Question 1

kW (Kilowatt)

Accepted Answer

1 kW = 1000 watts. A 3 kW rooftop solar system can produce up to 3 kW of power at peak sun. Most Tamil Nadu homes use 2–5 kW systems.

Question 2

kWh (Unit / Kilowatt-hour)

Accepted Answer

What your EB bill measures. 1 kWh = 1 unit. In Trichy, 1 kW of solar generates about 4–4.5 units/day on average.

Question 3

Peak Sun Hours

Accepted Answer

Tamil Nadu averages 5–5.5 peak sun hours. Used to estimate generation: kW × peak sun hours = daily units.

Question 4

DC vs AC

Accepted Answer

Solar panels produce DC (direct current). The inverter converts it to AC (alternating current) which runs your appliances and EB grid.

Question 5

On-Grid Solar

Accepted Answer

Excess power is exported to TANGEDCO and adjusted in your bill via net metering. Cheapest option, but no power during grid outage. Best for daytime-heavy usage.

Question 6

Off-Grid Solar

Accepted Answer

Stores energy in batteries for night/outage use. Higher cost (battery is 30–40% of system price). Best for rural areas with frequent power cuts.

Question 7

Hybrid Solar

Accepted Answer

Best of both — uses solar, stores excess in battery, falls back to grid when needed. Ideal for homes with EB outages but wanting subsidy benefits.

Question 8

Net Metering

Accepted Answer

TANGEDCO installs a bidirectional meter. Units you export are credited against units you import. Your bill = net consumption only.

Question 9

DCR Panels (Domestic Content Requirement)

Accepted Answer

DCR (Domestic Content Requirement) panels are solar modules where BOTH the solar cells AND the module assembly are manufactured in India, using indigenous silicon wafers. Mandated by MNRE under the PM Surya Ghar Muft Bijli Yojana — only DCR panels qualify for the central government rooftop subsidy (up to ₹78,000). Brands: Waaree DCR, Premier Energies DCR, Adani DCR, Vikram DCR, Rayzon DCR. Pricing: ~₹4–6/Wp higher than Non-DCR. Comes with ALMM (Approved List of Models & Manufacturers) listing + BIS certification + 25-year linear performance warranty + 12-year product warranty. Mandatory for: all residential subsidy installs, all govt/PSU/MNRE-tendered projects, KUSUM agricultural solar pumps. Verify before buying: ask for ALMM Sl. No. and DCR certificate — fake DCR claims will get your subsidy rejected.

Question 10

Non-DCR Panels

Accepted Answer

Non-DCR panels use solar cells imported from China, Vietnam, Malaysia, or Taiwan — even if the final module is assembled in India. Cheaper by ₹4–8/Wp because Chinese cell manufacturing is at massive scale. NOT eligible for PM Surya Ghar residential subsidy or any MNRE-backed scheme. Best for: commercial/industrial (C&I) rooftops claiming accelerated depreciation instead of subsidy, captive power plants, export-oriented units, and budget-conscious off-grid installs. Quality can still be excellent — Tier-1 brands like Jinko, Trina, Longi, JA Solar dominate this segment globally with TOPCon and HJT tech. Carries the same 25-year performance + 12-year product warranty as DCR. Choose Non-DCR only if you don't need subsidy.

Question 11

ALMM Cell Mandate — 1 June 2026 (Non-DCR impact)

Accepted Answer

MNRE has confirmed (May 2026) that the ALMM List-II — Approved List of Solar Cells — comes into force from 1 June 2026 with NO blanket extension. This means the deadline of 31 May 2026 is the last day projects can be commissioned using imported (Chinese / Vietnamese / Malaysian) solar cells. From 1 June 2026 onwards, ALL net-metering rooftop projects, open-access projects, and government-tendered projects — including Non-DCR modules — must be built using solar cells manufactured in India and listed in ALMM List-II. Practical impact: (1) Non-DCR module prices will rise ₹2–4/Wp as imported-cell stock clears. (2) Modules already dispatched / invoiced before 31 May 2026 can still be installed under old rules if commissioned within the DISCOM grace window — check your state policy. (3) Pure-imported Non-DCR (cell + module both foreign) effectively exits the Indian rooftop market for grid-connected use. (4) Off-grid and pure captive installs without net-metering remain exempt. If you are planning a commercial Non-DCR install, lock the order and commissioning before 31 May 2026 to avoid the price hike.

