Solar Glossary: Every Solar Term Explained
From kWh to SEAI grants, solar energy comes with a lot of jargon. This glossary explains 73+ solar terms in plain English, with Irish-specific context for every definition.
Quick Answer
This glossary covers all the key solar energy terms you will encounter when researching solar panels for your home in Ireland — from technical terms like kWp and MPPT to financial concepts like payback period and SEAI grants.
Last updated March 2026
Fact-checked by John Rooney, Solar Energy Editor. Editorial policy
Technology
Solar PV
Solar photovoltaic (PV) technology converts sunlight directly into electricity using semiconductor cells.
Photovoltaic Cell
The smallest unit of a solar panel that converts sunlight into electricity through the photovoltaic effect.
Solar Thermal
A system that uses sunlight to heat water directly, as opposed to generating electricity.
Monocrystalline
The most efficient type of silicon solar cell, made from a single continuous crystal structure.
Polycrystalline
A type of solar cell made from multiple silicon crystals, offering lower cost but also lower efficiency.
Microgeneration
Small-scale electricity generation — typically rooftop solar panels — by homes or small businesses.
MPPT (Maximum Power Point Tracking)
An algorithm used by inverters to extract the maximum possible power from solar panels at all times.
Solar Resource Map
A map showing solar energy potential across different regions, used to estimate panel output by location.
PVGIS
A free EU tool that estimates solar panel output for any location using satellite-based solar radiation data.
AC/DC (Alternating/Direct Current)
Two types of electrical current — solar panels produce DC, which inverters convert to AC for home use.
EV Charging (Solar)
Using solar-generated electricity to charge an electric vehicle, significantly reducing running costs.
Heat Pump
A device that extracts heat from the air or ground to heat your home, often paired with solar panels for maximum savings.
Solar Farm
A large-scale ground-mounted solar installation that generates electricity for the grid, typically 1MW or larger.
Embedded Generation
Electricity generation connected directly to the distribution network rather than the transmission network.
Solar String
A series of solar panels wired together in sequence and connected to a single inverter input.
Bifacial Solar Panel
A solar panel that generates electricity from sunlight hitting both its front and back sides.
PV System
A complete solar setup including panels, inverter, wiring, mounting, and optional battery storage.
Equipment
Solar Panel
A device made of connected photovoltaic cells that converts sunlight into electricity for homes and businesses.
Inverter
A device that converts the DC electricity produced by solar panels into AC electricity used in your home.
String Inverter
A central inverter that handles all solar panels connected in series (a 'string').
Microinverter
A small inverter attached to each individual solar panel, converting DC to AC at the panel level.
Hybrid Inverter
An inverter that manages both solar panels and battery storage in a single unit.
Battery Storage
A rechargeable battery system that stores surplus solar electricity for use when the sun is not shining.
Flat Plate Collector
A type of solar thermal panel with a flat, dark absorber plate that heats fluid as sunlight passes through a glass cover.
Evacuated Tube Collector
A solar thermal collector using vacuum-sealed glass tubes to absorb heat more efficiently than flat plates.
Smart Meter
A digital electricity meter that records import and export data, enabling solar export payments and time-of-use tariffs.
Power Optimiser
A device attached to each solar panel that maximises its individual output, improving performance in partial shading.
Solar Monitoring
Software and apps that track your solar system's performance, showing real-time and historical generation data.
Solar Panel Warranty
Guarantees covering defects (product warranty, 12–25 years) and minimum output levels (performance warranty, 25–30 years).
Solar Diverter
A device that automatically redirects surplus solar electricity to heat your water tank instead of exporting to the grid.
Solar Array
A group of solar panels connected together in a system, mounted on a roof or ground frame.
Export Meter
A meter that measures the electricity your solar system sends back to the grid.
Generation Meter
A meter that tracks the total amount of electricity your solar PV system produces.
Financial & Incentives
Feed-in Tariff
A payment made to homeowners for excess solar electricity exported to the national grid.
Export Payment
Money paid by your electricity supplier for each kWh of surplus solar electricity you send to the grid.
SEAI Grant
A government grant from the Sustainable Energy Authority of Ireland to help homeowners pay for solar panels.
