Solar Panel Installer Runcorn, an independent guide › Choosing
Solar words, explained
Flat-roof solar brings its own vocabulary on top of the usual electrical and roofing words. These are the terms you will meet on a Runcorn survey or quote.
Checked against its sources on 3 November 2026. Published by SEO Dons; we do not supply or install solar.
- Ballast
- Weight, usually concrete blocks, that holds a flat-roof frame down against the wind without fixing through the roof covering.
- Ballasted frame
- A frame for panels on a flat roof that is held in place by ballast rather than bolted to the roof.
- East-west array
- Pairs of low-tilted panels back to back, one facing east and one west, like a row of low tents.
- Flat-roof covering
- The waterproof layer on a flat roof: felt, asphalt, single-ply membrane or similar. It must be sound before panels go on.
- Ground cover ratio
- The share of a flat roof covered by panels seen from above. Steeper tilts need wider row spacing and cover less.
- Inter-row spacing
- The gap left behind each row of tilted panels so that it does not shade the next row when the sun is low.
- Permitted development (flat roof)
- On a house, an array on a flat roof needs no planning application if no part stands more than 0.6 m above the roof, among other conditions.
- Tilt
- The angle of the panels from horizontal. On flat roofs it is chosen; on pitched roofs it is the roof pitch.
- Upstand
- The raised edge of a flat roof or the kerb round a rooflight; frames must keep clear of it.
- Pitch
- The slope of a pitched roof from horizontal.
- Rafter / truss
- The timbers that form a pitched roof; brackets for panels are fixed to them.
- Rail
- The aluminium bar the panels clamp to, on brackets (pitched roofs) or frames (flat roofs).
- Inverter
- Turns the panels' direct current into the alternating current the house uses.
- Isolator
- A switch to cut off the panels or the inverter safely.
- G98 / G99
- How a home generator joins the network: connect then notify for small systems; apply first for larger ones.
- Export limit
- A setting that caps how much the system can send to the grid at once, sometimes a condition of G99 approval.
- kWp
- The rated power of a set of panels. Eleven 440 W panels make 4.84 kWp.
- kWh
- A unit of energy: what bills charge for and panels produce.
- MCS
- The certification scheme for small renewable installations, needed for export payments and most grants and loans.
- MIS 3002
- MCS's installation standard for solar PV. Version 6.0 (March 2026) asks for panels to be kept 400 mm from any edge of a home's roof unless specific measures are taken.
- PVGIS
- The European Commission's solar output model, used for this site's output figures.
- Shade factor
- The figure by which an installer reduces predicted output for shade; 1 means none.
- Export tariff
- What a supplier pays for each unit you send to the grid; large suppliers must offer one for MCS-certified systems.
- Conservation area
- An area protected for its character; in one, a flat-roof array needs the council's prior approval.
Keep reading
Where the figures come from
- Legislation.gov.uk: GPDO 2015 Schedule 2 Part 14 (solar on homes)
- Legislation.gov.uk: SI 2026/896, solar permitted development changes (27 August 2026)
- MCS: The Solar PV Standard (Installation), MIS 3002 v6.0
- SP Energy Networks: getting connected
- EU JRC PVGIS 5.3: solar output by location, tilt and direction
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