Question 12

DCR vs Non-DCR — Cost Comparison

Accepted Answer

Example for 3 kW residential rooftop in Trichy: Non-DCR system ≈ ₹1,65,000 (no subsidy = ₹1,65,000 out-of-pocket). DCR system ≈ ₹1,95,000 minus ₹78,000 PM Surya Ghar subsidy = ₹1,17,000 out-of-pocket. DCR saves ~₹48,000 net despite higher sticker price. For commercial buyers: Non-DCR + 40% accelerated depreciation usually wins. Rule of thumb: residential homeowner → always DCR; commercial/MSME with tax liability → Non-DCR + AD.

Question 13

ALMM (Approved List of Models & Manufacturers)

Accepted Answer

ALMM is the MNRE-maintained list of solar module manufacturers and exact model numbers approved for use in government-subsidized and govt-procured projects. Only ALMM-listed DCR modules are accepted under PM Surya Ghar, KUSUM, CPSU, and state solar policy schemes. List is updated quarterly on mnre.gov.in. Always ask your installer for: (1) ALMM list serial number, (2) module model number printed on the back-sheet, (3) BIS certificate. If any are missing, the subsidy claim will fail at DISCOM inspection.

Question 14

How to verify DCR authenticity

Accepted Answer

(1) ALMM listing — search the manufacturer + model number on mnre.gov.in/almm-list. (2) DCR certificate — ask for the manufacturer's DCR self-certification on letterhead, valid for the financial year. (3) BIS marking — IS 14286 / IS/IEC 61215 / IS/IEC 61730 stamp on the module nameplate. (4) Serial number traceability — every panel has a unique serial; the installer must hand over the full serial list with the invoice for DISCOM inspection and warranty claims. SVN Safetech provides all four documents at handover for every DCR install.

Question 15

Solar Panel Efficiency

Accepted Answer

Panel efficiency is the percentage of sunlight energy that a solar panel converts into usable electricity. Standard panels today range from 19% to 23%. Higher efficiency means more power from the same roof area — critical when roof space is limited. A 20% efficient 550W panel produces the same output as a 19% efficient 550W panel, but higher-efficiency models typically use newer cell technology (TOPCon, HJT) that also degrades slower over 25 years.

Question 16

Mono PERC Panels (19–21%)

Accepted Answer

Passivated Emitter and Rear Cell (PERC) technology is the most common panel type installed in Tamil Nadu today. Efficiency: 19–21%. Cost: most affordable Tier-1 option. Works well in bright, direct sunlight. Downsides: slightly higher temperature coefficient (power drops more in extreme heat) and 0.55%/year degradation. Best for: budget-conscious homeowners with adequate roof space. Brands: Waaree PERC, Premier PERC, Trina PERC, Jinko PERC.

Question 17

TOPCon / N-Type Panels (22–23%+)

Accepted Answer

Tunnel Oxide Passivated Contact (TOPCon) uses N-Type silicon wafers instead of traditional P-Type. Efficiency: 22–23%+. Key advantages: (1) Lower temperature coefficient — power drops only ~0.30%/°C vs ~0.38%/°C for PERC, a big win in Trichy's 40°C summers. (2) Lower degradation: 0.40%/year vs 0.55%/year — after 25 years, a TOPCon panel retains ~90% output vs ~87% for PERC. (3) Better low-light performance — generates more during early morning, late evening, and cloudy monsoon days. Cost: ₹3–5/Wp premium over PERC. Best for: premium residential installs, limited roof space, or anyone maximizing lifetime output. Brands: Jinko Tiger Neo, Trina Vertex N, Longi Hi-MO 6, Waaree N-Type.

