Solar LCOE and Payback Calculator

Enter your capacity, state and current tariff and the calculator returns annual generation, levelised cost of energy, simple and discounted payback, project IRR, 25-year savings and the carbon abated — with the year-by-year cash flow behind it.

What the calculator asks for

• System capacity in kWp
• State, which sets the peak sun hours used for the yield
• Mounting type — rooftop, ground mount, single-axis tracker or floating
• Capex per Wp and any capital subsidy
• Your current tariff per kWh and the escalation you expect
• O&M cost, module degradation, discount rate and project life
• What share of generation is consumed on site rather than exported

How LCOE is calculated here

Levelised cost of energy is the net present value of all project costs divided by the net present value of all the energy produced — not total cost divided by total units. Both sides are discounted, because a rupee saved in year 20 is not worth a rupee spent today and a unit generated in year 20 is not worth a unit generated now. Discounting only the costs and not the energy understates LCOE by 25-40%, which is the single most common error in solar business cases.

Generation declines every year. A one-off first-year light-induced drop of about 2% is applied, then the linear degradation rate compounds across the project life, so a plant at 0.6% a year delivers roughly 85% of year-one output by year 25.

Yield assumptions by state and mounting

Peak sun hours range from about 5.8 a day in Ladakh and 5.6 in Rajasthan down to 4.3 in Assam and 4.7 in West Bengal. Performance ratio — the share of available irradiation the plant actually converts after temperature, soiling, cable and inverter losses — is taken as 78% for rooftop, 80% for fixed-tilt ground mount, 81% for trackers and 83% for floating solar, where water cooling keeps the modules several degrees cooler.

Single-axis trackers add roughly 16% to annual yield by following the sun, which is why utility plants use them and why they rarely pay below about 1 MWp.

Self-consumption changes everything

Rooftop solar is worth what it displaces. A unit consumed on site saves your full commercial tariff of ₹7-11; a unit exported earns a feed-in rate often around a third of that. That is why an array sized to your measured daytime baseline usually pays back faster than a larger one sized to your roof — and why the calculator flags any case where self-consumption falls below 70%.

Before you commit capital

These figures are a screening model, not a bankable yield assessment. A site-specific simulation against measured irradiation, a structural check on the roof or soil, and the applicable DISCOM, open access and ALMM rules will all move the result. Send your load profile and tariff to Stancor Solar Power and our engineering team will model the project properly.

For availability, a yield study and DPR and a capacity and yield response, contact Stancor Solar Power.