SEAI
The Sustainable Energy Authority of Ireland — the government body that administers energy grants and standards.
Payback Period
The time it takes for energy savings from solar panels to equal the initial cost of the system.
ROI (Return on Investment)
The total financial return from solar panels over their lifetime, expressed as a percentage of the initial cost.
Net Metering
A billing arrangement where your electricity meter runs backwards when you export solar power, offsetting your bill.
Zero VAT on Solar
The 0% VAT rate applied to residential solar panel installations in Ireland since May 2023.
Energy Independence
Reducing reliance on grid electricity by generating your own power from solar panels and storing it in batteries.
Solar Lease / PPA
Financing options where a company installs solar panels on your roof and you pay a monthly fee or reduced electricity rate.
Clean Export Guarantee (CEG)
An Irish scheme where electricity suppliers pay homeowners for excess solar electricity exported to the grid.
Time-of-Use Tariff
An electricity pricing plan where the rate per kWh varies depending on the time of day.
Measurement & Performance
kWp (Kilowatt Peak)
The maximum power output a solar panel or system can produce under standard test conditions.
kWh (Kilowatt-hour)
A unit of energy equal to using 1,000 watts for one hour — the standard unit on Irish electricity bills.
Self-Consumption
The percentage of solar electricity you use directly in your home rather than exporting to the grid.
BER Rating
Building Energy Rating — Ireland's energy efficiency label for homes, rated A1 (best) to G (worst).
NZEB (Nearly Zero Energy Building)
A building standard requiring very high energy efficiency and significant on-site renewable energy generation.
Solar Irradiance
The amount of solar energy falling on a surface, measured in watts per square metre (W/m²) or kWh/m² per year.
Solar Panel Efficiency
The percentage of sunlight energy that a solar panel converts into electricity — typically 20–24% for modern panels.
Panel Degradation
The gradual reduction in solar panel output over time, typically 0.3–0.5% per year.
Standard Test Conditions (STC)
The laboratory conditions (1,000 W/m², 25°C) used to rate solar panel output — real-world output varies.
Temperature Coefficient
A measure of how much a solar panel's output decreases as temperature rises above 25°C.
Carbon Footprint
The total greenhouse gas emissions associated with an activity, product, or system over its lifetime.
Peak Sun Hours
The number of hours per day when solar irradiance averages 1,000 W/m² — used to estimate daily panel output.
Kilowatt (kW)
A unit of power equal to 1,000 watts — used to measure the instantaneous output of solar panels.
Import (Electricity)
Electricity drawn from the national grid when your solar panels are not producing enough to meet demand.
Voltage
The electrical pressure that pushes electric current through a circuit — measured in volts (V).
Installation & Setup
Grid Connection
The link between your solar panel system and the national electricity grid, allowing import and export of power.
Anti-Islanding
A safety feature that automatically shuts down your solar system during a grid power outage to protect line workers.
Roof Orientation
The compass direction your roof faces, which affects how much solar energy your panels can capture.
Roof Pitch
The angle of your roof slope, which affects solar panel output — the ideal pitch in Ireland is 30–35 degrees.
Mounting System
The racking and brackets that secure solar panels to your roof, designed to withstand wind, rain, and snow.
Planning Permission
Formal approval from your local authority to make changes to your property — not usually needed for residential solar.
Grid-Tied System
A solar system connected to the electricity grid, allowing import of power when needed and export of surplus.
Off-Grid System
A standalone solar system with battery storage that operates independently of the electricity grid.
Commercial Solar
Solar panel systems installed on business premises — offices, warehouses, farms — typically 10–200 kWp.
MCS Certification
Microgeneration Certification Scheme — a UK quality standard for renewable energy installations and installers.
Shade Analysis
An assessment of how shadows from trees, chimneys, and nearby buildings affect solar panel performance on your roof.
ESB Networks
The company that operates Ireland's electricity distribution grid and manages microgeneration connections.
Fixed Tilt System
Solar panels mounted at a fixed angle, optimised for year-round energy production.
