Solar glossary
The jargon you’ll meet in quotes and guides, in plain English.
- ADR (alternative dispute resolution)
- An independent way to settle a dispute without going to court.
- Degradation
- The slow loss of a panel’s output as it ages — a median of about 0.5% a year in field studies.
- DNO (distribution network operator)
- The company that runs the local electricity network. It isn’t your energy supplier.
- Export
- Spare solar electricity that flows out to the grid.
- Export limitation
- A setting that caps how much a system can export to the grid.
- Export MPAN
- The meter point number your network operator sets up so a supplier can pay you for exports.
- Feed-in Tariff (FiT)
- The earlier scheme that paid for solar generation and export. It closed to new applicants in 2019.
- G98 and G99
- The Energy Networks Association’s rules for connecting generators. G98 covers small type-tested systems up to 16 A per phase (about 3.68 kW on a single-phase home) — “connect and notify”. G99 covers larger systems, which need approval first.
- Hybrid inverter
- An inverter that manages both solar panels and a battery.
- Inverter
- The box that turns the panels’ direct current (DC) into the alternating current (AC) your home uses. Types include string inverters, hybrid inverters and microinverters.
- Kk (kWh per kWp)
- The MCS figure for how many kWh each kWp makes in a year, for a given postcode zone, roof pitch and direction.
- kW (kilowatt)
- A rate of power — how fast electricity is being made or used at a given moment.
- kWh (kilowatt-hour)
- A unit of energy: the “unit” on your electricity bill. Export payments are also paid per kWh.
- kWp (kilowatt peak)
- A solar array’s rated output under standard test conditions — the panels’ wattages added together. Real output is usually lower and changes with the weather and the time of day.
- Listed building consent
- Separate permission needed for works that affect a listed building.
- MCS
- The Microgeneration Certification Scheme, the UK certification scheme for small-scale renewable installers and products. See our guide.
- MCS certificate
- Proof that a system was installed by an MCS-certified installer. You need it (or an equivalent) for the Smart Export Guarantee and for a Warm Homes Loan, and many insurers require MCS.
- MCS postcode zone
- One of the climate zones MCS uses to look up Kk — the same zones as the government’s SAP energy-rating method.
- Microinverter
- A small inverter fitted to one or two panels. Plug-in solar kits use one.
- Orientation
- The direction panels face, measured in degrees from due south.
- Payback period
- How many years it takes for savings and export income to add up to what the system cost.
- Permitted development
- Building work you can do without applying for planning permission, within set limits. See planning permission.
- Pitch
- The panels’ angle from horizontal: 0° is flat, 90° is vertical.
- Plug-in solar
- A small kit of up to 800 W that plugs into a wall socket. Legal in Great Britain since 27 August 2026. See our guide.
- PV-T (hybrid) panels
- Panels that make both electricity and heat.
- RECC and HIES
- Consumer codes approved by the Chartered Trading Standards Institute for renewables installers. Membership is voluntary under MCS’s 2025 scheme.
- Self-consumption
- The share of your solar electricity that you use in your home, rather than export.
- Self-sufficiency
- The share of your home’s electricity that comes from your own solar (and battery).
- Shade factor
- A number between 0 and 1 that reduces a generation estimate to allow for shading. 1 means no shading.
- Smart Export Guarantee (SEG)
- The rule in Great Britain that larger electricity suppliers must offer a tariff paying for electricity small generators export. See our guide.
- Smart meter
- A meter that can record your import and export every half-hour.
- Solar PV (photovoltaic)
- Panels that turn daylight directly into electricity.
- Solar thermal
- Panels that heat water rather than making electricity.
- Time-of-use tariff
- An electricity tariff with cheaper and dearer times of day.
- TrustMark
- The government-endorsed quality scheme for trades working in and around the home.
- Usable battery capacity
- The amount of a battery’s stored energy you can actually use, usually less than its nominal size.
Missing a term? Tell us.