Reference Guide — 35 Terms

Solar Energy Glossary

Understand key solar energy terms before installing a rooftop system. From AC Module to Zero Export — all explained in simple language.

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AC Module: A solar panel with a built-in micro inverter that directly outputs alternating current (AC), eliminating the need for a separate string inverter.
Battery Storage: Rechargeable batteries (lithium-ion or lead-acid) that store excess solar energy for use during nighttime or power outages.
Bi-facial Solar Panel: A solar panel that captures sunlight on both its front and rear surfaces, increasing energy generation by 5-30% compared to standard panels.
Charge Controller: A device that regulates the voltage and current from solar panels to batteries, preventing overcharging and extending battery life. Common types are PWM and MPPT.
DCR Panel: Domestic Content Requirement panel — a solar panel where both the solar cells and the module are manufactured in India. DCR panels are mandatory to qualify for PM Surya Ghar government subsidy. They cost slightly more than non-DCR panels but the subsidy savings far outweigh the premium.
DISCOM: Distribution Company — the state electricity utility responsible for distributing power to consumers. In UP, DISCOMs include MVVNL, PVVNL, DVVNL, PuVVNL, and KESCO.
EPC: Engineering, Procurement, and Construction — a turnkey project delivery model where one company handles the complete solar installation from design to commissioning.
Grid-Tied System: A solar system connected to the utility power grid. Excess solar power is exported to the grid, and grid power is used when solar production is insufficient.
Hybrid Inverter: An inverter that manages solar panels, battery storage, and grid connection simultaneously. Enables solar self-consumption with battery backup during outages.
Inverter: A device that converts direct current (DC) produced by solar panels into alternating current (AC) used by household appliances and the power grid.
kWh: Kilowatt-hour — a unit of energy equal to one kilowatt of power sustained for one hour. Used to measure electricity consumption and solar generation.
kWp: Kilowatt-peak — the maximum power output of a solar system under standard test conditions (STC). A 3kWp system generates approximately 360-450 units per month in UP.
Micro Inverter: A small inverter attached to each individual solar panel that converts DC to AC at the panel level, optimizing output even when some panels are shaded.
MNRE: Ministry of New and Renewable Energy — the Indian government ministry responsible for renewable energy policies, subsidies, and the PM Surya Ghar Yojana.
Module: Another term for a solar panel. A module consists of multiple solar cells connected together and enclosed in a protective frame with tempered glass.
Mono PERC: Monocrystalline Passivated Emitter and Rear Cell — a high-efficiency solar cell technology that uses a single crystal structure and rear-side passivation layer for 20-22% efficiency.
Mounting Structure: The aluminium or galvanized iron framework that secures solar panels to a rooftop or ground surface at the optimal tilt angle for maximum sunlight exposure.
Net Metering: A billing arrangement where excess solar electricity exported to the grid is credited against electricity consumed from the grid, reducing electricity bills.
Non-DCR Panel: A solar panel where the cells or module (or both) are manufactured outside India. Non-DCR panels are typically cheaper but do NOT qualify for PM Surya Ghar government subsidy. They are used in commercial installations where subsidy is not applicable.
Off-Grid System: A solar system not connected to the utility grid, relying entirely on solar panels and battery storage for power. Used in areas without reliable grid access.
On-Grid System: Same as a grid-tied system. Connected to the utility grid and eligible for net metering, making it the most cost-effective option for homes with reliable grid supply.
PM Surya Ghar: Pradhan Mantri Surya Ghar Muft Bijli Yojana — a central government scheme providing subsidies up to Rs 78,000 for residential rooftop solar installations up to 10kW.
Polycrystalline: A type of solar cell made from multiple silicon crystals. Less efficient (15-17%) than monocrystalline but more affordable. Identifiable by its blue speckled appearance.
Power Purchase Agreement: A contract between a solar developer and a consumer where the developer installs and maintains the solar system, and the consumer purchases the generated electricity at a fixed rate.
Rooftop Solar: Solar panels installed on the roof of a building. In India, residential rooftop solar (1-10kW) qualifies for PM Surya Ghar government subsidies.
Solar Cell: The basic unit of a solar panel that converts sunlight into electricity using the photovoltaic effect. Multiple cells are connected to form a solar module.
Solar Mounting Structure Types: The framework that holds solar panels in place. Two main types: (1) Galvanized Iron (GI) — affordable, strong, rust-resistant with zinc coating, lasts 15-20 years, heavier but ideal for most rooftops. (2) Aluminium — lightweight, corrosion-proof, lasts 25+ years, easier to install on weak roofs, but 30-40% costlier. For long-term residential use in UP, GI structures offer the best value; aluminium is preferred for coastal or high-humidity areas.
Solar Panel: A device made of interconnected solar cells that converts sunlight into direct current (DC) electricity. Standard residential panels produce 400-550 watts each.
Solar Panel Types: Three main types: (1) Monocrystalline (Mono PERC) — highest efficiency (20-22%), best for limited roof space, lasts 25-30 years, best long-term choice. (2) Polycrystalline — moderate efficiency (15-17%), more affordable, blue appearance, good budget option. (3) Thin-Film — lowest efficiency (10-13%), flexible and lightweight, used in commercial/industrial settings. For residential installations in UP, Mono PERC panels are recommended for maximum output and long-term savings.
Solar Subsidy: Financial assistance from central (MNRE) and state (UPNEDA) governments to reduce the cost of solar installation. Combined subsidy in UP can be up to Rs 1,08,000.
String Inverter: A centralized inverter that connects to multiple solar panels wired in series (a "string"). Cost-effective for installations without shading issues.
Tier-1 Solar Panel: A solar panel manufactured by a company listed in Bloomberg New Energy Finance (BNEF) Tier-1 ranking. Tier-1 manufacturers have large-scale production, strong financials, and proven track record. Brands like Tata, Adani, Waaree, Vikram, and Luminous are Indian Tier-1 manufacturers. Tier-1 panels are the best choice for long-term reliability — they maintain 80%+ output even after 25 years and come with bankable performance warranties.
UPNEDA: Uttar Pradesh New and Renewable Energy Development Agency — the state nodal agency that implements solar policies, manages vendor registration, and processes subsidy applications in UP.
Watt-peak (Wp): The rated power output of a single solar panel under standard test conditions. A 540Wp panel produces 540 watts at peak performance.
Zero Export: A configuration where the solar system is prevented from exporting excess power to the grid. Required in some commercial installations or where net metering is not available.