All Solar Terms A–Z
A
- AC/DC (Alternating/Direct Current)
- Two types of electrical current — solar panels produce DC, which inverters convert to AC for home use.
- Anti-Islanding
- A safety feature that automatically shuts down your solar system during a grid power outage to protect line workers.
B
- Battery Storage
- A rechargeable battery system that stores surplus solar electricity for use when the sun is not shining.
- BER Rating
- Building Energy Rating — Ireland's energy efficiency label for homes, rated A1 (best) to G (worst).
- Bifacial Solar Panel
- A solar panel that generates electricity from sunlight hitting both its front and back sides.
C
- Carbon Footprint
- The total greenhouse gas emissions associated with an activity, product, or system over its lifetime.
- Clean Export Guarantee (CEG)
- An Irish scheme where electricity suppliers pay homeowners for excess solar electricity exported to the grid.
- Commercial Solar
- Solar panel systems installed on business premises — offices, warehouses, farms — typically 10–200 kWp.
E
- Embedded Generation
- Electricity generation connected directly to the distribution network rather than the transmission network.
- Energy Independence
- Reducing reliance on grid electricity by generating your own power from solar panels and storing it in batteries.
- ESB Networks
- The company that operates Ireland's electricity distribution grid and manages microgeneration connections.
- EV Charging (Solar)
- Using solar-generated electricity to charge an electric vehicle, significantly reducing running costs.
- Evacuated Tube Collector
- A solar thermal collector using vacuum-sealed glass tubes to absorb heat more efficiently than flat plates.
- Export Meter
- A meter that measures the electricity your solar system sends back to the grid.
- Export Payment
- Money paid by your electricity supplier for each kWh of surplus solar electricity you send to the grid.
F
- Feed-in Tariff
- A payment made to homeowners for excess solar electricity exported to the national grid.
- Fixed Tilt System
- Solar panels mounted at a fixed angle, optimised for year-round energy production.
- Flat Plate Collector
- A type of solar thermal panel with a flat, dark absorber plate that heats fluid as sunlight passes through a glass cover.
G
- Generation Meter
- A meter that tracks the total amount of electricity your solar PV system produces.
- Grid Connection
- The link between your solar panel system and the national electricity grid, allowing import and export of power.
- Grid-Tied System
- A solar system connected to the electricity grid, allowing import of power when needed and export of surplus.
H
- Heat Pump
- A device that extracts heat from the air or ground to heat your home, often paired with solar panels for maximum savings.
- Hybrid Inverter
- An inverter that manages both solar panels and battery storage in a single unit.
I
- Import (Electricity)
- Electricity drawn from the national grid when your solar panels are not producing enough to meet demand.
- Inverter
- A device that converts the DC electricity produced by solar panels into AC electricity used in your home.
K
- Kilowatt (kW)
- A unit of power equal to 1,000 watts — used to measure the instantaneous output of solar panels.
- kWh (Kilowatt-hour)
- A unit of energy equal to using 1,000 watts for one hour — the standard unit on Irish electricity bills.
- kWp (Kilowatt Peak)
- The maximum power output a solar panel or system can produce under standard test conditions.
M
- MCS Certification
- Microgeneration Certification Scheme — a UK quality standard for renewable energy installations and installers.
- Microgeneration
- Small-scale electricity generation — typically rooftop solar panels — by homes or small businesses.
- Microinverter
- A small inverter attached to each individual solar panel, converting DC to AC at the panel level.
- Monocrystalline
- The most efficient type of silicon solar cell, made from a single continuous crystal structure.
- Mounting System
- The racking and brackets that secure solar panels to your roof, designed to withstand wind, rain, and snow.
- MPPT (Maximum Power Point Tracking)
- An algorithm used by inverters to extract the maximum possible power from solar panels at all times.
N
- Net Metering
- A billing arrangement where your electricity meter runs backwards when you export solar power, offsetting your bill.
- NZEB (Nearly Zero Energy Building)
- A building standard requiring very high energy efficiency and significant on-site renewable energy generation.
O
- Off-Grid System
- A standalone solar system with battery storage that operates independently of the electricity grid.
