MAHLE Chennai Rooftop Solar: ₹17 Lakh Saved With Zero Capex
Published Nov 5, 2026
MAHLE's 500 kWp zero-capex rooftop solar plant in Chengalpattu, Tamil Nadu delivered 7.72 lakh units and ₹17.4 lakh in savings in 12 months.
SustVest built, owns and runs a 500.5 kWp rooftop solar plant for MAHLE ANAND Filter Systems at its filtration systems factory in Thenur Village, Chengalpattu, near Chennai, Tamil Nadu. MAHLE spent no capital. From October 2025 to September 2026 the plant delivered 7.72 lakh units of solar power and saved MAHLE ₹17.4 lakh, based on actual billed units.
At a glance
Client | MAHLE ANAND Filter Systems Pvt. Ltd. |
Industry | Auto components (filtration systems) |
Location | Thenur Village, Chengalpattu, Tamil Nadu |
Capacity | 500.5 kWp DC / 400 kW AC rooftop solar |
Model | OPEX (RESCO), zero capex |
Generating since | February 2025 |
Generation (last 12 months) | 7,72,122 kWh, or 1,543 kWh per kWp |
Savings (last 12 months) | ₹17.4 lakh, net of solar payments |
CO₂ avoided (last 12 months) | 5,49,519 kg, equal to about 25,242 trees |
The problem: rising HT power tariffs in Tamil Nadu
MAHLE's Chengalpattu plant buys power on TANGEDCO's high tension (HT) industrial tariff, where the energy charge alone is ₹7.50 per unit for 2025-26, before time-of-day peak surcharges, demand charges and electricity tax.
Tamil Nadu raised power tariffs in July 2023, July 2024 and July 2025, so grid power is expected to keep getting more expensive.
Why it needed a different approach
MAHLE already ran a SustVest plant at its Parwanoo, Himachal Pradesh factory, so the zero-capex model was proven. The open question at Chengalpattu was metering: an older solar plant already fed the same meter. SustVest solved it with a monthly joint meter reading, signed by both teams, that nets out the older plant's output, so MAHLE pays only for units from the SustVest plant.
What SustVest built
Capacity: 500.5 kWp DC / 400 kW AC rooftop solar plant
Timeline: TANGEDCO grid tie-up approval on 30 October 2024; supply and billing from February 2025
Hardware: 910 EVVO 550 Wp mono PERC solar modules and four EVVO 100 kW string inverters
Metering: shares a meter with an older on-site solar plant, so units are settled every month by joint meter reading
See how the OPEX solar model lets factories go solar with zero investment.
Results
Savings: ₹17.4 lakh net in the last 12 months (October 2025 to September 2026); ₹26.2 lakh net since February 2025
Generation: 7,72,122 kWh in the last 12 months, 1,543 kWh per kWp (4.2 units per kWp per day); 11,64,652 kWh since February 2025
CO₂ avoided: 5,49,519 kg in the last 12 months; 8,28,883 kg since February 2025 (at the CEA grid factor of 0.7117 kg per kWh)
Repeat business: MAHLE also runs SustVest plants at Parwanoo, Himachal Pradesh, including a 100 kWp extension that started supply on 25 August 2026
Monthly solar generation, last 12 months
Month | Units (kWh) |
October 2025 | 52,260 |
November 2025 | 61,155 |
December 2025 | 48,166 |
January 2026 | 51,010 |
February 2026 | 64,570 |
March 2026 | 80,886 |
April 2026 | 77,383 |
May 2026 | 61,400 |
June 2026 | 64,675 |
July 2026 | 69,627 |
August 2026 | 72,747 |
September 2026 | 68,244 |
Total | 7,72,122 |
What we learned: output follows the monsoon
In the last 12 months the best month (March 2026, 80,886 kWh) produced 68% more than the weakest (December 2025, 48,166 kWh), when the northeast monsoon brings cloud cover to Chennai. Monthly savings move the same way, so the annual figure is the one to plan around.
Frequently asked questions
1. How much does a 500 kWp rooftop solar plant save an auto components factory in Tamil Nadu?
About ₹17.4 lakh a year at MAHLE's Chengalpattu plant, based on actual billed units. The 500.5 kWp plant delivered 7.72 lakh units from October 2025 to September 2026, supplied under SustVest's OPEX model at a fixed tariff below the ₹7.50 per unit TANGEDCO HT energy charge. MAHLE spent no capital.
2. How much does rooftop solar generate per kW in Chennai?
About 1,540 units per kWp a year, or 4.2 units per kWp a day, based on MAHLE's 500.5 kWp plant at Chengalpattu from October 2025 to September 2026. Output peaks in March and April and dips between October and January, during the northeast monsoon.
3. Can a factory add rooftop solar if it already has a solar plant?
Yes. At MAHLE's Chengalpattu site, an older solar plant already fed the same meter. SustVest and MAHLE sign a joint meter reading every month that nets out the older plant's output, so MAHLE is billed only for units from the new SustVest plant.
4. What is zero investment (OPEX) rooftop solar?
Under SustVest's OPEX (RESCO) model, SustVest funds, builds, owns and maintains the rooftop solar plant. The factory pays only for the solar units it uses, at a fixed per-unit tariff below its grid rate. Savings start from the first month, with no capital spent by the factory.
See what your factory roof could save
SustVest builds, owns and runs rooftop solar plants for factories across 13 Indian states, with zero upfront investment.