SolarEdge UK | All you need to know to go solar | Glossary
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Our solar energy glossary offers a collection of key terms and phrases, explained simply and concisely. 


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Alternating Current (AC) 

A type of electrical current that circuits and appliances in most homes utilise.
Expressed as a sine wave, the AC current periodically reverses direction and changes its magnitude continuously with time, which is in contrast to direct current (DC.)
Alternating Current (AC)


The direction that a roof or array faces (in the context of solar). The azimuth is measured in degrees, representing the angle between the roof and true north.



A mode of operation for the solar inverter that uses a battery or batteries to provide backup energy in the event of grid failure.


In the context of energy storage, a battery is a device that is used to store electrical energy using reversible chemical reactions. A battery is charged by passing a current through it in one direction and is discharged by changing chemical energy back into electrical energy in the opposite direction.

Batteries store energy in DC form, and have a positive and a negative terminal. In a solar PV system, inverters then convert the DC current to AC for general use. When selecting a battery for a PV system, a number of factors should be considered: (a) battery capacity should meet the household’s demand and the PV system’s production rate so that energy is not lost (b) the battery’s charging and discharging rate should be fast enough to meet energy needs (c) the battery should be warranted for outdoor and indoor installation.


Battery Capacity

The total amount of electrical energy a battery can store. Because many batteries can be damaged if they are completely discharged, a battery’s capacity is usually higher than its usable capacity. Battery capacity is measured in kilowatt hours (kWh), which shows how much total energy the battery can provide.

Both the total energy, and useable energy will be shown in kWh on the specification, or data sheets.


Battery Coupling

This refers to the way in which solar inverters are coupled with a battery. AC coupling converts solar energy to AC before converting it back to DC for battery storage. This results in lost energy. With DC coupling, the inverter directs energy directly from solar panels to the batteries without converting it. DC coupling has advantages that include fewer power conversions, higher efficiency and the ability to support PV oversizing. AC coupling can also add development time and cost to a project.


Bypass Diode

A bypass diode, located in the junction box, allows underperforming solar panels to be bypassed in order to prevent them from dragging down the production of the other panels in the same string. This is a standard component in PV panels.


BOS (Balance of System)

Components and equipment in a PV system excluding the modules (inverters, Power Optimizers, wiring, conduit, combiner box).



Tests and procedures required to bring a newly installed PV plant into operation. Commissioning is carried out to show that all systems and components of the PV plant are designed and installed correctly, that the plant is fit for purpose and that it meets the operational requirements of the system owner.

Community Solar

A solar power system which generates electricity that is used by more than one household. Sometimes called a solar garden, it allows members of a community who cannot (or do not wish to) install solar on their property to enjoy the benefits of solar.


When the DC solar system output exceeds the maximum capacity of the inverter and power is lost.


Direct Current (DC)


DC current is the flow of electric charge in one direction. This type of electricity is produced by batteries and solarpanels, also known as panels when the sun’s rays hit them. The inverter converts DC into Alternating Current (AC) electricity to be used around the home.

Solargraph DC



DC/AC Ratio

The ratio of installed solar DC capacity to the Alternating Current (AC) power rating of the inverter. E.g. A 6kW DC solar array paired with a 5kW rated inverter would have a DC/AC ratio of 1.2.


Energy Storage

The capture of energy produced at one time for use at a later time. Households can use batteries to store solar energy generated by solar energy systems during the day for use during the evening. By storing energy in batteries, users can increase their energy independence, self-consumption and the ROI of their solar energy system.


Stands for Engineering, Procurement and Construction. These are companies that assist in facilitating large commercial solar contracts. They serve as the middleman between the client and solar component manufacturers and builders to negotiate contracts.

European Weighted Efficiency

An industry-wide measure of solar PV equipment efficiency based an averaged operating efficiency over a yearly power distribution corresponding to a middle-Europe climate.
This was proposed by the Joint Research Center (JRC/Ispra), based on the Ispra climate (Italy). It is measured as the ratio of DC input power to the AC output power and is expressed as a percentage.



The utility infrastructure that is responsible for the transmission and distribution of electricity to consumers.


Grid-tied Solar Systems

A solar PV system that is connected to the electrical power grid. The majority of residential solar is grid tied. When we use more energy than is produced by the solar PV system, energy from the utility grid will keep the lights on at home.

Ground Mount Systems

Rather than installing solar panels on a roof, a ground mount solar system is a system where solar panels are attached to a racking system with its foundation directly in the ground.

GSM Card

The component inside the SolarEdge inverters that links the inverter to the network and the SolarEdge Monitoring Portal through cellular communication.




