Solar Terminology Dictionary: ALMM, DCR & CFA Explained

Navigating the Indian solar market requires understanding a highly specific set of acronyms and regulatory terms. This glossary provides simple, accurate definitions.

ALMM (Approved List of Models and Manufacturers)

A list maintained by the Ministry of New and Renewable Energy (MNRE) of verified solar panel models and their manufacturers. Panels used in subsidized projects must be ALMM-compliant to ensure quality and reliability.

CFA (Central Financial Assistance)

The official term for the central government subsidy provided to residential solar consumers. Under the PM Surya Ghar scheme, this is currently capped at ₹78,000 for systems 3kW and above.

DCR (Domestic Content Requirement)

A mandate requiring that solar panels are manufactured in India using Indian-made solar cells. Compliance is strictly required to claim the PM Surya Ghar CFA.

Net Metering

A bidirectional billing mechanism. Excess solar power exported to the grid is subtracted 1:1 from the power imported from the grid at night. You are billed only for the net difference.

Net Billing (Gross Metering)

A billing mechanism where exported solar power is credited at a fixed, lower rate (Feed-in Tariff), while imported power is billed at standard high retail rates. In many states, this applies to systems over 10kW.

CEIG (Chief Electrical Inspector to Government)

A state-level regulatory body that must inspect and approve the safety of larger electrical installations (typically above 10kW) before they can be synchronized with the grid.

Advanced Engineering & Regulatory Terminology

ALMM (Approved List of Models and Manufacturers)

An official regulatory roster maintained by the Ministry of New and Renewable Energy (MNRE). Only solar panels listed on ALMM are legally eligible for grid-connected projects and PM Surya Ghar government subsidies.

DCR (Domestic Content Requirement)

A mandatory government policy mandating that both the solar photovoltaic cells and the solar modules must be manufactured inside India to qualify for central financial assistance.

CUF (Capacity Utilization Factor)

The ratio of the actual annual electricity generated by a solar plant compared to the maximum theoretical output if the plant operated at 100% rated capacity 24 hours a day for 365 days. Rooftop solar plants in India typically achieve a CUF of 17% to 21%.

PR (Performance Ratio)

The percentage metric measuring the actual relationship between real AC energy delivered to the building compared to the nominal DC capacity under prevailing solar irradiation. High-grade grid-tied rooftop systems achieve a PR between 75% and 82%.

Albedo Effect

The fraction of solar radiation reflected from the ground or roof surface. Bifacial solar panels take advantage of high-albedo surfaces (such as white reflective terrace paint or light concrete) to generate up to 20% additional power from their rear glass face.

Anti-Islanding Protection

A mandatory safety mechanism built into all grid-tied solar inverters that disconnects the solar plant from the grid within milliseconds if utility grid power fails, preventing dangerous electrocution of utility linemen.

Essential System Sizing & Performance Terms

Kilowatt (kW) vs. Kilowatt-Hour (kWh)

Think of Kilowatt (kW) as your car's speedometer (how fast power is generated at any given second) and Kilowatt-Hour (kWh) as your car's odometer (how much total electrical energy was generated over time). A 3 kW solar system running at full capacity for 4 hours produces 12 kWh (units) of electricity.

VOC (Open-Circuit Voltage) & ISC (Short-Circuit Current)

VOC is the maximum voltage a solar panel produces when disconnected from any load (open circuit). ISC is the maximum current that flows when the positive and negative output leads are shorted together. Inverter designers use VOC to ensure the total string voltage never exceeds the inverter's maximum input voltage limit on cold, sunny mornings.

VMP (Voltage at Maximum Power) & IMP (Current at Maximum Power)

The specific operating voltage (VMP) and current (IMP) at which a solar panel generates its highest possible wattage output. Inverters use Maximum Power Point Tracking (MPPT) microprocessors to continuously tune voltage and current to operate precisely at VMP and IMP throughout changing sunlight conditions.

Temperature Coefficient of Pmax

Solar panels are tested at Standard Test Conditions (STC) of 25°C. For every degree Celsius the panel temperature rises above 25°C, its electrical power output drops by a tiny percentage (typically -0.30% to -0.38%/°C). Modern TOPCon and HJT panels feature lower temperature coefficients, producing more electricity on blazing hot 45°C Indian summer afternoons than older Polycrystalline modules.

Bypass Diodes

Protective semiconductor diodes installed inside the module junction box. When one cell or a section of a panel is shaded by a bird dropping or tree branch, current cannot flow through it. The bypass diode opens a bypass path around that shaded section, preventing the shaded cell from overheating into a dangerous hotspot and allowing the rest of the string to keep generating electricity.

Inverter Clipping (Saturation)

When a solar array produces more DC power than the inverter's rated maximum AC output capacity, the inverter clips the peak power curve to its maximum allowable wattage. Sizing the DC array slightly larger than the inverter (e.g. 1.15 to 1.25 DC-to-AC ratio) is standard industry engineering practice, as it delivers more total kilowatt-hours during early morning, late afternoon, and cloudy hours without damaging the inverter.

Degradation Rate & Linear Performance Warranty

All silicon solar panels gradually lose a fraction of their generating capacity over time due to light-induced degradation (LID) and environmental exposure. Quality tier-1 solar panels experience less than 2% degradation in Year 1 and under 0.55% per year thereafter, guaranteeing at least 80% to 87% of initial rated power output after 25 years.

Sanctioned Connected Load

The maximum electrical power capacity in kilowatts (kW) that your utility company permits your property to draw from the grid, as stated on your monthly electricity bill. Under state net metering regulations, your solar installation capacity is generally capped at 100% of your sanctioned connected load (or up to 150% in certain progressive states).

Banking Period & Settlement Cycle

The designated regulatory timeframe—typically a 12-month cycle from April 1 to March 31—during which excess solar units exported to the grid are banked and can be drawn upon to offset higher electricity bills in other months. At the end of the settlement cycle, any unconsumed surplus units are settled and paid to the homeowner by the DISCOM at predetermined Average Power Purchase Cost (APPC) rates.