What to check first
- A factory operating from 9:00 AM to 5:00 PM can use most solar output immediately if its daytime base load is high enough. That may avoid the cost of batteries.
- Compare the billed industrial tariff of about ₹7.50 to ₹10.50+ per unit with an indicative solar levelised cost of ₹2.50 to ₹3.50 per unit. Confirm both against your site.
- Trapezoidal sheets use sealed fasteners on raised crests. Standing seam sheets can take clamps without roof penetrations. Survey the roof before choosing a mount.
- Plant sizing must account for contract demand in kVA, transformer headroom, generator operation and the DISCOM rules for your connection.
Electricity can take a large share of a factory's operating budget. For fabrication, plastics, textile, auto parts, packaging and agro-processing units around Srikalahasti, Renigunta and Sri City, the share may be 15% to 35%, depending on the process. HT and LT bills also carry fuel adjustment charges. Start with your own 12 months of bills to establish the real cost.
A broad metal roof gives you space. The more useful advantage is a steady load while the sun is out. If motors, compressors and processing equipment run through daylight, the factory can use solar units as they are made and buy fewer units from the grid. That saving depends on the actual production schedule.
This guide covers roof checks, plant sizing, grid arrangements and funding choices for a factory installation. For related site types, see our commercial solar options, manufacturing systems and warehouse solar projects.
Match solar generation to factory demand
Your self-consumption ratio is the share of solar power used behind the meter instead of exported. Export credits under net metering can be lower than the retail tariff avoided when the factory uses a unit itself. Check the applicable DISCOM settlement rule before assigning a value to exported units.
Consider a single-shift plant open from 8:30 AM to 5:30 PM. Generation starts around 6:30 AM, peaks roughly between 11:00 AM and 1:30 PM, and eases towards 5:30 PM. CNC machines, conveyors, motors, compressors and chillers may operate across the same hours. Compare an interval load profile with an hourly generation forecast to see the overlap.
If the factory's minimum daytime demand exceeds the proposed plant's peak output, it may consume nearly 100% of generation on site. Power goes from the roof to the LT distribution panel, removing the need for batteries for ordinary daytime use. Check weekend shutdowns, lunch breaks and seasonal shifts before assuming that result.
Ask for a daytime load chart before accepting a no-battery design. The grid covers a shortfall when clouds reduce solar output and supplies power after sunset. Solar meets part of the load when it is available.
Survey the metal roof and supporting steel
Most industrial sheds use pre-engineered buildings or trusses under corrugated metal sheets. The mounting method must suit both the sheet and the supporting steel. Record corrosion, loose fasteners, drainage paths and existing leaks before the installation starts.
Trapezoidal GI and pre-coated sheets
Short anodised aluminium rails can sit on the raised crests of trapezoidal sheets. Stainless steel self-drilling screws pass through UV-resistant EPDM sealing washers. Keeping penetrations away from drainage valleys reduces leak risk. Ask to see the fixing position, sealing detail and monsoon inspection plan.
Standing seam sheets
Aluminium clamps grip the vertical ribs of a standing seam roof without drilling through the sheet. Even then, the installer must verify the seam shape, pull-out strength and the roof maker's warranty conditions. Obtain written roof manufacturer approval if that warranty requires it.
Dead load and wind uplift
Panels, supports, walkways and cables add roughly 12 to 15 kg per square metre of dead load. An engineer should inspect purlins, rafters, trusses and sheet gauge before approving the layout. Wind uplift is also significant on coastal sites. Check the final mount design against IS 875 Part 3 and the actual site exposure.
Size the plant and plan diesel backup
Roof area is only one limit. Contracted maximum demand, HT or LT metering, transformer capacity and daytime load also shape the right plant size. In southern Andhra Pradesh, allow about 4.0 to 4.5 units per kWp each day on an annual average, or 1,400 to 1,600 units per kWp each year. Plan for roughly 80 to 100 sq ft of clear roof per kWp, then refine both estimates through a site audit.
| Plant capacity (kWp) | Clear roof area (sq ft) | Estimated yearly output (units) | Estimated monthly offset (units) | Example factory use |
|---|---|---|---|---|
| 50 kWp | 4,000 to 5,000 | 70,000 to 80,000 | ~5,800 to 6,600 | Small machine shops, grain mills and plastics moulding |
| 100 kWp | 8,000 to 10,000 | 1,40,000 to 1,60,000 | ~11,600 to 13,300 | Fabrication, packaging and auto parts units |
| 250 kWp | 20,000 to 25,000 | 3,50,000 to 4,00,000 | ~29,000 to 33,300 | Textile processing, cold storage and pharmaceutical units |
| 500 kWp | 40,000 to 50,000 | 7,00,000 to 8,00,000 | ~58,000 to 66,600 | Heavy engineering, ceramics and chemical plants |
Diesel generator synchronisation
An ordinary grid-tied inverter requires a live grid reference and disconnects during an outage to prevent islanding. A factory on diesel backup can use a DG-solar synchronisation controller so the inverter follows the generator's AC supply. The design must suit the generator and switchgear, then be commissioned accordingly.
The controller adjusts solar output as factory demand changes. It should keep the generator above its minimum operating load, often 30% to 35% of rated capacity, and prevent reverse power into the alternator. Diesel savings of up to 60% during daytime outages are possible in a suitable load pattern, but your operating records determine the estimate.
Do not connect grid-tied solar to a diesel-backed bus without the right synchronisation controller. Reverse power may trip the generator and damage electrical or mechanical components.
Check ALMM and DCR status before ordering
MNRE's Approved List of Models and Manufacturers covers modules in List-I and cells in List-II. Following the June 2026 List-II shift, ask for the exact module model, cell origin and the compliance route that applies to your project before paying an advance.
