Solar ROI + EV Break-Even Calculator

Monthly Household Units (pre-EV) 320 units

50800 units/mo

Daily EV Commute 40 km/day

10 km120 km

EV Model — Wh/km

Rooftop Solar System Size

Total subsidy (Central + TN TEDA) ₹78,000

TN Govt. 200 Free Units

Scheme active — deducted from gross

Petrol ₹/L · Chennai

₹ /L

Solar Break-Even

—

months to recover investment

TANGEDCO SLAB (BI-MONTHLY) —

Free₹1.50₹2₹3 ₹4₹5.50₹6.60₹7.60

Without Solar

₹—

per month

With Solar

₹—

per month

Monthly Saving

₹—

electricity bill reduction per month

Net Investment

₹—

after subsidy

Solar Output

— units

per month

5-Year Net Saving

₹—

Annual Return est.

—%

Cost Per Kilometre

EV (with solar)

₹—/km

Petrol

₹—/km

EV costs —% less per km with solar

EV cost/km without solar ₹—/km

Assumes 16.5 km/L petrol car · Chennai petrol ₹100.84/L · AC charging efficiency 87%

5-Year Cumulative Projection

Net saving vs. solar investment outlay

Investment

Cumulative saving

Break-even yr

Detailed Calculation Breakdown

Ready for the full TCO calculation?

Purchase price, insurance, maintenance, and resale value.

Sources: TANGEDCO Tariff 2026 (8-slab bi-monthly) · PM Surya Ghar Phase II (Jan 2026) · TN TEDA 2026 · Chennai petrol ₹100.84/L · May 2026