Rooftop solar refers to photovoltaic (PV) systems installed on building rooftops — residential, commercial, industrial, or government — that convert sunlight into electricity using solar cells. Unlike utility-scale ground-mounted plants, RTS is a distributed energy resource (DER) generating power at or near the point of consumption.
Photo-voltaic = "Photo" (light) + "Volt" (electrical unit). PV cells are made of semiconductor material (typically silicon) that releases electrons when hit by photons.
| Term | Full Form / Meaning | UPSC Relevance |
|---|---|---|
| RTS | Rooftop Solar / Rooftop Solar System | Central topic term |
| PV | Photovoltaic — converts light to electricity | Tech definition MCQs |
| Net Metering | Surplus solar power fed to grid; consumer credited at retail rate | Policy distinction MCQs |
| Gross Metering | All solar power sold to grid at feed-in tariff; consumer buys all power from grid separately | Contrast with net metering |
| DISCOM | Distribution Company — state utility managing grid connection, net meter installation | Institutional role questions |
| CAPEX | Capital Expenditure model — consumer owns the system outright | Business model MCQs |
| OPEX / RESCO | Operational Expenditure / Renewable Energy Service Company — developer owns system, sells power via PPA | Business model MCQs |
| PPA | Power Purchase Agreement — contract between RESCO and consumer for fixed tariff over 15–25 years | OPEX model context |
| ALMM | Approved List of Models and Manufacturers — quality control list for solar modules/cells | Policy trap MCQs |
| DCR | Domestic Content Requirement — mandates use of Indian-made cells/modules | WTO dispute, Make in India linkage |
| GW / MW / kW | Gigawatt / Megawatt / Kilowatt (1 GW = 1000 MW = 10,00,000 kW) | Number confusion traps |
| RPO | Renewable Purchase Obligation — mandatory % of power DISCOMs must source from renewables | Regulatory compliance context |
| Type | Grid Connection | Key Feature | Used Where |
|---|---|---|---|
| Grid-Connected RTS | Yes | Feeds surplus to grid; net/gross metering applies | Urban homes, C&I, govt buildings |
| Off-Grid RTS | No | Battery storage; independent power supply | Rural/remote areas, telecom towers |
| Hybrid RTS | Both | Grid + battery backup; uninterrupted supply | Hospitals, data centres |
UPSC asks: "Which of the following correctly describes net metering?" — Key answer: net metering credits surplus solar power at retail rate and allows consumers to offset electricity bills. Gross metering pays a fixed feed-in tariff for all power generated. These are frequently confused.
JNNSM launch: 11 January 2010 · Target revision to 100 GW: 2015 by PM Modi · PM Surya Ghar launch: 13 February 2024 · 20.8 GW milestone: December 2025
UPSC loves asking about NAPCC — it has 8 missions; NSM (solar) is one. The others include National Mission for Enhanced Energy Efficiency (NMEEE), National Water Mission, etc. Know the correct mission name: Jawaharlal Nehru National Solar Mission — not simply "National Solar Mission" or "Modi Solar Mission."
| Sector | Share of 2025 Additions | Key Driver |
|---|---|---|
| Residential | ~76% | PM Surya Ghar subsidies & loans |
| Industrial (C&I) | ~18% | Electricity cost savings (CAPEX ROI 5–7 years) |
| Commercial | ~5% | Net metering credits, green branding |
| Government | ~1% | Mandatory rooftop targets for govt buildings |
| Rank | State | Cumulative Share | 2025 Additions Share |
|---|---|---|---|
| 1 | Gujarat | ~25% | 16% |
| 2 | Maharashtra | ~15% | 16% |
| 3 | Uttar Pradesh | ~8% | 15% |
| Top 10 states account for over 80% of cumulative RTS as of Dec 2025 | |||
By February 2026, MNRE data: Gujarat led at 6.67 GW, followed by Maharashtra (5.22 GW) and Rajasthan (2.07 GW) in absolute installed capacity.
