Solar Panel Installer St Helens (solar for St Helens homes) / Choosing
Solar jargon, explained
Surveys and quotes use words from three trades: solar design, roofing and electrics. These are the ones you will meet most on a St Helens roof, starting with the shade words.
Sources read on 3 November 2026. Published by SEO Dons, which runs this St Helens site.
- Altitude (of the sun)
- How high the sun is above the horizon, in degrees. Over St Helens it reaches about 60 at midday in June and about 13 in December.
- Azimuth
- The compass direction of the sun, or of a roof, measured clockwise from north: 90 is east, 180 south, 270 west.
- Bypass diode
- A component inside a panel that lets current skip a shaded section, so the whole panel does not shut down.
- Near shade
- In MCS's guidance, shade from an object 10 m or less from the array, such as a chimney or vent pipe. It is assessed more cautiously than distant shade.
- Shade factor (SF)
- The figure, from 0 to 1, by which an installer reduces the predicted output for shade. 1 means no shade.
- Sun-path diagram
- A chart of the sun's track across the sky through the year, on which an installer draws the outline of obstacles to work out the shade factor.
- String
- A set of panels wired in series to one inverter input. The current through a string is limited by its weakest panel.
- Optimiser
- A small device under a panel that lets it work at its own best point, so shade on it does not hold back the string.
- Microinverter
- A small inverter under each panel, used instead of one central inverter.
- MPPT
- Maximum power point tracking: how an inverter finds the best working point for a string. Inverters with two MPPT inputs can handle two directions or a shaded group separately.
- Inverter
- Converts the panels' direct current into the alternating current used in the house.
- Outrigger
- A narrower rear wing on a terraced or semi-detached house, usually with its own lower roof.
- Party wall
- The wall shared with the house next door. Work that affects it may fall under the Party Wall etc. Act 1996.
- Pitch
- The angle of a roof slope from horizontal.
- Stack
- A chimney stack: the brick structure on or through the roof that carries flues. On terraces it is often shared between neighbours.
- Article 4 direction
- A council order removing some permitted development rights in a defined area, so certain changes need an application.
- Conservation area
- An area protected for its character. St Helens has eight.
- Permitted development
- Work allowed without a planning application within national conditions. Most roof panels on houses qualify.
- G98 / G99
- The two routes for connecting a generator to the network: notify after connecting (small systems) or apply first (larger ones).
- kWp
- A system's rated power under test conditions. A "3.5 kWp" system might be eight panels of about 440 W.
- kWh
- A unit of energy, what bills charge for and panels produce.
- MCS
- The certification scheme for small renewable installations; its certificate is needed for export payments and most grants and loans.
- PVGIS
- The European Commission's solar output model, used for this site's output figures.
- Export tariff
- What a supplier pays you for each unit your system sends to the grid. Large suppliers must offer one for MCS-certified systems.
Related pages
References
- MCS MGD 005: solar PV shade evaluation procedure (shade factor)
- MCS MIS 3002 version 6.0: the solar PV installation standard
- Town and Country Planning (General Permitted Development) Order 2015, Schedule 2 Part 14
- SP Energy Networks: generation connections
- PVGIS 5.3 photovoltaic estimates (EU Joint Research Centre)
Get a solar quote for your St Helens roof, shade and all
Tell us what you would like a quote for, with your St Helens postcode and what stands to the south of the roof: a stack, the houses opposite or a tree. Your details go to SEO-DONS LTD, publisher of Solar Panel Installer St Helens, and we reply by email.
What happens next
- Send the form: it reaches SEO-DONS LTD, and a full postcode tells us which part of the borough you are in.
- We read it and reply by email, with the figures and sources that apply to you.
- Asking for a quote costs nothing, and whether and with whom you go ahead is your decision.