Question 18

Bifacial Panels

Accepted Answer

Bifacial panels are glass-on-glass modules with transparent backs that capture light reflected from the roof or ground. In optimal conditions (light-colored roof, elevated mounting, open ground), bifacial gain adds 10–25% extra yield on top of the front-side rating. Efficiency: same cell technology (PERC or TOPCon) plus bifacial architecture. Best for: ground-mounted systems, elevated structures, flat commercial roofs with white TPO coating, or carports. On typical Indian residential pitched roofs, the bifacial gain is smaller (5–10%) but still meaningful over 25 years.

Question 19

Half-Cut Cell Technology

Accepted Answer

Instead of 72 or 60 full-size cells, half-cut panels use 144 or 120 half-size cells. Benefits: (1) Lower electrical resistance inside the panel = 2–3% more output. (2) Better shade tolerance — if the bottom half is shaded, the top half still runs at full power because each half is wired separately. (3) Lower operating temperature = longer life. Nearly all modern 540W–600W panels sold in India today use half-cut architecture. It is now standard, not a premium feature.

Question 20

Temperature Coefficient

Accepted Answer

Solar panels are rated at 25°C, but on a Trichy rooftop in May, surface temperatures hit 60–70°C. The temperature coefficient tells you power loss per degree above 25°C. Example: a PERC panel at -0.38%/°C loses 0.38% × 35°C = 13.3% peak output on the hottest days. A TOPCon panel at -0.30%/°C loses only 10.5%. Over a year in Tamil Nadu's climate, this difference adds up to 3–5% more energy from TOPCon. When comparing panels, always check the temp coefficient — lower (less negative) is better.

Question 21

Efficiency vs Roof Space

Accepted Answer

A 3 kW system needs: ~8 panels of 400W (21% efficiency) vs ~6 panels of 550W (22% efficiency). The 550W system saves ~4 sq.m of roof area. For homes with limited south-facing roof (chimneys, water tanks, parapet walls), higher-efficiency panels let you squeeze more capacity into the available space. Rule of thumb: if your usable roof is under 25 sq.m, go for 540W+ high-efficiency panels. If roof space is generous (40+ sq.m), standard 400–445W PERC panels offer the best cost-per-watt.

Question 22

Degradation Rate

Accepted Answer

All solar panels lose a small amount of output every year due to UV exposure, thermal cycling, and humidity. Industry standard: 0.50–0.55%/year for PERC, 0.40%/year for TOPCon, and 0.30%/year for premium HJT (heterojunction). After 25 years: a PERC panel at 0.55% degradation retains ~87% of original output; TOPCon at 0.40% retains ~90%; HJT at 0.30% retains ~93%. Warranties reflect this — Tier-1 brands guarantee at least 80–85% output at year 25. Choosing lower degradation pays off most when your electricity tariff rises over time.

Question 23

Watt-Peak (Wp)

Accepted Answer

Wp (Watt-peak) is the panel's nameplate rating tested at 1000 W/m² sunlight intensity, 25°C cell temperature, and AM 1.5 spectrum. A 550Wp panel will produce ~550W at noon on a clear day in ideal conditions. In real Trichy conditions, actual output is 75–85% of Wp due to heat, dust, and wiring losses. When sizing a system, installers use Wp to calculate total capacity: 10 × 550Wp panels = 5.5 kW system. Daily generation estimate: 5.5 kW × 4.5 peak sun hours × 0.80 system efficiency = ~19.8 units/day.

Question 24

Solar Panel (Module)

Accepted Answer

Modern panels: Mono PERC, TOPCon (N-Type), or Bifacial. Tier-1 brands (Waaree, Premier, Rayzon) come with 25-year performance warranty.

Question 25

Inverter

Accepted Answer

Converts panel DC to home AC. Types: String inverter (cheapest), Micro-inverter (per-panel, best for shaded roofs), Hybrid inverter (battery + grid).

Question 26

Battery (LiFePO4 / Lithium)

Accepted Answer

Lithium iron phosphate (LiFePO4) is the modern standard — 10+ year life, deeper discharge, lighter than lead-acid. Used in off-grid and hybrid systems.