| Indicator | Figure | Context |
|---|---|---|
| Total installed solar capacity (Dec 2025) | 136 GW | RTS = 20.8 GW of this |
| Total renewable capacity (Dec 2025) | ~262 GW | 51.5% of total installed capacity |
| Non-fossil power capacity crossed 50% | June 2025 | 5 years ahead of NDC target |
| Total installed power capacity | ~509 GW | As of Nov 2025 |
| RTS as % of total solar additions (2025) | >19% | Mercom India Research |
| India's overall RTS potential | ~796 GW | Only ~2.6% tapped so far |
| PM Surya Ghar subsidy disbursed (Dec 2025) | ₹13,464.6 crore | For 23.9 lakh households |
| PM Surya Ghar households installed (Dec 2025) | 23.9 lakh | Target: 1 crore by FY 2026–27 |
| India global solar rank (IRENA 2025) | 3rd | After China, USA |
| RTS target under NSM revised | 40 GW | Part of 100 GW solar target |
India's solar module manufacturing capacity grew from 38 GW (March 2024) to 74 GW (March 2025) — nearly doubling in one year under the PLI scheme. India transitioning from net importer to net exporter of solar PV.
| Parameter | Detail |
|---|---|
| Launch Date | 13 February 2024 (announced by PM Modi); also referenced as 29 February 2024 in budget context |
| Ministry | Ministry of New and Renewable Energy (MNRE) |
| Total Outlay | ₹75,021 crore (~US$ 9 billion) |
| Target | 1 crore (10 million) households by March 2027 |
| Rooftop Solar Capacity Target | 30 GW (residential sector) |
| Free Electricity Benefit | Up to 300 units/month for households with 3 kW system |
| Subsidy | Up to 40% CFA for systems ≤3 kW; 20% for 3–10 kW |
| Max Subsidy Amount | Up to ₹78,000 for systems up to 3 kW |
| Loans | Collateral-free at ~5.75% (Repo Rate + 0.50 bps) |
| Portal | pmsuryaghar.gov.in |
| Distinction | World's largest domestic rooftop solar initiative |
| Sunset Date | 2027 (PM Surya Ghar program reaches its sunset) |
| Progress (Dec 2025) | 23.9 lakh households; 7 GW capacity; ₹13,464.6 crore subsidy released |
| Scheme | Year | Ministry / Agency | Key Feature |
|---|---|---|---|
| JNNSM (NSM) | 2010 | MNRE | Parent mission; 100 GW solar target (40 GW rooftop) |
| RTS Phase I | 2010–2019 | MNRE / NVVN | First grid-connected RTS CFA; small residential subsidies |
| RTS Phase II | March 2019 | MNRE / DISCOMs | ₹11,814 crore CFA; 38 GW target; DISCOM incentivized |
| SRISTI | Ongoing | MNRE | Sustainable Rooftop Implementation for Solar Transfiguration of India; accelerates RTS adoption |
| SUPRABHA | Recent | MNRE | Sustainable Partnership for RTS Acceleration in Bharat; grassroots partnerships |
| PM Surya Ghar | Feb 2024 | MNRE | World's largest domestic RTS initiative; ₹75,021 crore; 1 crore HH target |
| PM-KUSUM | 2019 | MNRE | Solar pumps for farmers; Component C = grid-connected feeder solarisation |
| PLI (Solar PV) | 2021 | MNRE | Production Linked Incentive for high-efficiency solar PV modules; ₹4,500 crore; domestic manufacturing push |
| Solar Parks Scheme | Dec 2014 | MNRE / SECI | Target: 40 GW via large parks; ground-mounted, not rooftop |
| Body | Full Form | Role in RTS |
|---|---|---|
| MNRE | Ministry of New and Renewable Energy | Policy, CFA allocation, ALMM, scheme oversight |
| CERC | Central Electricity Regulatory Commission | Central-level tariff and regulatory orders |
| SERC | State Electricity Regulatory Commission | State-level net metering regulations, tariff |
| DISCOM | Distribution Company | Technical feasibility approval, net meter installation, grid sync |
| APTEL | Appellate Tribunal for Electricity | Appeals from CERC/SERC; SC final appeal |
| SECI | Solar Energy Corporation of India | Tenders, procurement, Solar Parks facilitation |
| NVVN | NTPC Vidyut Vyapar Nigam | NSM Phase I solar power procurement/trading |
| ISA | International Solar Alliance | India + France (COP21 2015); 124 member countries; "One Sun One World One Grid" |
UPSC frequently asks about DISCOM's limited role under PM Surya Ghar: DISCOM's role is restricted to (1) issuing technical feasibility approval, (2) installation of net meter, and (3) system inspection. DISCOMs do NOT own or finance the rooftop system.