The family of SolarEdge inverters that is 25% smaller than the standard inverter and has 99% efficiency and an oversizing of 155%. SetApp enabled HD-Wave inverters do not have an LCD screen, and instead are remotely accessed using SetApp.


HD-Wave Technology

The software associated with the SolarEdge HD-Wave family of products.


I-V curve

A graphical plot of the current (I) versus the voltage (V) from a photovoltaic device as the load is increased from a short circuit (no load) condition to an open circuit (maximum load) condition. The shape of the curve characterises cell performance.


Junction Box

The output interface installed on the back of each solar panel. Each junction box includes a bypass diode that wires the PV panel connectors together and keeps the current flow in one direction.



A unit of energy or power measured over a period of time. We are charged by the utility company as an amount per kWh. E.g. the amount of power that ten 100W lightbulbs use in one hour is 1kWh.


A kW is a unit of power. 1kW is equivalent to 1000W of power. Solar PV systems are measured in kW.


Levelised Cost Of Energy (LCOE)

A way of calculating the cost of generating a unit of electricity from a specific energy production system. It is calculated by dividing the overall cost of the system (including operation and maintenance costs) by the number of energy units the system is expected to produce during its lifetime. In many locations, the LCOE of solar energy is lower than that of energy from the grid – this means that solar has reached grid parity.



Module Level Power Electronics. Microinverter and Power Optimizer technologies are often referred to as MLPEs.


Maximum Power Point Tracking is a used to maximise power extraction from PV systems. Since each solar panel performs at a different level, due to a variety of factors, MPPT is an algorithm that finds the maximum power point of each panel. For example, if panels are soiled, covered in snow, leaves, or bird droppings, shaded, have a different manufacturing tolerance, or age at different rates, their energy production will vary. Some inverters perform MPPT at the string level, while other inverters perform MPPT at the panel level. String-level MPPT leads to panel-level mismatch which causes energy losses. However, when MPPT takes place at the panel-level, the energy loss from panel-level mismatch is eliminated.


The Energy Meter is a device that is used to measure and monitor production, consumption and import/export of energy to and from the grid.


NEC 2014/NEC 2017

The National Electrical Code is a standard that governs safe installation of electrical wiring and equipment in the United States.

It includes the latest rapid shutdown requirement stating that conductors around the solar array must be de-energized to 30V or less within 30 seconds of initiating rapid shutdown, and that the system must be shut down within 1’ of the solar array in all directions.

Note: This is not a recognised regulation in the UK. At present it is the only standard globally.


Net Metering

The process of obtaining credits from the utility company for solar system production in some countries. Solar PV systems in regions with net metering include a meter that measures the amount of electricity that comes into the home as well as the amount that the solar PV system sends back to the grid. This allows the homeowner to generate credit with the utility company when the solar PV system produces more energy than the house is consuming and that excess electricity is sent to the grid.


Older SolarEdge inverters that had to be programmed via an LCD screen on the inverter.



A type of solar PV system that runs independently from the utility grid. Off-grid systems feature enough solar panels and battery storage to generate sufficient energy onsite, without access to utility-generated electricity.

Operations and maintenance (O&M)

The ongoing operational processes of a solar energy system, including cleaning, repairs, replacement of parts, bill management and so on. It primarily refers to larger-scale commercial and utility-scale solar PV systems.


A way to increase the output of a solar energy system. Oversizing a solar energy system means that solar production has a higher peak capacity than the inverter rating. Simply put, oversizing is a cost-effective way to maximise a solar energy system’s production by increasing the total capacity of the solar panels so that it is higher than the capacity of the inverter. While energy will be lost at peak production, more energy will be harvested throughout the day. Oversizing can be a good way to increase solar energy production in areas where inverter size is restricted.


Panel Mismatch

Panel mismatch occurs when lower performing panels pull down the performance of neighbouring panels in the same string. The causes of panel mismatch vary and include manufacturing tolerance, panels aging at different rates, shading, soiling, bird droppings, snow and fallen leaves blocking the sunlight. Panel mismatch reduces the output of solar energy systems, which decreases system ROI.

Peak Demand

The maximum energy demand or load in a specified time period.

Photovoltaic (PV) Panel

A PV panel, also referred to as a solar panel, comprises photovoltaic solar cells connected in series. PV panels are installed on the rooftop where they absorb photons (light energy) and generate electricity. PV panels are connected in a string to form a complete solar-power-generating unit called a PV array.

