- AC (Alternating Current)
- Electricity that reverses direction periodically. UK mains electricity is AC at 230 volts and 50 hertz. Homes are wired for AC. Solar systems produce AC via an inverter. See AC vs DC.
- DC (Direct Current)
- Electricity flowing in one constant direction. Solar panels produce DC. Batteries charge and discharge using DC.
- PV (Photovoltaic)
- Relating to the conversion of light into electricity. Solar PV panels use the photovoltaic effect to generate power. Distinct from solar thermal, which heats water.
- Photovoltaic Effect
- The physical process by which photons from sunlight free electrons in a semiconductor (typically silicon), creating an electric current. The fundamental principle behind all solar panels.
- Inverter
- A device that converts DC electricity from solar panels into AC electricity for household use and grid synchronisation. Essential in every grid-connected solar system.
- Hybrid Inverter
- An inverter that combines solar DC-to-AC conversion with battery charge and discharge management in a single unit. Used in systems with battery storage.
- String Inverter
- A central inverter serving one or more strings of panels wired in series. The most common inverter type for uncomplicated roof layouts.
- Microinverter
- A small inverter mounted at each panel (or pair), converting DC to AC individually. Can improve performance on partially shaded or multi-orientation roofs.
- Optimiser
- A device attached to an individual panel allowing it to operate at its own maximum power point, mitigating shading losses in string systems.
- kW (Kilowatt)
- A unit of power equal to 1,000 watts. Solar systems are rated in kW (e.g. a 4 kW system). EV chargers and battery inverters are also rated in kW, indicating maximum power output at any instant.
- kWh (Kilowatt-hour)
- A unit of energy equal to 1,000 watt-hours. Electricity consumption and generation are measured in kWh. Your electricity bill and solar generation totals are expressed in kWh. Battery capacity is also measured in kWh.
- Power
- The rate at which electricity is generated or consumed at a given moment, measured in watts or kilowatts. Power describes capacity in an instant, for example how many kW an inverter or EV charger can deliver right now.
- Energy
- The total amount of electricity generated, stored or consumed over a period of time, measured in kilowatt-hours. Energy is power multiplied by time; a 3 kW system running for two hours produces 6 kWh of energy.
- Import
- Drawing electricity from the national grid to meet household demand when solar generation and any battery storage are insufficient. The opposite of export.
- Export
- Sending surplus solar-generated electricity to the national grid when generation exceeds household demand and battery capacity. Recorded by a smart or export meter. See exporting to the grid.
- Export Meter
- A meter, often integrated within a smart meter, that specifically records the volume of electricity exported to the grid. Used as the basis for any export tariff payments.
- Self-Consumption
- Using solar-generated electricity within your home rather than exporting it. Typically provides more value than export because it avoids buying electricity at the import rate.
- Battery Capacity
- The total amount of energy a home battery can store, measured in kWh. Usable capacity may be less than the nominal figure due to depth of discharge limits.
- Usable Capacity
- The proportion of a battery's nominal capacity that can actually be discharged in practice, after accounting for depth of discharge limits set to protect the battery's lifespan.
- Depth of Discharge (DoD)
- The percentage of a battery's capacity that has been used. Batteries are typically not discharged to 100% to preserve lifespan. A 10 kWh battery with 90% DoD has 9 kWh of usable capacity.
- Cycle Life
- The approximate number of charge and discharge cycles a battery can complete before its usable capacity falls below a specified level. Cycle life varies by battery chemistry and how the battery is used.
- Smart Meter
- A digital electricity meter that records import and export in near real time. Required for accurate billing and export tariff arrangements. Most UK smart meters support half-hourly readings.
- Grid
- The national electricity distribution network. Grid-connected solar systems import from the grid when generation is insufficient and export surplus when generation exceeds demand.
- EV Charger
- A dedicated charge point for electric vehicles, connected to the home's electrical system. Smart chargers can integrate with solar systems to prioritise solar energy. See solar with EV charging.
- Solar Diversion
- Automatically directing available solar surplus toward a specific load, such as an EV charger or immersion heater, rather than exporting it to the grid. Availability depends on the equipment installed.
- Load
- Any device or circuit drawing electricity, such as an appliance, EV charger or heat pump. Total household load at a given moment determines how much demand solar, battery and grid supply must meet together.
- Load Management
- Systems that balance electricity demand across multiple loads (solar, battery, EV charger, heat pump) to avoid overloading the supply and maximise solar utilisation.
- Clipping
- When panel output momentarily exceeds an inverter's maximum capacity, so the surplus above that limit is not converted. A modest amount of clipping is often an accepted design trade-off for cost efficiency.
- MPPT (Maximum Power Point Tracking)
- The method inverters use to continuously adjust and extract the maximum available power from solar panels as sunlight, temperature and shading conditions change throughout the day.
- Shading
- Obstruction of sunlight reaching panels by trees, buildings, chimneys or other objects. Even partial shading can significantly reduce output. See efficiency and shading.
- Orientation
- The compass direction a roof surface faces. South-facing is generally optimal in the UK. East and west orientations produce less total annual energy but different daily timing profiles.
- Roof Pitch
- The angle of a roof surface relative to horizontal. Pitch affects how directly sunlight strikes a panel and interacts with orientation and season to determine performance. See efficiency and orientation.
- Efficiency
- For panels: the percentage of sunlight converted to electricity (typically 19-22% for modern residential panels). For inverters: the percentage of DC input successfully converted to AC output (typically 96-98%).
Understand Your Property's Solar Suitability
If you understand the basics and want your own property assessed, you can book a technical solar review. Suitability depends on the property, roof, shading, usage and tariff - subject to survey.
Book a Technical Solar Review