The acronyms, decoded.

From DNO offers to Scope 2 reporting, every acronym a commercial energy buyer is likely to meet — defined in plain English, with the numbers and rules of thumb our engineers actually use.

AC (Alternating Current): The form of electricity supplied by the grid and used by most building loads. Solar panels generate DC, which an inverter converts to AC for use on site.
AIC (Available Incoming Capacity): The kVA the local distribution network can physically deliver to a site, as opposed to MIC, which is the contractual import limit. New large loads (EV, process plant) are usually tested against both.
ANM (Active Network Management): A DNO scheme that curtails generation or load in real time during network constraint, in exchange for a faster and cheaper grid connection.
ASHP (Air Source Heat Pump): A heating system that extracts low-grade heat from outside air and upgrades it, typically delivering 3–4 kWh of heat per 1 kWh of electricity (a CoP of 3–4).
BESS (Battery Energy Storage System): A grid-tied lithium battery installation, usually packaged in a containerised or wall-mounted enclosure with its own inverter and battery management system.
BMS (Battery Management System): The electronic system that monitors and protects every cell in a battery — managing voltage, temperature, state of charge and balancing.
BREEAM: A sustainability assessment method for buildings. On-site renewables and energy strategy contribute directly to BREEAM Energy credits.
CAPEX (Capital Expenditure): The funding route in which the client buys the asset outright. Highest NPV in most cases but ties up capital and puts the asset on the balance sheet.
CDM Regulations 2015: UK Construction (Design and Management) Regulations governing health, safety and welfare on construction projects. Applies to almost all commercial PV work.
CfD (Contract for Difference): The UK government's main mechanism for supporting new large-scale low-carbon generation. Relevant for utility-scale projects, not typical commercial rooftop work.
CHP (Combined Heat and Power): A system that generates electricity and useful heat from the same fuel. Often the legacy asset that on-site solar or a heat pump replaces.
DC (Direct Current): The form of electricity produced by PV modules and stored in batteries. Converted to AC by an inverter before use on most building loads.
DC ratio (DC/AC ratio): The ratio of installed PV DC capacity to inverter AC capacity. A DC ratio of 1.2–1.3 is common in the UK to maximise inverter utilisation across cloudy conditions.
DNO (Distribution Network Operator): The licensed company that owns and operates the regional electricity distribution network — for example WPD / National Grid Electricity Distribution, UKPN, SSEN, Northern Powergrid.
DSEAR: The UK Dangerous Substances and Explosive Atmospheres Regulations. Relevant to battery storage design and risk assessment.
DSR (Demand Side Response): Paid services for shifting or reducing electricity demand at times of grid stress. Sites with flexible load or BESS can stack DSR revenue on top of self-consumption value.
EaaS (Energy-as-a-Service): A fully funded delivery model in which the provider designs, builds, owns and operates the energy assets, and the client pays a fixed unit rate (£/kWh) over 15–25 years. Zero CAPEX, single point of accountability.
Embodied carbon: The greenhouse-gas emissions associated with materials, manufacture, transport, construction and end-of-life of an asset — as opposed to its operational emissions.
EPC (Energy Performance Certificate): A regulatory rating (A–G) of a building's energy efficiency. Commercial lettings require a minimum EPC rating under MEES.
EPC (Engineering, Procurement & Construction): A single-contract turnkey delivery model in which one party takes responsibility for design, supply and installation. Not to be confused with an Energy Performance Certificate.
ESOS (Energy Savings Opportunity Scheme): A mandatory UK energy assessment scheme for large undertakings, run on a four-year cycle. From Phase 3 onward, qualifying organisations must publish an action plan and report progress.
Export limitation: Hardware and control logic, certified under ENA G100, that guarantees an installation will not export more than a contracted level to the grid. Often the key to unlocking a viable DNO offer on constrained networks.
FFR (Firm Frequency Response): A National Grid balancing service that pays asset operators to respond to grid frequency deviations. One of several revenue stacks available to commercial BESS.
FIT (Feed-in Tariff): The UK's pre-2019 export and generation tariff for small-scale renewables. Closed to new applicants in 2019; some legacy installations still benefit.
G100: ENA Engineering Recommendation governing certified export-limitation schemes. Lets a site install more on-site generation than its DNO export headroom would otherwise allow.
G98: ENA Engineering Recommendation governing connection of small generators (≤ 16 A per phase, roughly 3.68 kW single-phase). Notification only — no upfront DNO approval needed.
G99: ENA Engineering Recommendation governing connection of larger generators (> 16 A per phase). Requires a formal connection application to the DNO and an accepted offer before energisation.
GHG Protocol: The most widely used international standard for corporate greenhouse-gas accounting. Defines Scope 1, 2 and 3 emissions and the location-based and market-based methods for Scope 2.
Half-hourly data: Metered electricity consumption recorded every 30 minutes by an HH meter. The single most valuable input to a credible solar, battery or EV business case.
Inverter: The power-electronics device that converts DC from PV modules or batteries into grid-compatible AC. Typically the highest-failure-rate component in a PV system.
IRR (Internal Rate of Return): The discount rate at which an investment's net present value is zero. The most common headline financial metric for commercial solar and battery business cases.
ISO 9001 / 14001 / 45001 / 50001: International management-system standards for quality, environment, occupational health and safety, and energy management respectively. Together they form the backbone of a credible commercial energy contractor's compliance posture.
kVA (Kilovolt-ampere): The unit of apparent power. DNO connection capacity (MIC) is contracted in kVA, not kW.
