Precise, 2-to-4 sentence definitions for every solar, battery, grid and tariff term used on this site. Each entry links directly to its primary guide.
DC coupling connects solar panels and batteries on the same DC bus before the inverter. AC coupling retrofits a battery with its own inverter to the existing house AC wiring. DC coupling is slightly more efficient; AC coupling is easier to add to existing solar setups.
An algorithmic model used in California (NEM 3.0) to calculate the hourly avoided wholesale energy, capacity, and environmental cost for grid export credits across 8,760 hours a year.
The compass direction a solar roof faces, measured in degrees from true North (0°) or South (180°). In the northern hemisphere, true South facing roofs achieve maximum annual kWh output.
A protective diode wired across a sub-string of cells in a solar panel. When one cell is shaded, the bypass diode routes current around the affected section, preventing hotspots and preserving output from the unshaded sub-strings.
The ratio of solar panel DC rating to inverter AC output capacity. An oversourced DC ratio (e.g. 1.25:1) maximizes morning and evening production while clipping peak mid-day generation that exceeds inverter capacity.
The gradual decline in a solar panel’s output capacity over time. Premium monocrystalline panels degrade by roughly 0.3% to 0.5% per year, retaining over 85% of rated power after 25 years.
The percentage of total battery capacity that can be safely discharged. Modern LFP batteries offer 90% to 100% usable DoD without accelerating chemical degradation.
Direct light travels straight from the sun without scattering. Diffuse light is sunlight scattered by clouds, dust, and atmosphere. Solar panels generate power from both, which is why yield continues on overcast days.
A metric measuring battery usage by summing partial charge and discharge events into equivalent 100% discharges. Most battery warranties warrant 4,000 to 6,000 EFC over a 10-year period.
UK Distribution Network Operator (DNO) regulations. G98 applies to standard micro-generators up to 16A per phase (3.68 kW single phase). G99 requires formal prior permission for larger inverter systems.
Settlement process where smart meters record electricity consumption and export in 30-minute blocks, enabling dynamic smart tariffs that change rates throughout the day based on wholesale energy markets.
An inverter capable of managing inputs from both solar PV panels and a home battery storage system simultaneously, eliminating the need for a separate battery inverter.
Irradiance is the instantaneous power density of sunlight hitting a surface (measured in W/m²). Insolation is the cumulative solar energy received over a timeframe (measured in kWh/m² per day or year).
A unit of energy equal to 1,000 watts delivered or consumed over one hour. Solar yield is measured in kWh per year, and domestic electricity bills are billed per kWh.
The nominal maximum power output of a solar panel array under Standard Test Conditions (STC: 1,000 W/m² irradiance, 25°C cell temperature). Real-world peak output is typically 10–20% lower due to heat and atmospheric losses.
A battery chemistry (LiFePO4) favored in modern residential storage for its thermal stability, safety profile, long cycle life (6,000+ cycles), and non-use of cobalt.
A small loss in panel efficiency (typically 1% to 3%) occurring within the first few hours or days of sunlight exposure due to boron-oxygen complex formation in silicon cells.
The standards organization in Great Britain certifying renewable energy products and installers. MCS installation certification is required to qualify for SEG export tariffs and local grant schemes.
A small inverter mounted directly behind an individual solar panel, converting DC to AC at the module level. Allows independent MPPT optimization per panel, eliminating single-panel shading penalties across the rest of the array.
An electronic algorithm used by inverters to continuously adjust voltage and current, ensuring the solar array operates at its peak electrical output under changing light levels.
California’s Net Billing Tariff adopted under CPUC Decision 22-12-056. Replaced 1-to-1 net metering with Avoided Cost Calculator values, reducing average export credit values by ~75% and incentivizing battery storage.
Nominal Operating Cell Temperature (or Nominal Module Operating Temperature). The temperature a solar cell reaches under realistic ambient conditions (800 W/m² irradiance, 20°C air temp, 1 m/s wind). Typically 43°C to 47°C.
The legal maximum unit rate (p/kWh) and standing charge (p/day) that energy suppliers can charge domestic customers on standard variable tariffs in Great Britain, reviewed quarterly by regulator Ofgem.
A degradation phenomenon caused by stray voltage leakage between silicon cells and the grounded metal frame, worsened by high humidity and heat. Modern quality panels use PID-resistant materials.
A module-level DC-to-DC converter fitted to individual panels. It optimizes MPPT per panel while sending DC power to a central string inverter, combining panel-level monitoring with central inversion.
The percentage of energy retrieved from a battery relative to the energy supplied to charge it. Domestic battery systems typically achieve 85% to 92% round-trip efficiency accounting for inverter and thermal losses.
The Dutch net metering scheme allowing households to offset annual exported solar energy 1-to-1 against grid import kWh. Scheduled for complete phase-out on 1 January 2027.
The UK government-mandated scheme requiring licensed energy suppliers with over 150,000 customers to offer a payment rate per kWh for renewable electricity exported to the grid by homeowners.
The fraction of total solar generation consumed on-site by home loads or stored in a battery, rather than exported to the grid. Higher self-consumption increases solar ROI when export tariffs are lower than import prices.
Yield reduction caused by dust, pollen, bird droppings, and soot accumulating on glass surfaces. In temperate climates with regular rain, ambient soiling losses stay below 2% to 4% annually.
A fixed daily fee (pence per day) charged by energy suppliers regardless of how much electricity or gas is consumed, covering grid maintenance, metering, and supplier operating costs.
Laboratory rating conditions for solar panels: 1,000 W/m² irradiance, 25°C cell temperature, and air mass 1.5 spectrum. Because real cells run much warmer outdoors, STC power ratings exceed typical field performance.
A single central inverter that converts DC electricity from a series-connected row (string) of solar panels into household AC electricity. Simple and reliable, but performance can be bottlenecked if one panel in the string is heavily shaded.
The percentage drop in solar panel power output for every degree Celsius above 25°C. Modern silicon panels lose approximately 0.30% to 0.40% of peak power per °C of heating.
Fees introduced by Dutch energy suppliers charging solar owners for feeding excess power back onto the grid during negative or low wholesale price windows.
The angle of solar panels relative to the horizontal ground. The optimal tilt for maximum annual yield in northern Europe is typically between 30° and 40°.
Nominal capacity is the total energy stored chemically in a battery (e.g. 10 kWh). Usable capacity is the net energy available to power household loads (e.g. 9.5 kWh) after depth-of-discharge margins.