The terms you will meet in a UK quote, in plain English.
A
AC (alternating current) The form of electricity your house uses and the grid supplies. Panels produce DC, so an inverter converts it.
AC coupled A battery with its own inverter, added alongside an existing solar system rather than integrated with it. See hybrid systems.
Anti-islanding The safety function that shuts a system down when the grid fails, so it cannot put power onto lines engineers may be working on. It is why solar does not work in a power cut unless backup is fitted.
Article 4 Direction A local authority order removing permitted development rights in a defined area. If one applies, you need planning permission for work that would otherwise be automatic.
B
Backup Equipment allowing a battery to power selected circuits during a power cut. Not included as standard. See power cuts.
Bifacial A panel that collects light on both faces. Needs reflected light from behind, so largely irrelevant on a pitched roof.
BS 7671 The UK wiring regulations. Amendment 4, published Apr 2026, introduced Chapter 57 covering battery installations, mandatory from 15 Oct 2026.
C
Clipping When panels briefly produce more than the inverter can convert and output is limited. Normal, and small over a UK year.
Consumer code A scheme setting standards for contracts, cancellation rights, deposit protection and complaints. RECC and HIES are the two in this market, both operating under TrustMark. Worth having; ask your installer whether they belong to one. See choosing an installer.
COP (coefficient of performance) Heat pump efficiency at a single test condition. Heat out divided by electricity in. Not the figure to judge running costs by. See SPF.
D
DC (direct current) What panels produce. Converted to AC by the inverter.
DC coupled Solar charges the battery as DC without conversion to AC first. Slightly more efficient and the normal arrangement for a new installation.
Degradation The slow annual decline in a panel’s output. See degradation.
DNO (distribution network operator) The company owning the wires in your street. Not your supplier and you do not choose it. It has to be told about your system. See grid connection.
E
EPC (energy performance certificate) The rating for a property’s energy efficiency. No longer a prerequisite for the Boiler Upgrade Scheme.
Export Electricity you send to the grid rather than using. Paid for under the Smart Export Guarantee, at roughly half the value of a unit used at home. See export share.
Export limiting Restricting how much a system can send to the grid, often to stay under the 3.68kW threshold. Your panels can be larger than your export limit.
F
Feed-in Tariff (FiT) The closed scheme that paid a government-set rate for generation and export. Closed to new applicants after 31 Mar 2019. Existing households keep their payments.
Future Homes Standard Comes into force in England on 24 Mar 2027. Requires solar and clean heating on the vast majority of new build homes.
G
G98 The connection route for generation up to 3.68kW per phase. The installer notifies the network operator within 28 days of commissioning. No prior permission needed.
G99 The route above 3.68kW per phase. Application to the network operator before installation, and they can limit it or require works.
H
Hybrid inverter An inverter handling both solar and a battery. Fit one if there is any chance you will add storage later.
I
Insurance-backed guarantee A workmanship warranty underwritten by an insurer, so it survives the installer ceasing to trade. Worth asking about specifically.
Inverter Converts DC from the panels to AC for the house. The component most likely to need replacing. See choosing an inverter.
K
kW (kilowatt) A measure of power, or rate. A system’s size is given in kW or kWp.
kWh (kilowatt hour) A measure of energy, or quantity. What your bill charges for, and what generation estimates are given in. A 1kW appliance running for an hour uses 1kWh.
kWp (kilowatt peak) A panel array’s rated output under standard test conditions. The usual way to state system size.
M
MCS (Microgeneration Certification Scheme) Certifies products and installers. Without it you cannot claim the Smart Export Guarantee or a Boiler Upgrade Scheme grant. The single most important thing to check about an installer.
Microinverter A small inverter on each panel. Each panel operates independently. See microinverters.
MPPT (maximum power point tracker) The part of an inverter that extracts the most it can from a string. Multiple MPPT inputs let panels on different roof faces be managed separately.
O
Optimiser A device on each panel, used with a string inverter, so one shaded panel does not hold back the others.
P
PAS 63100 The standard covering protection against fire for battery storage in dwellings.
Performance warranty A manufacturer’s guarantee of a minimum panel output after a given number of years. Separate from the product warranty. See warranties.
Permitted development Work allowed without a planning application, subject to conditions. Most roof-mounted solar on a house qualifies. See can I install panels.
Plug-in solar Small units up to 800W that plug into a domestic socket. Legal in Great Britain since 27 Aug 2026. See plug-in solar.
PV (photovoltaic) Generating electricity from light. As distinct from solar thermal, which heats water.
S
SCOP (seasonal coefficient of performance) A heat pump’s efficiency across a year, measured in a laboratory. Real installed performance is usually lower. See SPF.
SEG (Smart Export Guarantee) The scheme requiring larger suppliers to offer an export tariff. Suppliers set their own rates. See export payments.
Self-consumption The share of your generation you use at home rather than export. The single most important number in a solar quote, because a unit used is worth about twice a unit exported.
SPF (seasonal performance factor) A heat pump’s efficiency as actually installed, across a year. The figure to judge running costs by. The UK field trial median is 2.8. See heat pump running costs.
Solar diverter Sends surplus solar that would otherwise be exported into an immersion heater, turning a half-value export into a full-value saving.
Solar thermal Roof collectors that heat water directly. A different technology from PV. See solar hot water.
Standing charge A fixed daily amount on your energy bill regardless of usage. A household that removes its gas connection stops paying the gas one.
String Panels wired in series into an inverter. The string is limited by its weakest panel, which is why shading matters.
T
Time-of-use tariff Different electricity prices at different times of day. What makes a battery worth having. See smart tariffs.
TOPCon A current mainstream solar cell technology. See panel technologies.
U
TrustMark A government-endorsed quality scheme covering technical competence, customer service and trading practices. RECC and HIES both operate under it.
Usable capacity How much of a battery’s stated capacity you can actually use. Lower than the headline figure, and the one that matters.
V
VAT Currently 0% on installed solar, batteries and heat pumps in residential property until 31 Mar 2027, then 5%. Not 20%.