kW (Kilowatt): The unit of real power — instantaneous rate of energy use or generation.
kWh (Kilowatt-hour): The unit of energy — 1 kW sustained for 1 hour. Electricity bills, generation forecasts and battery capacities are all denominated in kWh.
kWp (Kilowatt-peak): The nameplate DC capacity of a solar array under Standard Test Conditions (1000 W/m², 25 °C, AM 1.5). A 100 kWp UK rooftop typically generates 85,000–105,000 kWh per year.
LCOE (Levelised Cost of Energy): The total lifetime cost of an energy asset divided by the total lifetime energy it generates, in £/kWh. Useful for like-for-like comparison across funding routes and technologies.
LFP (Lithium Iron Phosphate): A lithium battery chemistry preferred for commercial stationary storage. More thermally stable and longer-cycle-life than NMC, at the cost of slightly lower energy density.
MCS (Microgeneration Certification Scheme): The UK quality-assurance scheme for low-carbon technologies. Required for systems that wish to claim the Smart Export Guarantee.
MIC (Maximum Import Capacity): The kVA a site is contractually allowed to import from the grid. Often the binding constraint when adding EV charging or process loads.
MPAN (Meter Point Administration Number): The unique 13-digit identifier for an electricity supply point in Great Britain. Required for every connection application and tariff comparison.
NPV (Net Present Value): The discounted sum of all future cashflows from a project, in today's money. Positive NPV means the project creates value at the chosen discount rate.
O&M (Operations & Maintenance): Ongoing monitoring, performance management, fault response and preventive maintenance of energy assets. Critical to securing long-term yield.
Optimiser (DC optimiser): A module-level power electronics device (e.g. SolarEdge) that maximises output from each panel independently. Particularly valuable on shaded or split-orientation roofs.
PAS 2080: The UK specification for managing whole-life carbon in buildings and infrastructure. Increasingly required on public-sector and large private contracts.
Passivhaus: An international low-energy building standard that combines fabric performance, airtightness and heat recovery to cut heating demand by ~90% versus a comparable conventional building.
Payback period: The number of years until cumulative savings or revenue equal the initial cost. Simple but ignores time value of money — use alongside IRR and NPV.
Performance ratio (PR): The ratio of actual to theoretical PV system output, accounting for losses (temperature, cables, inverter, soiling). A healthy commercial PV system runs at PR 78–85%.
PPA (Power Purchase Agreement): A contract under which a third party owns the on-site generation asset and the client pays only for the kWh generated, at a discount to grid. Zero CAPEX, fixed-or-indexed unit rate, typically 15–25 years.
PSDS (Public Sector Decarbonisation Scheme): A UK grant scheme funding decarbonisation projects in public-sector buildings — schools, NHS estate, local authorities. Run in oversubscribed phases.
PV (Photovoltaic): The technology that converts sunlight directly into electricity using semiconductor cells (almost always silicon, in commercial UK work).
REGO (Renewable Energy Guarantees of Origin): UK certificates evidencing that 1 MWh of electricity was generated from renewable sources. Underpins market-based renewable claims and green tariffs.
Salix Finance: Government-backed loan and grant body funding energy efficiency and decarbonisation in the UK public sector.
SBTi (Science Based Targets initiative): An international framework for setting corporate emissions-reduction targets aligned with the Paris Agreement. Increasingly the de-facto reference for credible net-zero plans.
Scope 1 / 2 / 3: GHG Protocol categories: Scope 1 is direct on-site emissions (gas, diesel), Scope 2 is purchased electricity and heat, Scope 3 is everything else in the value chain (supply chain, business travel, end-of-life).
SECR (Streamlined Energy and Carbon Reporting): UK regulation requiring large companies and LLPs to disclose UK energy use, associated emissions and at least one efficiency action in their annual report.
SEG (Smart Export Guarantee): The UK mechanism, since 2020, obliging licensed electricity suppliers (those with > 150,000 customers) to offer a tariff for exported small-scale renewable generation up to 5 MW.
Self-consumption: The share of on-site generation used on site rather than exported to the grid. In the UK, every kWh self-consumed is typically worth 3–6× more than every kWh exported.
Single-line diagram (SLD): The schematic electrical drawing showing the route from grid connection through protection, metering, inverters and loads. Required for every DNO application.
Smart meter: A meter that records and transmits energy consumption (and, in commercial settings, half-hourly data) without manual reads. The data backbone of credible energy decisions.
Solar thermal: Solar collectors that heat a fluid directly (typically water or glycol), as distinct from PV. Niche in commercial work today — usually superseded by PV + heat pump.
STC (Standard Test Conditions): The lab conditions (1000 W/m², 25 °C, AM 1.5) at which a PV module's nameplate kWp is rated. Real-world output is always lower than STC.
String inverter: An inverter that takes DC from a series-connected string of PV modules. The standard commercial topology, often paired with optimisers for shaded sites.
Three-phase supply: A grid supply delivering three alternating phases of AC. Standard on commercial sites and required for most inverters above ~11 kW and most EV rapid chargers.
TUoS / DUoS: Transmission Use of System and Distribution Use of System charges — the regulated costs of using the national and regional electricity networks, recovered through electricity bills.
UPS (Uninterruptible Power Supply): A system that delivers continuous power to critical loads through a grid outage. A correctly specified BESS can deliver UPS-grade behaviour as a side effect.
VPP (Virtual Power Plant): A cloud-orchestrated portfolio of distributed energy assets (PV, BESS, flexible load) operated together to deliver grid services and stacked revenue.
Ynni Cymru: The Welsh Government's publicly owned renewable energy company, used to fund community-owned and public-sector renewables in Wales.

