A zero-investment rooftop solar plant is the simplest way for a business to cut its power bill with solar. You don't buy anything or manage anything — Aran puts up the plant on your roof or land, runs it, and you just pay for the units it makes. This is also known as the OPEX or RESCO model.
In short
- What it is: Aran builds, owns and runs a solar plant on your roof or open land at your site. You invest nothing and pay an agreed rate per unit for the power you use. Also called the OPEX model, the RESCO model or an on-site solar PPA.
- Why on-site: power made and used on your own premises does not pay wheeling, cross-subsidy surcharge or additional surcharge, and does not need banking. Those are the charges that make buying power through the grid costly in Tamil Nadu since 2025.
- Who it suits: factories, mills, warehouses, hospitals and colleges with steady daytime power use and shade-free roof. Works on HT and LT connections.
- Roof needed: with today's panels, roughly 60–75 sq ft per kW on a metal-sheet roof and 80–100 sq ft per kW on a flat concrete roof. A 100 kW plant needs about 6,000–10,000 sq ft.
- Aran's edge: we make our own trackers, cleaning systems and mounting structures in Coimbatore. Where the site allows, a tracker makes up to 25% more power from the same space.
Keep your money in your business, not on your roof
A rooftop solar plant makes clear sense on paper — until you see the price tag. Buying one locks a big amount into something that isn't your core business, hands your team the job of running and cleaning it, and puts the risk of it under-performing on you. Many good solar plans stall for exactly this reason.
Zero-investment solar removes that blocker. Your money stays in what you do best, and you still get cleaner, usually cheaper, power from your own site.
How zero-investment solar works
Instead of buying a plant, you host one — and buy only the power:
- Aran builds and pays for the solar plant at your site — on your rooftop or on open land.
- Aran owns, runs, cleans, monitors and insures the plant for the whole agreement.
- You use the solar power it makes and pay an agreed rate per unit — usually below your current grid rate.
- No investment, no maintenance headache, and savings from day one.
Illustrative default values — request a site-specific quotation.
Rooftop solar in Tamil Nadu: why on-site often beats open access
A Tamil Nadu factory that buys third-party solar through the grid pays transmission and wheeling charges, a cross-subsidy surcharge (₹1.39 a unit for solar on an HT I connection) and loses up to about 6.6% of the units on the way. At an assumed ₹4.00 solar price, that comes to about ₹3 a unit on top of the generator's price. And under the 2025 rules it gets no banking for units it can't use at the time (TNERC Tariff Order No. 6 of 2025 and Green Energy Open Access Regulations 2025). Every charge, worked out →
A plant on your own roof skips all of that. The power goes straight into your machines. So for a factory with daytime load, the roof is usually the first place to look, and open access comes in for the load the roof can't cover. Grid-connected rooftop plants can still carry network charges set by TNERC; we put whatever applies into your numbers.
On an LT connection? Open access isn't allowed for LT in Tamil Nadu, so solar on your own premises is your route to cheaper power. We work across Coimbatore, Tiruppur, Erode, Karur, Salem, Chennai and Hosur, and across India.
How much roof do you need?
A quick check you can do with a tape measure. With today's 550 W-plus panels:
Count only shade-free roof: leave out skylights, vents, water tanks and the shadow of taller buildings. The full roof-sizing guide →
Illustrative default values — request a site-specific quotation. Our site survey confirms the usable area and the roof's strength.
Buying it yourself vs zero-investment — at a glance
Illustrative default values — request a site-specific quotation.
What Aran takes care of
Design & build
Full design, supply and installation of the plant at your site.
Running & upkeep
All operations and maintenance for the whole agreement — no in-house team needed.
Auto-cleaning
Aran's water-jet cleaning keeps the panels making full power, with water reused.
Monitoring
Round-the-clock tracking so power output stays on target.
Insurance
The plant is insured through the whole term — one less thing on your desk.
