Buy it or pay per unit?
CAPEX or OPEX: how to decide
Owning the plant gives the lowest cost per unit over its life and lets you claim accelerated depreciation, but you fund the whole system upfront. Published analysis puts post-depreciation payback at 3.5–4 years for tax-paying companies on owned property with a horizon of eight years or more.
RESCO suits buyers who are short of capital, lease their premises, or can’t use the tax benefit, such as hospitals and schools. You pay only for units generated, savings start in month one, and the spend stays an operating expense.
What this calculator assumes
Your grid tariff stays flat for the whole term, so the savings shown are conservative if tariffs rise. The tax saving counts only the 40% first-year depreciation claim. Roof area uses 80–100 sq ft per kW; panels and structure also add about 30 kg/m² of dead load, so get a structural check before signing.
When rooftop solar makes sense for a business
- You own the building or have a lease long enough to cover the payback period.
- The roof is strong, shade-free and will not need major repairs soon.
- Most of your power is used in daylight, so you use the solar units yourself instead of exporting them.
- Your grid price is ₹7 a unit or more, which is typical for commercial and industrial connections.
If you lease the building or don’t want capital tied up, the pay-per-unit (RESCO) route still gives you rooftop power with no upfront cost.
Frequently asked questions
How much does C&I rooftop solar cost per kW in 2026?
Published 2026 guides put turnkey C&I rooftop plants at roughly ₹35,000–45,000 per kW, and ₹38–50 per watt-peak for projects above 100 kW, depending on size, roof type and structure.
What does a RESCO or OPEX rooftop contract cost?
A developer owns and runs the plant on your roof and sells you the power under a 15–25 year PPA. Published 2026 tariffs range from about ₹4.0 to ₹5.5 per kWh.
How much roof space do I need?
Plan for about 80–100 sq ft of shadow-free roof per kW. A 100 kW plant needs roughly 8,000–10,000 sq ft.
Can I claim accelerated depreciation?
Under the CAPEX model a business can claim 40% depreciation in the first year, which reduces its tax bill. RESCO buyers don’t own the asset, so they can’t claim it.
The formulas and sources behind this calculator are on how we calculate.