By topic

Browse the same terms, grouped by topic.

Compliance & safety

CDM Regulations 2015 — UK Construction (Design and Management) Regulations governing health, safety and welfare on construction projects. Applies to almost all commercial PV work.
DSEAR — The UK Dangerous Substances and Explosive Atmospheres Regulations. Relevant to battery storage design and risk assessment.
MCS (Microgeneration Certification Scheme) — The UK quality-assurance scheme for low-carbon technologies. Required for systems that wish to claim the Smart Export Guarantee.

Delivery

EPC (Engineering, Procurement & Construction) — A single-contract turnkey delivery model in which one party takes responsibility for design, supply and installation. Not to be confused with an Energy Performance Certificate.
O&M (Operations & Maintenance) — Ongoing monitoring, performance management, fault response and preventive maintenance of energy assets. Critical to securing long-term yield.

Electrical

AC (Alternating Current) — The form of electricity supplied by the grid and used by most building loads. Solar panels generate DC, which an inverter converts to AC for use on site.
DC (Direct Current) — The form of electricity produced by PV modules and stored in batteries. Converted to AC by an inverter before use on most building loads.
Inverter — The power-electronics device that converts DC from PV modules or batteries into grid-compatible AC. Typically the highest-failure-rate component in a PV system.
kVA (Kilovolt-ampere) — The unit of apparent power. DNO connection capacity (MIC) is contracted in kVA, not kW.
kW (Kilowatt) — The unit of real power — instantaneous rate of energy use or generation.
kWh (Kilowatt-hour) — The unit of energy — 1 kW sustained for 1 hour. Electricity bills, generation forecasts and battery capacities are all denominated in kWh.
Single-line diagram (SLD) — The schematic electrical drawing showing the route from grid connection through protection, metering, inverters and loads. Required for every DNO application.
Three-phase supply — A grid supply delivering three alternating phases of AC. Standard on commercial sites and required for most inverters above ~11 kW and most EV rapid chargers.