Performance
The deal is built on power delivered — Aran is paid on what the plant actually makes.
The tracker bonus — an even lower price per unit
Here's where Aran is different from a normal rooftop plant. Where the site allows, we use our solar tracker instead of a fixed mount. By turning the panels to follow the sun all day, the same space makes up to 25% more power.
Why that helps you
More power from the same roof or land means more of your electricity comes from lower-cost solar — which can mean a lower price per unit over the agreement, without you spending a rupee more.
Want to see how a tracker beats a fixed mount? See our solar tracker page →
Illustrative default values — request a site-specific quotation.
Two ways to work with us — which suits you?
Zero-investment — you buy only the power
You own nothing and invest nothing. Aran builds and runs the plant at your site; you just pay per unit for the solar power. Best for businesses that want cheaper, greener power with no ownership and no hassle.
Ask about zero-investment solarOwn the plant, share the tracker gain
Building your own plant but worried about the extra tracker cost? Keep the fixed-plant result as your floor, let Aran fund the tracker part, and share the extra power it makes — you can't end up worse off than a fixed plant.
See the solar trackerIs your site a fit?
Zero-investment solar works best when there's enough space and steady daytime power use to make the plant worthwhile. You're a strong fit if:
- You have shade-free roof space — or open land — for a solar plant.
- You have a steady daytime power use or sanctioned load.
- You'd rather put your money into your business than into a power plant.
- You want a steady, usually lower, price per unit without any upkeep worries.
Not sure? Share your details below and our team will check your site at no cost.
Common questions
What is a zero-investment rooftop solar plant?
A zero-investment rooftop solar plant — also called the OPEX or RESCO model — is built at your own site and owned and run by Aran. You put in no money and pay only for the power it makes, usually less than your current electricity rate.
How is this different from buying a solar plant yourself?
If you buy the plant, you pay the full cost up front and handle all the upkeep and risk. With zero-investment solar, you own nothing and pay only for the power you use, while Aran covers the cost, upkeep, cleaning, monitoring, insurance and performance.
Who looks after the plant?
Aran does — design, install, run, clean, monitor and insure it for the whole agreement. You run your business; we run the plant.
What do I need to qualify?
Enough shade-free roof or open land, a fairly steady daytime power use, and a stable site. Our team checks your site and your bills to size the plant.
How does the solar tracker lower my price per unit?
Where the site allows, Aran uses a solar tracker that follows the sun and makes up to 25% more power from the same space, which can mean a lower price per unit over the agreement. Figures are illustrative — please ask for a site-specific quote.
Does this work for rooftops and open land?
Yes. It works on factory, warehouse and building rooftops, and on open land at your site. Aran serves factories and businesses all over India.
How much roof space do I need for rooftop solar?
With today's 550 W-plus panels, roughly 60 to 75 sq ft per kW on a metal-sheet roof, and 80 to 100 sq ft per kW on a flat concrete roof where panels sit in tilted rows. So 100 kW needs about 6,000 to 10,000 sq ft of shade-free roof, and 500 kW about 30,000 to 50,000 sq ft. Our site survey confirms it.
Is rooftop solar better than open access in Tamil Nadu?
For daytime load, usually yes. Power used on your own premises avoids wheeling, cross-subsidy surcharge, additional surcharge and banking. Open access makes sense for the load your roof can't cover. Many factories do both: roof first, then open access or group captive for the rest.
Can an LT factory get zero-investment rooftop solar?
Yes. Rooftop solar works on LT and HT connections. In Tamil Nadu, LT connections can't take open access, so on-site solar is the main way for an LT factory to cut its power cost with solar.
Does my roof need to be checked first?
Yes. Our team checks the roof's structure, condition and shading before proposing a plant, and designs the mounting to suit it. Aran makes its own mounting structures.
Get a free zero-investment solar proposal
Tell us a little about your site and your power use — our team will check it and come back with a no-cost, illustrative proposal. No commitment.
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