| Feature | Net Metering | Gross Metering |
|---|---|---|
| Who uses | Consumers with RTS ≤10 kW (mandatory) | Consumers with RTS >10 kW (mandatory under 2022 rules) |
| Power flow | Surplus solar fed to grid; credited at retail rate against consumption | ALL solar power exported to grid at fixed feed-in tariff; consumer buys all power from grid |
| Benefit to consumer | Higher — offsets electricity bill at retail price | Lower — fixed lower feed-in tariff, separate purchase |
| Settlement | Monthly net (units consumed minus units exported) | Separate meters; two separate transactions |
| 2022 Rule | Mandatory for ≤10 kW systems | Mandatory for >10 kW loads (controversial — stalled larger RTS) |
| Karnataka innovation | Virtual Net Metering (VNM) & Group Net Metering (GNM) — credits across multiple sites | — |
Students confuse net metering = surplus credited at retail rate vs gross metering = ALL power exported at a lower feed-in tariff. The 2022 power ministry rules limiting net metering to ≤10 kW were controversial for stalling larger commercial RTS adoption.
| List | Coverage | Applicability |
|---|---|---|
| ALMM List-I | Solar PV Modules | Mandatory for all govt schemes, net metering & open access projects; ALMM List-I compliance mandatory from June 2026 |
| ALMM List-II | Solar PV Cells | Effective June 2026 for new projects; MNRE allows grandfathering for bids before Aug 31, 2025 |
| ALMM List-III | Solar Ingots & Wafers (NEW, 2026) | Effective June 2028; mandated when ≥3 independent manufacturers with 15 GW combined capacity available |
ALMM Order originally issued in 2019. Only ALMM-listed modules eligible for government projects, net metering, and open access projects under the Electricity Act, 2003 (Section 63).
| Policy | What It Does | Impact |
|---|---|---|
| DCR (Domestic Content Requirement) | Mandates use of Indian-made solar cells and modules in subsidized govt projects | WTO dispute (US challenged India's DCR); promotes Make in India; raises costs if domestic supply insufficient |
| BCD (Basic Customs Duty) | 25% BCD on solar PV cells; 40% BCD on solar PV modules (from April 2022) | Protects domestic manufacturers from Chinese imports; raises system prices short-term |
| PLI Scheme | Production Linked Incentive for high-efficiency solar PV modules | Module manufacturing capacity: 38 GW (March 2024) → 74 GW (March 2025); India moving to net exporter |
ALMM List-III for solar ingots and wafers (effective June 2028) is the newest ALMM development — added in 2026 to extend domestic sourcing to upstream solar value chain. UPSC Current Affairs 2026 question likely.
| Rank | Country | Approx. Capacity (End 2024) | Key Feature |
|---|---|---|---|
| 1 | China | ~887–1,100 GW | First country to cross 1,000 GW solar; 67% of global H1-2025 additions; 210 GW added in H1 2025 alone |
| 2 | USA | ~177–224 GW | Inflation Reduction Act (IRA) driving growth; residential solar threatened by "One Big Beautiful Bill" (July 2025) — ended federal tax credits |
| 3 | India | ~100–136 GW | Fastest-growing major solar market; 3rd globally (IRENA 2025); 4th in renewable energy capacity overall |
| 4 | Germany | ~100 GW | Passed 100 GW in 2025; leads globally in rooftop-driven solar; added ~16 GW in 2024 |
| 5 | Japan | ~90+ GW | Leader in floating solar, BIPV, high-efficiency rooftop; growth slowing |
India ranked 2nd in H1-2025 solar additions (24 GW, +49% YoY) behind only China. India ranked 4th globally in Renewable Energy installed capacity and 4th in Wind Power (IRENA RE Statistics 2025).
