Sterling & Wilson Renewable Energy is the world’s largest solar engineering and construction specialist - a pure-play company that designs, builds, and maintains utility-scale solar power plants for governments and energy developers across 28 countries. Born from a five-decade-old engineering group and spun off in 2017 to focus entirely on renewables, it was later anchored by a 40% stake from Reliance Industries, aligning it with one of India’s most ambitious green-energy rollouts. Its recurring formula is simple: run a low-capital, made-to-order model from a cost-efficient Indian base, execute at gigawatt scale for the biggest clients, and lock in long-term maintenance contracts that pay steadily for years after the plant is built.
Business segments
Two engines that feed each other - a gigawatt-scale solar construction business that wins the project, and an annuity-like maintenance business that looks after it for decades.
1. Solar EPC: the gigawatt factory that builds the world’s solar plants
The company designs, procures, and constructs entire utility-scale solar power plants on a fixed-price basis - it is one of the only Indian players simultaneously building gigawatt-scale projects for NTPC, Adani Green, and Coal India.
- Turnkey builder, from dirt to grid - it takes a bare plot of land and delivers a fully operational solar plant, handling everything: design, engineering, buying the modules and steel, construction, testing, and connecting to the electricity grid. In FY26 alone, it commissioned roughly 4.5 GW AC of solar, which was about 15% of all utility-scale solar installed in India that year.
- Two ways to get paid - roughly 70% of new orders are full turnkey contracts where it supplies everything including the solar modules; the rest are Balance of System (BoS) contracts where the client buys the modules separately and the company does all the design and construction work. Turnkey jobs bring higher revenue but BoS jobs carry less commodity price risk, and the mix shifts depending on what clients want.
- The order book is the forward engine - it ended FY26 with a record unexecuted order book of about INR 11,813 crores, of which roughly 78% is domestic Indian projects and the rest is international, mostly in South Africa and the Middle East. Most projects take 12 to 18 months to build, so the order book converts to revenue quickly.
- Scale is the moat - the company has a global EPC portfolio of 27.3 GW across commissioned and under-construction projects, and it has built plants in punishing environments like the high-corrosive Rann of Kutch salt desert. It was ranked the world’s number-one solar EPC player by IHS Markit in 2019 and holds a Top Brand EPC 2025 recognition from EUPD Research.
- Not just panels on land - the EPC capability extends to floating solar plants installed on reservoirs and ponds (where it claims a first-mover advantage), hybrid solar-plus-wind projects, and large battery energy storage systems (BESS) with in-house design teams. In FY26 it won a 790 MWh pure battery storage project and its first wind EPC order as part of a hybrid project.
2. Operations & Maintenance: the long-tail annuity that pays for decades
Once a solar plant is built, the company stays on to run it - a 13.5 GW portfolio of long-term maintenance contracts that generate predictable, high-margin fees year after year.
- Caretaker for a continent’s worth of solar - the O&M portfolio hit 13.5 GW in FY26, up from 8.7 GW a year earlier, making the company what management calls “probably one of the largest third-party O&M players globally”. The portfolio has grown roughly sevenfold in eight years.
- Paid to keep the lights on - it earns annuity-style revenue from contracts that typically last more than five years, with gross margins expected to stabilise around 20%, far higher than the 10.5% consolidated gross margin in FY26. That creates a steady cash stream that smooths out the lumpy nature of construction revenue.
- One-third of the work comes from plants it didn’t build - about 32% of the O&M portfolio is third-party contracts, won by approaching plant owners when their original builder’s defect liability period expires and offering better service. The company actively hunts these opportunities, capitalising on dissatisfaction with incumbent operators.
- Technology as the differentiator - it runs a centralised monitoring platform that watches solar, wind, and battery assets on a single screen, and deploys drone thermography, robotic cleaning, and a NABL-certified mobile testing lab that can test modules on-site rather than shipping them to a facility. Its plants average 99.7% availability, beating the industry norm of 99.5%.
Group structure and partners
The company is a publicly listed pure-play renewable EPC with Reliance Industries as its 40% strategic anchor, a legacy promoter group holding 25.7%, and a network of 17 subsidiaries that give it boots on the ground across its target markets.
- Reliance is the strategic cornerstone - Reliance New Energy Limited acquired its 40% stake in FY22 through a combination of a preferential share issue, a purchase from the founding Shapoorji Pallonji promoters, and a public open offer. The company is in “active dialogue” with Reliance and has strategies to scale up quickly when Reliance’s multi-gigawatt solar manufacturing rollout accelerates.
- An indemnity backstop from the old guard - under the Reliance deal, the selling promoters signed an indemnity agreement covering old project liquidated damages, receivables, and tax disputes beyond INR 300 crore, and the company has successfully claimed and received payments under this arrangement.
- Subsidiaries are the international tentacles - the company operates through 17 subsidiaries, with key material units in Australia, South Africa, and Spain, and it incorporated new entities in Portugal and Romania in FY26 to chase the European renewable market. A US step-down subsidiary signed an MOU with the Nigerian government for a 961 MWp solar-plus-storage programme.
- A 50-50 joint venture for the next frontier - in June 2026, the company partnered with Hassan Allam Construction in a joint venture that won a USD 560 million contract to build a 1,000 MW solar plant with 600 MWh of battery storage in Egypt, covering full EPC and grid interconnection.