under one contract. We work from offices in Noida (Delhi NCR) and Ludhiana, with 535+ projects across 18+ states and 89.77% repeat clients.

Send a twelve-month bill, the sanctioned load and a few photographs of the godown and mill roofs, and we will tell you what size is feasible and what to check. See solar for factories, message us on WhatsApp, call +91 70099 85817, or ask for a free proposal.