| Country | Rooftop Solar Highlight | Policy Driver |
|---|---|---|
| Germany | Global leader in rooftop-driven solar installations; 10 GW distributed solar added in 2024 | Feed-in tariffs, Energiewende policy |
| Australia | Highest rooftop solar per capita globally; 3.7 million homes with rooftop solar | Small-scale Technology Certificates (STCs) |
| China | Massive distributed solar growth; both utility and rooftop expanding | State investment, subsidy, domestic manufacturing |
| USA | Residential solar threatened by 2025 "One Big Beautiful Bill" removing federal tax credits and net metering mandates | IRA (2022) — now partially reversed |
| India | 20.8 GW cumulative (Dec 2025); 7.1 GW added in 2025 (+123% YoY); fastest growth globally in 2025 | PM Surya Ghar, ALMM, PLI, net metering |
| Brazil | Strong rooftop solar growth; distributed generation law (Lei 14.300/2022) enabled expansion | Net metering law + falling costs |
| Parameter | Detail |
|---|---|
| Founded | November 2015, COP21, Paris — jointly by India and France |
| HQ | Gurugram (Gurgaon), India — at National Institute of Solar Energy campus |
| Membership | 124 member countries (prospective: countries between Tropic of Cancer and Tropic of Capricorn, plus now extended) |
| Vision | "One Sun One World One Grid" (OSOWOG) — global solar interconnection |
| Goal | Mobilize $1 trillion for solar deployment by 2030; 1,000 GW solar capacity in member countries |
| Treaty status | International intergovernmental organisation; Framework Agreement entered into force October 2017 |
ISA HQ is in Gurugram, India — not New Delhi. ISA founding was at COP21 (Paris, 2015) — not COP26. Members originally: countries fully/partly between the Tropics of Cancer and Capricorn. Treaty entered into force: October 2017. These are high-frequency UPSC traps.
Global rooftop solar capacity grew by ~23% in 2024, adding nearly 220 GW worldwide — with major growth in Germany, Brazil, India, and Pakistan (REN21 Global Status Report 2025).
India's rooftop solar installations reached a cumulative 20.8 GW at end-December 2025, after adding a record 7.1 GW in 2025 — a 123% year-on-year increase over 3.2 GW in 2024. Residential consumers drove 76% of all 2025 additions, led primarily by PM Surya Ghar. Top states for 2025 additions: Maharashtra (16%), Gujarat (16%), Uttar Pradesh (15%).
The CAPEX model dominated with 85% of 2025 rooftop solar installations; OPEX/RESCO accounted for 15%. Rooftop solar accounted for over 19% of India's total solar installations in 2025. Rooftop solar tenders fell to 780 MW (Q4 2025) — a 46% quarter-on-quarter decline from 1.5 GW in Q3 2025.
As of 20 March 2026, more than 2.62 million rooftop solar systems deployed nationwide under PM Surya Ghar since the scheme launched in February 2024, benefiting approximately 3.24 million households (per Minister of State for MNRE Shripad Yesso Naik, Lok Sabha statement). Total rooftop solar installed under the scheme reached 9.56 GW by March 2026.
MNRE expanded the ALMM framework by introducing ALMM List-III for solar ingots and wafers — effective 1 June 2028. All net metering, open access, and Electricity Act Section 63 projects must mandatorily use ALMM-listed wafers from that date. List-III will be notified only when ≥3 independent manufacturers with combined capacity of 15 GW are operational.
India is expected to install about 42.5 GW of total solar capacity in 2026, including 8.5 GW of rooftop solar — a 72% increase year-on-year. Utility-scale solar target: 32.5 GW. CareEdge Ratings projected cumulative RTS to reach 25–30 GW by FY 2026–27.
India's cumulative solar capacity stood at 129 GW as of October 2025. Non-fossil electricity capacity crossed 259 GW, accounting for over 50% of total installed power capacity — a historic milestone. India achieved the 50% non-fossil capacity milestone in June 2025, five years ahead of its NDC target under the Paris Agreement.
The Parliamentary Standing Committee flagged slow progress of PM Surya Ghar: Muft Bijli Yojana — as of June 2025, only 16 lakh rooftop solar units (16% of 1-crore target) were installed, though the government claimed 24 lakh households benefited. ALMM List-II enforcement from June 2026 and rising DCR module prices are expected to increase system costs.
