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Solar glossary

The words you will meet in solar quotes, guides and rules, explained simply.

AC (alternating current): The kind of electricity your home's sockets and appliances use.
AC-coupled battery: A battery with its own inverter, connected to your home's normal wiring. The usual way to add a battery to existing panels.
Array: All the solar panels in a system, together.
Article 4 direction: A council decision that removes permitted development rights in an area, so you need to apply for planning permission.
Building warrant: In Scotland, approval for certain building work under the building standards.
Clipping: When an inverter limits its output, so some of what the panels could produce is lost.
Commissioning: Testing a system, switching it on and recording the results.
Consumer unit: Your fuse box, where the circuits in your home start.
DC (direct current): The kind of electricity solar panels and batteries produce and store.
DC-coupled battery: A battery that shares a hybrid inverter with the solar panels.
DC to AC ratio: The panels' total rating divided by the inverter's rating.
Depth of discharge: How much of a battery's capacity can be used before it stops discharging.
DNO (distribution network operator): The company that runs the local power cables in your area. It is not your energy supplier.
ENA register: The Energy Networks Association's list of compliant plug-in solar devices and type-tested equipment.
Export: Electricity you send to the grid.
Export limitation: A setting or device that caps how much a system can send to the grid.
G98: The Great Britain process for connecting small type-tested generation (up to 16 amps per phase): connect, then notify within 28 days.
G98/NI: Northern Ireland's version of G98, for NIE Networks.
G99: The process for larger generation and storage: apply to the network operator before installing.
HIES: Home Insulation and Energy Systems: one of the two consumer codes MCS installers can belong to.
Hybrid inverter: An inverter that handles both solar panels and a battery.
Import: Electricity you buy from the grid.
Inverter: The box that turns DC from panels or a battery into AC for your home.
kW (kilowatt): Power: how fast electricity is made or used.
kWh (kilowatt hour): Energy: how much electricity is made or used. One 'unit' on your bill.
kWp (kilowatt peak): A solar system's rated output under standard test conditions.
Listed building consent: Separate consent needed for work affecting a listed building.
MCS: The Microgeneration Certification Scheme, which certifies installers and products. Usually needed for export payments.
Microinverter: A small inverter fitted to each panel, or the inverter in a plug-in kit.
MPPT: Maximum power point tracking: how an inverter gets the most from each string of panels.
Network operator: See DNO.
Part P: The part of the Building Regulations in England and in Wales that covers electrical work in homes.
Permitted development: Building work you can do without applying for planning permission, if you meet the conditions.
Plug-in solar: A small solar kit with a three-pin plug that connects to a wall socket, limited to 800 W. Also called balcony solar.
Power optimiser: A small box fitted to each panel that improves output while still feeding a central inverter.
Prior approval: A lighter application to the council, needed in some protected areas.
RCD: Residual current device: a safety switch that cuts the power when it detects a fault.
RECC: The Renewable Energy Consumer Code: one of the two consumer codes MCS installers can belong to.
Round-trip efficiency: The share of the energy put into a battery that you get back out.
SEG (Smart Export Guarantee): The Great Britain scheme requiring suppliers to offer payment for exported electricity.
Self-consumption: The share of your solar electricity you use as it is made.
Standing charge: A fixed daily charge on your bill, whatever you use.
String: A group of panels wired in series.
Time-of-use tariff: A tariff with different prices at different times of day, often cheaper overnight.
Type Test Register: The Energy Networks Association's list of equipment tested for connection under G98.
Usable capacity: The part of a battery's capacity you can actually use.
Wired-in system: A solar system connected by an electrician to its own circuit at the consumer unit, instead of plugged into a socket.

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Updated 2026-10-02.