Solar Glossary: Rooftop Solar Terms Explained

Written by the SolarSpot team · Reviewed by Amaan Hussain, Founder · Updated 31 October 2026 · 29 terms

A

AMC

An annual maintenance contract (AMC) is a paid service agreement that covers scheduled maintenance of a solar plant, usually for commercial and industrial systems.

B

Bifacial solar panel

A bifacial solar panel generates electricity from sunlight on its front and from light reflected onto its back, which adds extra generation on an elevated, open frame.

C

Commissioning certificate

A commissioning certificate confirms that a rooftop solar system has been installed, inspected, and connected. Under PM Surya Ghar, it is uploaded on the national portal to start the subsidy claim.

D

Days of autonomy

Days of autonomy is the number of days an off-grid solar system can run on its batteries alone, without sunshine. It sets the size of the battery bank.

DCR panel

A DCR (domestic content requirement) panel is a solar module made with cells manufactured in India. PM Surya Ghar subsidy projects must use approved DCR panels.

DISCOM

A DISCOM is an electricity distribution company. It approves rooftop solar connections, inspects systems, installs net meters, and bills consumers.

E

Earthing

Earthing connects the metal parts of a solar system to the ground through an earth pit, so fault currents and lightning surges flow safely away.

Elevated solar structure

An elevated solar structure is a steel frame that raises rooftop panels above the roof like a canopy, clearing shade from tanks and parapets and keeping the terrace usable.

EPC

EPC stands for engineering, procurement, and construction. An EPC company designs, sources, builds, and commissions a complete solar plant as a single point of contact.

H

HDGI steel

HDGI (hot-dip galvanized iron) steel is steel coated with zinc by dipping it in molten zinc. The SolarSpot OCTASHIELD structure uses 3 mm HDGI steel with an 80 to 120 micron coating.

Hot-dip galvanizing

Hot-dip galvanizing is a rust-protection process in which finished steel is dipped in molten zinc, bonding a protective coating to every surface.

Hybrid inverter

A hybrid inverter manages solar panels, a battery, and the grid together. It powers backup loads from the battery during a power cut and exports surplus power through net metering.

Hybrid solar system

A hybrid solar system connects to the grid and also stores energy in a battery, so it saves through net metering and keeps essential loads running during power cuts.

I

Inverter

An inverter converts the DC electricity produced by solar panels into AC electricity that home and business appliances use.

K

kW (kilowatt)

A kilowatt (kW) measures the rated power of a solar system. SolarSpot installs home systems of 3 kW and above.

L

Lightning arrester

A lightning arrester is a rod mounted above a solar structure that intercepts lightning and carries the strike through a conductor to an earth pit.

M

MNRE

MNRE is the Ministry of New and Renewable Energy, the Government of India ministry responsible for solar and other renewable energy programmes.

MPPT charge controller

An MPPT (maximum power point tracking) charge controller draws the most power from solar panels and charges batteries safely in an off-grid system.

N

N-type solar cell

An N-type solar cell is made on a silicon wafer doped to carry negative charge. N-type cells, such as TOPCon cells, lose less energy than older P-type cells.

Net meter

A net meter is a bidirectional electricity meter that records units imported from the grid and units exported by a rooftop solar system.

Net metering

Net metering is a billing method in which a consumer pays only for net units, which are the units imported from the grid minus the units exported by their rooftop solar system.

O

OCTASHIELD

OCTASHIELD is the SolarSpot elevated solar structure, built with tapered octagonal legs of 3 mm HDGI steel, top-hat purlins, and a 180 km/h wind rating.

Off-grid solar system

An off-grid solar system runs only on solar panels and batteries, with no connection to the utility grid. It suits remote sites with no dependable grid supply.

On-grid solar system

An on-grid solar system connects to the utility grid through a net meter and has no battery. It gives the lowest electricity bills and switches off during power cuts for safety.

P

PM Surya Ghar Muft Bijli Yojana

PM Surya Ghar Muft Bijli Yojana is a Government of India scheme that subsidizes rooftop solar for homes, with a central subsidy of up to ₹78,000 for systems of 3 kW or more.

S

Sanctioned load

Sanctioned load is the maximum electrical load your DISCOM has approved for your connection. A rooftop solar system cannot exceed it without a load increase.

T

Top-hat purlin

A top-hat purlin is a horizontal structure member with a closed, hat-shaped profile that holds a row of solar panels rigidly on the frame.

TOPCon

TOPCon (tunnel oxide passivated contact) is an N-type solar cell design with a thin oxide layer on the back that reduces energy losses and raises panel efficiency.

U

Unit (kWh)

A unit is one kilowatt-hour (kWh) of electricity, the amount your electricity bill counts. A 3 kW rooftop system generates about 450 units a month.