Ray2Volt prepares new commercial and industrial quotations with DCR panels unless a verified exemption applies. The indicative DCR premium is ₹9 to ₹12 per Wp, or about ₹9,000 to ₹12,000 per kWp, against a non-DCR alternative. Check current model approvals, availability and DISCOM conditions. DCR status alone does not establish output or build quality.
Compare ownership with a RESCO agreement
You can own the plant or buy its electricity from an investor. Compare both routes with your own tariff, loan terms and operating schedule.
CAPEX means your business owns the plant
Under CAPEX, your company uses its own funds or equipment finance and keeps the value of the electricity it consumes. Eligible businesses may claim 40% accelerated depreciation on written down value under section 33 of the Income-tax Act, 2025. The rate is halved if the asset is used for less than 180 days in its purchase year. Confirm the current rate and your eligibility with your chartered accountant. Typical business payback is 3 to 5 years, depending on the site audit. A levelised cost below ₹3.00 per unit over a 25 to 30-year plant life is an illustrative estimate requiring project figures. See our depreciation guide.
OPEX or RESCO means buying the output
Under a Renewable Energy Service Company (RESCO) arrangement, a third-party investor funds, owns, installs and maintains the plant. The factory buys units at an agreed power purchase agreement tariff. An offer might be 20% to 40% below the prevailing grid tariff with no upfront plant capital. Check tariff escalation, minimum offtake and roof access terms before comparing it with CAPEX. Read our CAPEX and RESCO comparison and investor partnership information.
Some MSMEs may qualify for green equipment loans from institutions such as SIDBI or banks. Rates, tenure and whether bill savings can cover an EMI depend on the borrower and quotation. These figures are indicative, schemes change and you should confirm your eligibility. Ray2Volt does not give tax or investment advice.
Build in safe access and cleaning
Factories often leave more dust, soot and chemical residue on panels than nearby homes. A heavily soiled site could lose 10% to 25% of generation over a quarter. Compare actual output with the forecast and inspect the modules before setting a cleaning interval; exposure varies by process and season.
Include access and cleaning provisions in the initial roof drawing:
- Roof walkways: Anti-slip FRP or galvanised steel paths beside the rows let technicians inspect and clean panels without walking on fragile sheets.
- Fall protection: Stainless steel lifelines anchored to rafters protect people working at height. Check the design against your factory's safety requirements.
- Cleaning water: UPVC headers with quick-connect hose points near the ridge reduce the need to drag hoses over modules. A dusty site may need cleaning every 12 to 15 days. Remove grit carefully to avoid scratches.
Ray2Volt installations carry a 12-year panel product warranty, a 30-year panel performance warranty and an inverter warranty of 8 to 10 years depending on the model. We provide 5 years of free service for workmanship and balance of system, with an AMC available for up to 5 years. Local support comes from our registered office in Srikalahasti and branches in Tirupati, Nagari and Puttur.
Arrange a factory power audit
Before fixing plant size or payback, our engineers need to understand your power use and roof structure. The site audit covers:
- Twelve months of HT or LT bills and interval readings, including energy slabs, maximum demand and time-of-day charges. See our guide to reading a commercial electricity bill.
- A shade survey, with high-resolution 3D drone mapping where appropriate, to locate chimneys, vents and neighbouring obstructions.
- A physical check of shed sheets, purlins and trusses for repair needs and structural limits.
- Transformer headroom, short-circuit protection and the DISCOM connection requirements, checked with the relevant engineers.
Share your bills and roof details with Ray2Volt to begin a feasibility assessment.
Frequently asked questions
How much could a factory rooftop system produce in Andhra Pradesh?
For planning, allow roughly 4.0 to 4.5 units per kWp per day on an annual average, or 1,400 to 1,600 units per kWp per year. A 100 kWp system suggests about 1,40,000 to 1,60,000 units annually. Shading, orientation, cleaning and downtime affect the actual figure.
Which roof details help prevent leaks?
Standing seam clamps grip the ribs without piercing the sheet. Trapezoidal sheets need short rails with EPDM washers and stainless steel screws fixed on raised crests. Ask for the fixing drawing and sealing inspection plan after the roof condition survey.
Can solar run while our factory is on diesel backup?
A standard grid-tied inverter disconnects when grid supply fails. A properly designed DG-solar synchronisation controller can let solar run alongside the generator while keeping it above its minimum load. Suitable sites might reduce daytime diesel use by 50% to 70%; check the estimate against your load and outage records.
Can a factory claim the PM Surya Ghar subsidy?
No. PM Surya Ghar assistance, up to ₹78,000 for a 3 kW home system, is for eligible residential customers. Businesses may have access to 40% accelerated depreciation on written down value under section 33 of the Income-tax Act, 2025, GST input tax credits where eligible, and MSME finance. Rules can change. Confirm your case with your chartered accountant. Ray2Volt does not give tax or investment advice.
How much clear roof do we need for a 100 kWp plant?
Allow about 80 to 100 sq ft per kWp initially. A 100 kWp factory plant therefore needs roughly 8,000 to 10,000 sq ft of unobstructed shed or RCC roof. Walkways, setbacks, shading and structural limits can change the final layout.
Ray2Volt Solar Private Limited
We design, install, and service rooftop solar for homes and businesses across Tirupati district and Andhra Pradesh, from PM Surya Ghar residential systems to commercial and industrial plants. Every enquiry starts with a free power audit.
Assess your factory roof and power use
Send your recent electricity bills and roof dimensions. Our engineers will check the layout, estimate generation and show a payback range based on the site audit.