Energy data

Half-hourly data — Metered electricity consumption recorded every 30 minutes by an HH meter. The single most valuable input to a credible solar, battery or EV business case.
MPAN (Meter Point Administration Number) — The unique 13-digit identifier for an electricity supply point in Great Britain. Required for every connection application and tariff comparison.
Smart meter — A meter that records and transmits energy consumption (and, in commercial settings, half-hourly data) without manual reads. The data backbone of credible energy decisions.

Finance

IRR (Internal Rate of Return) — The discount rate at which an investment's net present value is zero. The most common headline financial metric for commercial solar and battery business cases.
LCOE (Levelised Cost of Energy) — The total lifetime cost of an energy asset divided by the total lifetime energy it generates, in £/kWh. Useful for like-for-like comparison across funding routes and technologies.
NPV (Net Present Value) — The discounted sum of all future cashflows from a project, in today's money. Positive NPV means the project creates value at the chosen discount rate.
Payback period — The number of years until cumulative savings or revenue equal the initial cost. Simple but ignores time value of money — use alongside IRR and NPV.

Flexibility & markets

DSR (Demand Side Response) — Paid services for shifting or reducing electricity demand at times of grid stress. Sites with flexible load or BESS can stack DSR revenue on top of self-consumption value.
FFR (Firm Frequency Response) — A National Grid balancing service that pays asset operators to respond to grid frequency deviations. One of several revenue stacks available to commercial BESS.
VPP (Virtual Power Plant) — A cloud-orchestrated portfolio of distributed energy assets (PV, BESS, flexible load) operated together to deliver grid services and stacked revenue.

Funding

CAPEX (Capital Expenditure) — The funding route in which the client buys the asset outright. Highest NPV in most cases but ties up capital and puts the asset on the balance sheet.
CfD (Contract for Difference) — The UK government's main mechanism for supporting new large-scale low-carbon generation. Relevant for utility-scale projects, not typical commercial rooftop work.
EaaS (Energy-as-a-Service) — A fully funded delivery model in which the provider designs, builds, owns and operates the energy assets, and the client pays a fixed unit rate (£/kWh) over 15–25 years. Zero CAPEX, single point of accountability.
FIT (Feed-in Tariff) — The UK's pre-2019 export and generation tariff for small-scale renewables. Closed to new applicants in 2019; some legacy installations still benefit.
PPA (Power Purchase Agreement) — A contract under which a third party owns the on-site generation asset and the client pays only for the kWh generated, at a discount to grid. Zero CAPEX, fixed-or-indexed unit rate, typically 15–25 years.
PSDS (Public Sector Decarbonisation Scheme) — A UK grant scheme funding decarbonisation projects in public-sector buildings — schools, NHS estate, local authorities. Run in oversubscribed phases.
Salix Finance — Government-backed loan and grant body funding energy efficiency and decarbonisation in the UK public sector.
SEG (Smart Export Guarantee) — The UK mechanism, since 2020, obliging licensed electricity suppliers (those with > 150,000 customers) to offer a tariff for exported small-scale renewable generation up to 5 MW.
Ynni Cymru — The Welsh Government's publicly owned renewable energy company, used to fund community-owned and public-sector renewables in Wales.