Question 27

Mounting Structure

Accepted Answer

Galvanized iron (GI) or aluminium frames designed for Tamil Nadu wind speeds (180+ km/h cyclone rated). Tilted 10–15° south-facing for max yield.

Question 28

ACDB / DCDB

Accepted Answer

AC Distribution Box & DC Distribution Box protect the system from surges, short circuits, and lightning. Mandatory for safe installation.

Question 29

Earthing & Lightning Arrestor

Accepted Answer

Copper earth pits + LA on the array. Critical in Tamil Nadu monsoon season — non-negotiable safety component.

Question 30

SolarEdge DC Optimizer

Accepted Answer

A small DC-DC converter mounted behind each panel. It performs MPPT (Maximum Power Point Tracking) per panel, so shading, dust, or a faulty module on one panel doesn't drag down the whole string. Pairs with a SolarEdge string inverter. Benefits: 5–25% higher yield on shaded/east-west roofs, panel-level monitoring (see each panel's output on app), safer rapid shutdown. Ideal for Tamil Nadu rooftops with chimneys, water tanks, or partial tree shade.

Question 31

Micro Inverter

Accepted Answer

Instead of one big string inverter, each panel gets its own micro-inverter (Enphase, Hoymiles, APsystems) that converts DC→AC right at the panel. No high-voltage DC on the roof = safer. Each panel works independently — shading on one doesn't affect others. Panel-level monitoring built-in. 25-year warranty (vs 5–10 for string inverters). Best for: complex/shaded roofs, future expansion, premium installs. Slightly higher upfront cost but better lifetime ROI.

Question 32

Lithium Battery (LiFePO4)

Accepted Answer

Lithium Iron Phosphate batteries (Luminous, Pylontech, BYD, Tesla Powerwall) are the gold standard for hybrid/off-grid solar. Vs old lead-acid: 10–15 year life (vs 3–5), 90%+ depth of discharge (vs 50%), 95% round-trip efficiency, 1/3 the weight, no maintenance, no fumes. Stores daytime solar for night use or backup during EB outage. Sizes: 2.4 kWh, 5 kWh, 10 kWh modular stacks. Cost: ₹60,000–₹80,000 per kWh installed. Smartphone monitoring + 10-year warranty standard.

Question 33

Zero Export Device (ZED)

Accepted Answer

An export limiter / anti-islanding controller that ensures 0 units flow back to TANGEDCO. Required when: (1) you don't have net metering approval yet, (2) commercial connections where export is restricted, (3) DG-set parallel operation. Uses a CT sensor at your meter — if solar generation > home load, it instantly throttles the inverter down. Avoids EB penalties and unauthorized export complaints. Mandatory on most commercial rooftops in Tamil Nadu without bidirectional meters.

Question 34

PM Surya Ghar Subsidy

Accepted Answer

Up to ₹78,000 subsidy for residential rooftop solar. Slab: ≤2 kW = ₹30,000/kW · 2–3 kW = +₹18,000/kW · ≥3 kW = capped at ₹78,000. Credited directly to your bank in ~30 days.

Question 35

MNRE Empanelment

Accepted Answer

Ministry of New & Renewable Energy maintains the official vendor list. Only empanelled installers (like SVN Safetech) can process PM Surya Ghar subsidy.

Question 36

Accelerated Depreciation

Accepted Answer

Businesses can claim 40% depreciation on solar assets in year 1 (Income Tax Act). Effectively reduces system cost by 25–30% for companies.

Question 37

Solar Loan / EMI

Accepted Answer

SBI, Canara, IOB & NBFCs offer solar loans at 9–11% interest, 5–10 year tenure. Monthly EMI usually less than your EB bill savings = solar pays for itself.