Expect MCQs on: (1) correct cumulative RTS figure (20.8 GW, Dec 2025), (2) PM Surya Ghar outlay (₹75,021 crore), (3) ALMM List-III coverage (ingots and wafers, effective 2028), (4) India's rank in solar globally (3rd, IRENA), (5) percentage milestone of non-fossil power (50%, June 2025).
| # | Statement | ✅/❌ | Reason / Correct Fact |
|---|---|---|---|
| 1 | "The Jawaharlal Nehru National Solar Mission was launched in 2015 by PM Modi." | ❌ | JNNSM launched 11 January 2010 by PM Manmohan Singh. PM Modi revised the target to 100 GW in 2015. |
| 2 | "Under net metering, ALL solar power generated is exported to the grid." | ❌ | Under net metering, only surplus power is fed to the grid after self-consumption. Under gross metering, ALL power is exported. |
| 3 | "International Solar Alliance was co-founded by India and France at COP26 in Glasgow." | ❌ | ISA was co-founded at COP21, Paris, November 2015 — not COP26 (Glasgow, 2021). |
| 4 | "ALMM List-III covers solar PV cells and mandates their use from June 2026." | ❌ | ALMM List-II covers solar PV cells (June 2026). ALMM List-III covers solar ingots and wafers, effective June 2028. |
| 5 | "Electricity is listed in the Union List of the Indian Constitution." | ❌ | Electricity is in the Concurrent List (Schedule VII, List III) — both Centre and States can legislate; Centre prevails in case of conflict. |
| 6 | "PM Surya Ghar: Muft Bijli Yojana provides up to 500 units free electricity per month." | ❌ | The scheme provides up to 300 units per month free for households with 3 kW systems. |
| 7 | "India's cumulative rooftop solar reached 20.8 GW at the end of December 2025." | ✅ | Correct — Mercom India Research data; 7.1 GW added in 2025 alone. |
| 8 | "Under the OPEX/RESCO model, the consumer owns the rooftop solar system." | ❌ | Under OPEX/RESCO, the developer (RESCO) owns the system. Consumer only signs a PPA and pays per unit. |
| 9 | "India achieved the milestone of 50% non-fossil power capacity 5 years ahead of its NDC target." | ✅ | Correct — India crossed the 50% non-fossil power capacity mark in June 2025; NDC target was for 2030. |
| 10 | "ISA Headquarters is located in New Delhi." | ❌ | ISA HQ is in Gurugram (Haryana), at the National Institute of Solar Energy campus. |
UPSC options often put 2010 and 2015 together. Remember: 2010 = JNNSM launch (Manmohan Singh) · 2015 = target revised to 100 GW (Modi) · 2024 = PM Surya Ghar. Never confuse the three milestones.
NSM rooftop target = 40 GW (part of 100 GW total). PM Surya Ghar target = 30 GW residential RTS (subset of 40 GW). PM Surya Ghar household target = 1 crore. These numbers are all different and frequently appear as MCQ distractors.
India is ranked 3rd in solar capacity globally (IRENA 2025) but 4th overall in renewable energy capacity and 4th in wind power. Do not mix these rankings. China = #1 (1,100 GW+), USA = #2 (~224 GW), India = #3.
List-I = Modules · List-II = Cells (June 2026) · List-III = Ingots & Wafers (June 2028). A common trap is to claim List-II = wafers or List-III = cells. The hierarchy goes from finished product (module) upstream to raw components (wafers).
Students often mark "Electricity" under the Union List. It is in the Concurrent List (Entry 38 of List III). Both Parliament and State Legislatures can make laws; in case of conflict, Parliament's law prevails (Article 254).
ISA was launched at COP21, Paris, 2015 — not COP26 (Glasgow, 2021). OSOWOG (One Sun One World One Grid) was unveiled at COP26 — a separate but related initiative. Do not conflate ISA founding with OSOWOG announcement.
| Number | What It Refers To |
|---|---|
| 20.8 GW | Cumulative RTS, December 2025 |
| 7.1 GW | RTS added in 2025 |
| 123% | YoY growth 2024→2025 |
| 9.56 GW | RTS under PM Surya Ghar by March 2026 |
| 40 GW | NSM rooftop solar target (part of 100 GW NSM) |
| 30 GW | PM Surya Ghar residential RTS target |
| 1 crore HH | PM Surya Ghar household target by FY 2026–27 |
| ₹75,021 crore | PM Surya Ghar total outlay |
| ₹78,000 | Max subsidy per household (up to 3 kW) |
| 300 units/month | Free electricity under PM Surya Ghar (3 kW system) |
| 796 GW | India's total RTS potential |
| 500 GW | India's non-fossil target by 2030 (Panchamrit/COP26) |
| 2070 | India's net-zero target year |
| June 2025 | India crossed 50% non-fossil power (5 yrs ahead of NDC) |
| 11 Jan 2010 | JNNSM launch date |
| 13 Feb 2024 | PM Surya Ghar launch date |