Liverpool Solar Glossary: Planning, Roofs, the Grid

Article 4 direction: A council order that withdraws certain permitted-development rights in an area. In Liverpool they cover most conservation areas and include roof alterations. More on this
Conservation area: A district the council protects for its historic character; Liverpool has 36. More on this
Listed building: A building protected on Historic England's national list; Liverpool has 1,527 entries, and any panels on one need listed building consent. More on this
Permitted development: Building work that needs no planning application because national rules already allow it, as long as it stays inside set limits; panels on a house roof usually count. More on this
Parapet: A low wall along the front edge of a roof, common on Georgian terraces, which can hide the roof from the street. More on this
Valley roof: A roof with two slopes falling inwards to a central gutter, sometimes found behind a parapet. More on this
Offshoot: The narrow rear extension of many Victorian terraces, which can shade the main back slope. More on this
Through-terrace: The usual Liverpool terrace: rooms front and back, a yard behind, and both halves of the roof belonging to the house. More on this
SP Energy Networks: The company that runs the local electricity network in Liverpool, Merseyside, Cheshire and North Wales. More on this
G98: The connection standard for small generators up to 16 A per phase (3.68 kW single-phase), where the network is told rather than asked. More on this
G99: The route for bigger installations, where SP Energy Networks studies the proposal and has to say yes before anything is switched on. More on this
Commissioning: The moment the finished system is tested and switched on; for a small system the network must have been told by then.
Warm Homes: Local Grant: The government-funded grant for lower-income households, run in Liverpool by the city council, with postcode, benefit and income (under £36,000) pathways. More on this
Indices of Multiple Deprivation: The official ranking of small areas in England by deprivation; the two most deprived tenths form one route into the council grant. More on this
Solar Together: A group-buying scheme run in rounds for the Liverpool City Region, where installers bid to supply registered households. More on this
EPC: The Energy Performance Certificate, which grades a home from A (most efficient) to G; the council scheme looks for D to G. More on this
Optimiser: A box fitted behind each panel so that one panel in shade, say from a chimney stack, does not drag down the output of the others. More on this
Export limiting: A setting or device that keeps the power sent out to the network below an agreed ceiling, sometimes used to stay within a connection limit. More on this
kW and kWh: Kilowatts (kW) describe how big a system is; kilowatt-hours (kWh) count the electricity it produces. Each kW facing south in central Liverpool gives roughly 965 kWh in a year. More on this
PVGIS: The solar calculator built by the European Commission's Joint Research Centre; all the output numbers on this site come from it. More on this
MCS: The certification scheme for small-scale renewable installers and products; your system's MCS certificate is what a supplier asks for before paying for exports. More on this
Export rate: The price per kWh a supplier offers for the surplus electricity your panels feed into the grid. More on this
Plug-in solar: Balcony-sized kits that connect through an ordinary socket, allowed up to 800 W under the 2026 regulations. More on this

Liverpool solar glossary

Where the facts come from

Further reading

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