Feature	String Inverter	SolarEdge Optimizer	Micro-Inverter
Shading tolerance	Poor	Excellent	Best
Panel-level monitoring	No	Yes	Yes
DC voltage on roof	High (~600V)	Safe 1V (SafeDC)	None (AC only)
Warranty	5–10 yr	12 / 25 yr	25 yr
Cost	₹ Lowest	₹₹ Mid	₹₹₹ Premium
Best for	Unshaded simple roofs	Mixed/shaded roofs	Complex roofs, max reliability

Solar, explained in plain English

Solar Basics

System Types

DCR vs Non-DCR Panels

Panel Efficiency

Components

Latest Solar Technology

Subsidy & Finance

See the tech up close

SolarEdge DC Optimizer

Micro Inverters (Enphase)

String vs Optimizer vs Micro-Inverter

Lithium Iron (LiFePO₄) Battery Storage

Latest in Solar — what we install today

TOPCon N-Type Panels

Bifacial Panels

Half-Cut Cell Technology

LiFePO4 Lithium Storage

Hybrid Inverters with AI

IoT Cloud Monitoring

Rapid Shutdown Compliance

EV Charger Integration

Green Hydrogen Ready

Next steps

Estimate your savings

Is your home solar-ready?

Free site visit

Solar, explained in plain English

Solar Basics

kW (Kilowatt)System size / capacity.

kWh (Unit / Kilowatt-hour)Energy used or generated.

Peak Sun HoursEffective full-power sunlight per day.

DC vs ACPanels make DC, your home uses AC.

System Types

On-Grid SolarConnected to EB grid. No battery.

Off-Grid SolarBattery-backed. Works without grid.

Hybrid SolarGrid + battery backup.

Net MeteringSell extra power back to EB.

DCR vs Non-DCR Panels

DCR Panels (Domestic Content Requirement)Made-in-India cells + modules. Mandatory for subsidy.

Non-DCR PanelsImported cells, assembled in India or abroad. No subsidy.

ALMM Cell Mandate — 1 June 2026 (Non-DCR impact)From 1 June 2026, even Non-DCR projects must use ALMM-listed Indian solar cells.

DCR vs Non-DCR — Cost ComparisonNet cost after subsidy usually favors DCR for homes.

ALMM (Approved List of Models & Manufacturers)MNRE's official panel whitelist.

How to verify DCR authenticity4 checks before you pay.

Panel Efficiency

Solar Panel EfficiencyHow much sunlight a panel converts into electricity.

Mono PERC Panels (19–21%)The workhorse of Indian rooftop solar.

TOPCon / N-Type Panels (22–23%+)Next-gen cells — higher efficiency, lower heat loss.

Bifacial PanelsDouble-sided panels that harvest reflected light.

Half-Cut Cell TechnologyCells sliced in half for better performance.

Temperature CoefficientHow much power drops when panels get hot.

Efficiency vs Roof SpaceHigher efficiency = fewer panels for the same kW.

Degradation RateHow slowly panels lose power each year.

Watt-Peak (Wp)The maximum power a panel produces under lab conditions.

Components

Solar Panel (Module)The glass+silicon sheet on your roof.

InverterHeart of the system.

Battery (LiFePO4 / Lithium)Stores solar energy.

Mounting StructureHolds panels on your roof.

ACDB / DCDBSafety switchboards.

Earthing & Lightning ArrestorProtects from lightning strikes.

Latest Solar Technology

SolarEdge DC OptimizerPer-panel power booster.

Micro InverterOne tiny inverter per panel.

Lithium Battery (LiFePO4)Modern solar storage.

Zero Export Device (ZED)Stops solar from feeding the grid.

Subsidy & Finance

PM Surya Ghar SubsidyCentral govt rooftop solar scheme.

MNRE EmpanelmentGovt-approved installer list.

Accelerated DepreciationCommercial tax benefit.

Solar Loan / EMIZero down payment financing.

See the tech up close

SolarEdge DC Optimizer

Micro Inverters (Enphase)

String vs Optimizer vs Micro-Inverter

Lithium Iron (LiFePO4) Battery Storage

Latest in Solar — what we install today

TOPCon N-Type Panels

Bifacial Panels

Half-Cut Cell Technology

LiFePO4 Lithium Storage

Hybrid Inverters with AI

IoT Cloud Monitoring

Rapid Shutdown Compliance

EV Charger Integration

Green Hydrogen Ready

Next steps

Estimate your savings

Is your home solar-ready?

Free site visit

Lithium Iron (LiFePO₄) Battery Storage