Solar for Flour Mills & Small Businesses: A Buyer Guide

Why solar fits a flour mill or small business

A flour mill, a small workshop, a cold store or a tailoring unit has one thing in common with a home that works from nine to five: its power use is concentrated in daytime. Solar panels produce electricity only when the sun is up, so the closer your working hours are to daylight, the more of the solar power you use directly and the less you depend on net metering credits.

For a typical atta chakki the heaviest electrical load is the grinding motor. Mills in towns and villages around Basti, Gorakhpur or Gonda often run from early morning to late afternoon, with a peak during the wheat-grinding season. That pattern lines up well with the hours of strong sunshine, which in most of Uttar Pradesh means roughly ten in the morning to three in the afternoon.

Electricity is also a recurring cost you cannot negotiate: a diesel generator, a commercial tariff and fixed charges all arrive every month. A rooftop system turns part of that cost into a one-time investment, and the panels carry long warranties. Solar is not right for every shop, so this guide walks through the numbers first.

Start with a load study, not a quotation

Before you speak to any installer, write down what actually draws power in your premises. Look at the nameplate on each motor and machine, which shows the rating in horsepower (HP) or kilowatts (kW). One horsepower is about 0.75 kW, so a 10 HP mill motor is roughly 7.5 kW at full load. Note how many hours each machine runs on a normal day and on your busiest day.

Then collect the last twelve electricity bills. A single month can mislead you because grinding seasons, festivals and summer cooling change consumption. Twelve bills show your real average and your highest month. They also show your sanctioned load, tariff category and any fixed or demand charges, all of which affect how much solar you can usefully connect.

• List every motor and machine with its rating and daily running hours.
• Note whether your connection is single-phase or three-phase, because this limits the inverter type.
• Record your sanctioned load in kW from the bill, since a net-metered system is normally limited by it.
• Mark which loads must keep running in a power cut, such as a cold room, and which can wait.
• Photograph the meter, the main panel and the roof so an installer can give a more accurate first estimate.

How much solar does a flour mill need?

The right size depends on how many units you use in a day. As an illustration only, imagine a mill with a 10 HP motor, about 7.5 kW at full load, that runs eight hours a day at an average of seventy percent load. That is roughly 7.5 × 0.7 × 8, or about 42 units a day, plus a little for lights and a small office. A rooftop system in this part of India generates roughly four to five units per kW per day on average, so covering all of that daytime use would need something in the range of 9 to 11 kW of panels.

In practice many owners choose a system smaller than their full daytime load. A smaller system gets used almost entirely, so every unit it produces replaces a unit you would have bought, and the payback is easier to predict. Sizing larger only makes sense if your roof has space, your sanctioned load allows it, and your DISCOM's net metering rules give you fair credit for the surplus.

A third constraint is roof space. Plan for roughly eight to ten square metres of shadow-free roof per kW. A 10 kW system therefore needs around 80 to 100 square metres, which many mill buildings can offer, but a shop on a crowded market street may not. An installer should visit, measure and draw the layout before quoting.

Commercial tariffs and why subsidy does not apply

Homes and businesses are billed under different tariff categories. Commercial and industrial connections may pay a different rate per unit, and some also pay a fixed charge based on sanctioned load or a demand charge based on peak use. The exact structure is set by the state regulator and changes from time to time, so read the tariff category printed on your bill rather than relying on a general figure.

The central rooftop subsidy under PM Surya Ghar is meant for residential households. A shop, mill or workshop on a commercial connection is generally not eligible for it. This matters because many sales pitches quote a subsidy-reduced price. For a business you should ask for the full installed price and judge the project purely on the savings it produces. If any scheme or benefit does apply to your category, a trustworthy installer shows you the official notice instead of just quoting a number.

Some businesses may be able to claim depreciation on solar equipment under income tax rules, which can reduce taxable profit in the early years. Whether and how much you can claim depends on your business structure and the current rules, so speak to your accountant before you count on it in your calculation.

Working out payback honestly

Simple payback is the installed cost divided by the yearly saving on your bill. Suppose, purely as an illustration, that a system costs ₹5,00,000 and saves ₹1,20,000 a year on electricity. The simple payback is about four years and two months. If you also needed to replace the inverter once in the system's life for, say, ₹60,000, the lifetime cost rises and the effective payback becomes slightly longer.

The saving itself depends on the rate you pay per unit and how many solar units you actually use. If your tariff is higher, each solar unit saves more. If your system produces more than you use and your DISCOM credits exports at a lower value than the retail rate, the extra units are worth less than the ones you consume yourself. This is one more reason not to oversize.

Be wary of any quotation that promises a fixed payback or a zero bill without showing its assumptions. A responsible proposal lists the expected generation, the tariff it assumed, the share of units used on site, and the cost of replacing the inverter. If these are missing, ask for them in writing before you decide.

Approvals, net metering and rented premises

A grid-connected business system needs DISCOM approval before it is commissioned. Your installer normally files the application, but you should know the stages: registration, technical feasibility, installation, inspection and the fitting of a bi-directional meter. Ask for the application number and the name of the person who will track it.

If you do not own the building, you need the owner's written permission and clarity on who owns the system if the lease ends. Rented markets cause this problem often, and a landlord who agrees verbally today may not agree in three years. Put the roof access, ownership of the panels and what happens at lease end into a simple signed letter before you pay anything.

Finally, check whether your roof can carry the structure. Old asbestos or tin roofs and thin slabs may need strengthening. Ask the installer how the mounting structure is fixed and whether the roof will stay waterproof.

A short checklist before you sign

Compare two or three written quotations line by line, not by the total alone. A lower price can hide a smaller inverter, cheaper cables or missing earthing and surge protection.

• Panel brand, model, wattage per panel, number of panels and the performance warranty.
• Inverter brand, rating, warranty period and who handles service in your district.
• Mounting structure material and wind-load design, since roofs in open areas face strong winds.
• Earthing, lightning protection and surge protection included in the price.
• Who files the DISCOM application and net metering paperwork, and who pays any fees.
• A payment schedule tied to delivery, installation and commissioning, not a full advance.
• A written service contact and a plan for cleaning and annual inspection.