# Solar Glossary

> Plain-English definitions of rooftop solar terms — kWp, net metering, DCR, MPPT, TOPCon, anti-islanding, sanctioned load and more.

Canonical: https://geniussolarservices.com/solar-glossary

- **ACDB** (AC distribution box): The enclosure on the AC side of a solar system containing the breaker, surge protection and isolator between the inverter and your home's wiring.
- **ALMM** (Approved List of Models and Manufacturers): MNRE's list of approved solar module models and manufacturers. Modules used in government-supported schemes are generally required to be on it.
- **Anti-islanding**: A safety function that shuts an on-grid inverter down when the grid fails, so it does not feed power into lines being repaired.
- **Bifacial module**: A solar panel that generates from both faces, capturing light reflected onto its back. Gains are highest on elevated structures over light-coloured roofs.
- **Bi-directional meter** (Net meter): An electricity meter that records both units imported from the grid and units exported to it. Required for net metering.
- **Busbar**: The thin metal strips printed on a solar cell that collect current. Modern cells use many thin busbars (multi-busbar) to reduce losses.
- **Bypass diode**: A diode in the module junction box that lets current flow around a shaded or damaged group of cells, limiting power loss and hot-spots.
- **Capacity utilisation factor (CUF)**: Actual annual generation divided by the maximum possible if the system ran at full rated power all year. Rooftop systems in Indore typically achieve around 16–17%.
- **CFA** (Central Financial Assistance): The central government subsidy for rooftop solar. Under PM Surya Ghar, homes receive up to ₹78,000.
- **DCDB** (DC distribution box): The enclosure on the DC side containing fuses, surge protection and an isolator between the panels and the inverter.
- **DCR** (Domestic Content Requirement): Solar modules made with cells manufactured in India. Mandatory for PM Surya Ghar subsidised systems.
- **DC:AC ratio**: Array DC capacity divided by inverter AC rating. A ratio slightly above 1 (e.g. 1.1) improves morning and evening output with minimal clipping.
- **Degradation**: The gradual loss of a module's output over time, typically 1–2% in year one and about 0.4–0.55% per year after that.
- **DISCOM**: Electricity distribution company. Indore is served by MP Paschim Kshetra Vidyut Vitaran Company Ltd (MP West Discom, MPPKVVCL).
- **Earthing**: Connecting metal parts and equipment to the ground so fault currents and surges have a safe path. Solar systems need earthing for frames, inverter and lightning arrester.
- **Efficiency (module)**: The share of sunlight hitting a panel that becomes electricity. Modern mono modules are around 20.5–23% efficient.
- **Elevated structure**: A raised solar mounting structure on tall columns that keeps the terrace usable underneath and lifts modules above shadows.
- **EVA** (Ethylene-vinyl acetate): The transparent encapsulant film that bonds and seals solar cells between the glass and backsheet. POE is an alternative with better moisture resistance.
- **Export**: Solar electricity sent from your premises to the grid when generation exceeds consumption.
- **Feasibility approval**: The DISCOM's technical approval that your connection can accept a rooftop solar system of the requested size.
- **Half-cut cells**: Solar cells cut in half so each carries half the current, reducing resistive losses and the impact of partial shading.
- **Hot-spot**: A cell that overheats because it is shaded or damaged while the rest of the module pushes current through it. Can permanently damage the module.
- **Hybrid inverter**: An inverter that manages solar, a battery and the grid together, providing backup during outages.
- **Import**: Electricity drawn from the grid into your premises.
- **Inverter**: The device that converts DC power from solar panels into AC power for your home and the grid.
- **Irradiance**: The power of sunlight reaching a surface, measured in watts per square metre (W/m²). Around 1,000 W/m² on a clear noon.
- **Junction box**: The sealed box on the back of a module containing bypass diodes and the output cables with MC4 connectors.
- **kW** (Kilowatt): A unit of power. Solar system size is stated in kW (or kWp) — the maximum it can produce under standard test conditions.
- **kWh** (Kilowatt-hour, 'unit'): A unit of energy — the 'units' on your electricity bill. A 1 kW system in Indore produces about 4 kWh a day.
- **kWp** (Kilowatt peak): The rated DC capacity of a solar array under standard test conditions (1,000 W/m², 25°C cells).
- **Lightning arrester**: A rooftop rod with its own earth connection that gives lightning a controlled path to ground, protecting the system and building.
- **Load enhancement**: An application to the DISCOM to increase your sanctioned load, sometimes needed before installing a larger solar system.
- **MC4 connector**: The standard weatherproof, locking connector used to join solar DC cables and modules.
- **MNRE** (Ministry of New and Renewable Energy): The Government of India ministry responsible for renewable energy, including rooftop solar schemes.
- **Monocrystalline**: Solar cells cut from a single silicon crystal. Higher efficiency and a uniform dark look; the standard for modern rooftops.
- **MPERC** (MP Electricity Regulatory Commission): The regulator that sets electricity tariffs and net-metering regulations in Madhya Pradesh.
- **MPPT** (Maximum power point tracking): The inverter function that continuously adjusts to extract the most power from the array as light and temperature change.
- **Net metering**: A billing arrangement in which exported solar units are offset against imported units, so you pay only for the net.
- **Off-grid system**: A solar system with batteries and no grid connection.
- **On-grid system** (Grid-tied): A solar system connected to the utility grid without batteries, using net metering. The most cost-effective type for most homes.
- **PERC** (Passivated Emitter and Rear Cell): A mono cell design that reflects unused light back through the cell, raising efficiency. The mainstream technology of the last decade.
- **Performance ratio (PR)**: Actual output divided by theoretical output from the sunlight received. Well-designed rooftop systems achieve about 0.75–0.82.
- **PM Surya Ghar: Muft Bijli Yojana**: The central government scheme (launched 2024) providing subsidy for residential rooftop solar — up to ₹78,000 per home and ₹18,000 per kW for housing societies.
- **Polycrystalline**: Solar cells made from multiple silicon crystals. Cheaper but less efficient; largely replaced by mono.
- **Sanctioned load**: The electrical load (kW) approved for your connection by the DISCOM. Net-metered solar capacity is generally linked to it.
- **SPD** (Surge protection device): A device in the DCDB/ACDB that diverts voltage surges (e.g. from lightning) away from the inverter.
- **String**: A group of solar modules connected in series to reach the inverter's operating voltage.
- **String inverter**: A central inverter that handles one or more strings of modules. The standard choice for Indian rooftops.
- **Temperature coefficient**: How much a module's power drops per °C rise in cell temperature, typically -0.30% to -0.40%/°C. Lower is better in hot climates.
- **Tilt angle**: The angle of the modules from horizontal. Around 15–23° suits Indore.
- **TOPCon** (Tunnel Oxide Passivated Contact): An n-type cell technology with higher efficiency, lower degradation and better heat tolerance than PERC.
- **Yield (specific)**: Annual energy produced per kWp installed. About 1,400–1,550 kWh/kWp in Indore depending on site and losses.

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**Genius Solar Services** · G-1, Swarna Palace, Plot No. 1108, Scheme No. 114, Part 1, Vijay Nagar, Near MP Gramin Bank, Indore, Madhya Pradesh 452010 · Phone +91 98267 12299, +91 78288 12299, 0731 400 4499 · geniussolarservices@gmail.com · Mon – Sat · 10:00 am – 7:00 pm
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