P
- Panel Degradation
- The gradual reduction in solar panel output over time, typically 0.3–0.5% per year.
- Payback Period
- The time it takes for energy savings from solar panels to equal the initial cost of the system.
- Peak Sun Hours
- The number of hours per day when solar irradiance averages 1,000 W/m² — used to estimate daily panel output.
- Photovoltaic Cell
- The smallest unit of a solar panel that converts sunlight into electricity through the photovoltaic effect.
- Planning Permission
- Formal approval from your local authority to make changes to your property — not usually needed for residential solar.
- Polycrystalline
- A type of solar cell made from multiple silicon crystals, offering lower cost but also lower efficiency.
- Power Optimiser
- A device attached to each solar panel that maximises its individual output, improving performance in partial shading.
- PV System
- A complete solar setup including panels, inverter, wiring, mounting, and optional battery storage.
- PVGIS
- A free EU tool that estimates solar panel output for any location using satellite-based solar radiation data.
R
- ROI (Return on Investment)
- The total financial return from solar panels over their lifetime, expressed as a percentage of the initial cost.
- Roof Orientation
- The compass direction your roof faces, which affects how much solar energy your panels can capture.
- Roof Pitch
- The angle of your roof slope, which affects solar panel output — the ideal pitch in Ireland is 30–35 degrees.
S
- SEAI
- The Sustainable Energy Authority of Ireland — the government body that administers energy grants and standards.
- SEAI Grant
- A government grant from the Sustainable Energy Authority of Ireland to help homeowners pay for solar panels.
- Self-Consumption
- The percentage of solar electricity you use directly in your home rather than exporting to the grid.
- Shade Analysis
- An assessment of how shadows from trees, chimneys, and nearby buildings affect solar panel performance on your roof.
- Smart Meter
- A digital electricity meter that records import and export data, enabling solar export payments and time-of-use tariffs.
- Solar Array
- A group of solar panels connected together in a system, mounted on a roof or ground frame.
- Solar Diverter
- A device that automatically redirects surplus solar electricity to heat your water tank instead of exporting to the grid.
- Solar Farm
- A large-scale ground-mounted solar installation that generates electricity for the grid, typically 1MW or larger.
- Solar Irradiance
- The amount of solar energy falling on a surface, measured in watts per square metre (W/m²) or kWh/m² per year.
- Solar Lease / PPA
- Financing options where a company installs solar panels on your roof and you pay a monthly fee or reduced electricity rate.
- Solar Monitoring
- Software and apps that track your solar system's performance, showing real-time and historical generation data.
- Solar Panel
- A device made of connected photovoltaic cells that converts sunlight into electricity for homes and businesses.
- Solar Panel Efficiency
- The percentage of sunlight energy that a solar panel converts into electricity — typically 20–24% for modern panels.
- Solar Panel Warranty
- Guarantees covering defects (product warranty, 12–25 years) and minimum output levels (performance warranty, 25–30 years).
- Solar PV
- Solar photovoltaic (PV) technology converts sunlight directly into electricity using semiconductor cells.
- Solar Resource Map
- A map showing solar energy potential across different regions, used to estimate panel output by location.
- Solar String
- A series of solar panels wired together in sequence and connected to a single inverter input.
- Solar Thermal
- A system that uses sunlight to heat water directly, as opposed to generating electricity.
- Standard Test Conditions (STC)
- The laboratory conditions (1,000 W/m², 25°C) used to rate solar panel output — real-world output varies.
- String Inverter
- A central inverter that handles all solar panels connected in series (a 'string').
T
- Temperature Coefficient
- A measure of how much a solar panel's output decreases as temperature rises above 25°C.
- Time-of-Use Tariff
- An electricity pricing plan where the rate per kWh varies depending on the time of day.
V
- Voltage
- The electrical pressure that pushes electric current through a circuit — measured in volts (V).
Z
- Zero VAT on Solar
- The 0% VAT rate applied to residential solar panel installations in Ireland since May 2023.
Related Guides
John Rooney is the founder of Solar Info and has been covering the Irish solar energy market since 2023. He fact-checks all content against official SEAI data and maintains relationships with SEAI-registered installers across Ireland.