Power purchase agreement (PPA)

A contract with a solar company to have a solar energy system installed on a roof. With a solar PPA, the site owner agrees to pay the company a per kilowatt-hour rate for the electricity produced by the solar panels.

PV Array

A Photovoltaic solar system. A linked collection of solar panels on a roof is called an ‘array’.

Power Density

The power density of a solar PV module or panel is calculated in watts per square metre (W/m2).

Power Optimizer

Connected by installers to each solar module, also known as panel, Power Optimizers are DC-to-DC converters designed to maximise the energy harvested from PV systems by individually tracking the maximum power point of each individual panel. Advanced Power Optimizers turn every solar panel into a smart panel. Power Optimizers are also responsible for monitoring each individual panel’s performance.

PV Inverter

PV inverters were originally developed to convert direct current (DC) generated by PV panels to alternating current (AC) for use in the home or to feed into the grid. One of the most common types of inverters is a string inverter, which performs both conversion and MPPT at the string level.

Standard string inverters offer limited monitoring possibilities, create energy losses, limit design flexibility, and in some regions require the installation of additional safety hardware. Other types of inverters available are DC-optimised inverters and micro-inverters.

In recent years the role of the PV inverter has expanded into smart energy management, including storage, grid interaction, home energy, EV charging, monitoring, safety and more.


PV Monitoring

A solar energy monitoring system offers information about the performance of the PV system, such as how much energy is produced, consumed and fed into the grid. Without high-resolution monitoring, it can be challenging to understand the PV system’s performance. Monitoring increases a system owner’s insight into their PV system’s performance and helps them understand if something needs to be repaired. Furthermore, monitoring often allows installers to perform remote troubleshooting, which means quicker problem-solving and higher system uptime. There are different types of PV monitoring – embedded monitoring systems, add-ons, monitoring at the string-level, and monitoring at the panel-level. Panel-level monitoring provides the highest resolution insight.




The mounting system used to affix solar panels to the roof, building surface or ground.



(Return Merchandise Authorisation) Customer request for a replacement product within warranty parameters.


SafeDC™ Technology

A unique, SolarEdge feature designed to automatically reduce PV panels DC voltage to a safe level whenever the inverter or grid power is shut down. De-energizing the PV panels to touch-safe levels ensures maximum safety for installers, maintenance workers and firefighters.


When a household or business uses electricity generated by its own solar energy system, it is called self-consumption. Self-consumption can increase a PV system’s ROI, unless the system is in a net metering or FiT (feed-in tariff) market.


The installer app used to activate and configure inverters, which is carried out through a smartphone.

Single Phase Power

Distribution of alternating current (AC) in which all voltages vary in unison. Single phase power is the most common household power circuit in the UK.

Solar Lease

A contract with a solar company to have a solar energy system installed on a roof. With a solar lease, the owner agrees to pay a fixed monthly fee to rent the system in exchange for the benefits (i.e. the electricity) the system provides.

Step Down Transformer

An electrical device that reduces the voltage at its input (the primary winding) to a lower level at its output (the secondary winding). Transformers are used to connect electrical systems with different voltage levels.

String Inverter

An inverter that connects to a string of solar panels. String inverters are among the more common types of inverters used in residential solar energy systems today. Standard string inverters perform both DC/AC conversion and MPPT at the inverter level. This means energy losses, limited monitoring capability and lack of design flexibility. Depending on local safety standards, string inverters may also require the installation of additional safety equipment.


A number of photovoltaic modules or panels interconnected electrically in series to produce the operating voltage required by the load. This term also applies when using Power Optimizers.



The technology associated with our commercial inverter products i.e. Three Phase Inverter with Synergy Technology.


Three Phase Power 

Distribution of alternating current (AC) which essentially uses three separate, alternating supplies. The three supplies are of the same magnitude, and vary at the same frequency but are out of phase with each other by 1/3 of the time in a full cycle (or 120°). Three phase power is usually used by electrical grids to transfer electricity, or to power industrial machinery, large motors and other heavy loads. A three-phase system has four cables: three current carrying conductors and one neutral. Most residential systems in the UK utilise single-phase power.



Time of Use. A utility rate structure that charges consumers more at the highest demand times of day to encourage the use of energy at off peak times.


Watts (W)

A measure of power. Appliances, lightbulbs, as well as solar panels are measured in Watts. 1kW = 1,000 Watts.


Witness Testing

Carried out by the distribution network operator (DNO) on site to witness the commissioning engineer, testing the grid protection systems associated with a PV system. It is carried out to ensure that the equipment generating electrical power which is to be connected to the grid operates correctly and is safe. This may also include the witness testing of the G100 export limitation scheme.