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Solar glossary: the words on a roof and a quote
Quotes and surveys use roofers' and electricians' words. These are the ones you are most likely to meet, with what each means for a Southport house.
Figures checked at source on 3 November 2026. Written by SEO Dons, who neither sell nor fit solar panels.
- Array
- The panels on one roof, or one face of it, taken together.
- Article 4 direction
- A council order that removes some permitted development rights in a named area, so work that would normally need no application does need one there.
- Batten
- The horizontal timber strips nailed across the rafters that slates or tiles hang on. Panel brackets go through to the rafters, not just the battens.
- Bracket (roof hook)
- The metal fixing screwed to a rafter that the rails sit on. Slate roofs use brackets or plates made to sit flat under the slates.
- Clamp
- The clip that holds a panel to its rail. The roof planner allows 20 mm between panels for clamps.
- Consumer unit
- The box of switches and fuses where the house wiring starts. The solar system connects here through its own protected circuit.
- Eaves
- The lower edge of a roof slope, where the gutter runs. The planner's first measurement is the length along it.
- Flashing
- A sheet of lead or another weatherproof material that seals a joint in the roof, such as round a chimney or a panel bracket.
- G98 and G99
- The national processes for connecting generators to the network: G98 for small systems, notified after connection; G99 for larger ones, approved first.
- Gable
- The triangular end wall of a roof that is not hipped. A gable roof's main faces are rectangles, which take panels most easily.
- Hip
- The sloping edge where two roof faces meet at an outside corner. A hipped roof has faces that narrow towards the ridge, so fewer panels fit.
- Inverter
- The unit that turns the panels' direct current into the alternating current used in the house. Usually in the loft, garage or utility room.
- Isolator
- A switch that safely cuts the panels or the inverter off from the rest of the system, for maintenance or emergencies.
- kW and kWp
- A system's rated power. A quote for "4.4 kWp" means ten 440 W panels, for example.
- kWh
- A unit of energy, the thing electricity bills charge for and panels produce.
- Landscape and portrait
- Panels on their side (landscape) or upright (portrait). The planner tries both and shows the one that fits more.
- MCS
- The certification scheme for small renewable installations. An MCS certificate is needed for export tariffs and most grants.
- Microinverter
- A small inverter under each panel, used instead of one central inverter; useful on roofs with shade or several directions.
- Nail sickness
- Slates slipping because the nails holding them have corroded; common on old slate roofs and a sign that re-slating is due.
- Network operator
- The company that runs the local wires and must be told about every grid-connected system. In Southport, SP Energy Networks.
- Optimiser
- A device fitted to each panel that stops a shaded panel dragging down the output of the others.
- Permitted development
- Building work allowed without a planning application, within national limits. Most roof panels on houses in England qualify.
- Pitch
- The angle of a roof slope from horizontal. Southport's best for a south roof is about 41 degrees, according to PVGIS.
- PVGIS
- The European Commission's solar model, used throughout this site for output figures.
- Rafter
- One of the sloping timbers that form the roof frame. Every panel bracket must be fixed to one.
- Ridge
- The top edge of a roof, where the two main slopes meet. Panels must stay below the highest part of the roof.
- Slope length
- The distance from the gutter to the ridge measured along the roof. Half the house depth divided by the cosine of the pitch, for a ridge in the middle.
- Smart Export Guarantee (SEG)
- The rule that large electricity suppliers must offer a rate above zero for power you export from an MCS-certified system.
- Valley
- The inside corner where two roof slopes meet and water runs off; panels are kept clear of it.
- Verge
- The edge of a roof slope at a gable end.
Read on
Sources for this page
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