Grid & DNO

AIC (Available Incoming Capacity) — The kVA the local distribution network can physically deliver to a site, as opposed to MIC, which is the contractual import limit. New large loads (EV, process plant) are usually tested against both.
ANM (Active Network Management) — A DNO scheme that curtails generation or load in real time during network constraint, in exchange for a faster and cheaper grid connection.
DNO (Distribution Network Operator) — The licensed company that owns and operates the regional electricity distribution network — for example WPD / National Grid Electricity Distribution, UKPN, SSEN, Northern Powergrid.
Export limitation — Hardware and control logic, certified under ENA G100, that guarantees an installation will not export more than a contracted level to the grid. Often the key to unlocking a viable DNO offer on constrained networks.
G100 — ENA Engineering Recommendation governing certified export-limitation schemes. Lets a site install more on-site generation than its DNO export headroom would otherwise allow.
G98 — ENA Engineering Recommendation governing connection of small generators (≤ 16 A per phase, roughly 3.68 kW single-phase). Notification only — no upfront DNO approval needed.
G99 — ENA Engineering Recommendation governing connection of larger generators (> 16 A per phase). Requires a formal connection application to the DNO and an accepted offer before energisation.
MIC (Maximum Import Capacity) — The kVA a site is contractually allowed to import from the grid. Often the binding constraint when adding EV charging or process loads.
TUoS / DUoS — Transmission Use of System and Distribution Use of System charges — the regulated costs of using the national and regional electricity networks, recovered through electricity bills.

Heat & buildings

ASHP (Air Source Heat Pump) — A heating system that extracts low-grade heat from outside air and upgrades it, typically delivering 3–4 kWh of heat per 1 kWh of electricity (a CoP of 3–4).
CHP (Combined Heat and Power) — A system that generates electricity and useful heat from the same fuel. Often the legacy asset that on-site solar or a heat pump replaces.
Passivhaus — An international low-energy building standard that combines fabric performance, airtightness and heat recovery to cut heating demand by ~90% versus a comparable conventional building.
Solar thermal — Solar collectors that heat a fluid directly (typically water or glycol), as distinct from PV. Niche in commercial work today — usually superseded by PV + heat pump.

Reporting & standards

BREEAM — A sustainability assessment method for buildings. On-site renewables and energy strategy contribute directly to BREEAM Energy credits.
Embodied carbon — The greenhouse-gas emissions associated with materials, manufacture, transport, construction and end-of-life of an asset — as opposed to its operational emissions.
EPC (Energy Performance Certificate) — A regulatory rating (A–G) of a building's energy efficiency. Commercial lettings require a minimum EPC rating under MEES.
ESOS (Energy Savings Opportunity Scheme) — A mandatory UK energy assessment scheme for large undertakings, run on a four-year cycle. From Phase 3 onward, qualifying organisations must publish an action plan and report progress.
GHG Protocol — The most widely used international standard for corporate greenhouse-gas accounting. Defines Scope 1, 2 and 3 emissions and the location-based and market-based methods for Scope 2.
ISO 9001 / 14001 / 45001 / 50001 — International management-system standards for quality, environment, occupational health and safety, and energy management respectively. Together they form the backbone of a credible commercial energy contractor's compliance posture.
PAS 2080 — The UK specification for managing whole-life carbon in buildings and infrastructure. Increasingly required on public-sector and large private contracts.
REGO (Renewable Energy Guarantees of Origin) — UK certificates evidencing that 1 MWh of electricity was generated from renewable sources. Underpins market-based renewable claims and green tariffs.
SBTi (Science Based Targets initiative) — An international framework for setting corporate emissions-reduction targets aligned with the Paris Agreement. Increasingly the de-facto reference for credible net-zero plans.
Scope 1 / 2 / 3 — GHG Protocol categories: Scope 1 is direct on-site emissions (gas, diesel), Scope 2 is purchased electricity and heat, Scope 3 is everything else in the value chain (supply chain, business travel, end-of-life).
SECR (Streamlined Energy and Carbon Reporting) — UK regulation requiring large companies and LLPs to disclose UK energy use, associated emissions and at least one efficiency action in their annual report.

Solar PV

DC ratio (DC/AC ratio) — The ratio of installed PV DC capacity to inverter AC capacity. A DC ratio of 1.2–1.3 is common in the UK to maximise inverter utilisation across cloudy conditions.
kWp (Kilowatt-peak) — The nameplate DC capacity of a solar array under Standard Test Conditions (1000 W/m², 25 °C, AM 1.5). A 100 kWp UK rooftop typically generates 85,000–105,000 kWh per year.
Optimiser (DC optimiser) — A module-level power electronics device (e.g. SolarEdge) that maximises output from each panel independently. Particularly valuable on shaded or split-orientation roofs.
Performance ratio (PR) — The ratio of actual to theoretical PV system output, accounting for losses (temperature, cables, inverter, soiling). A healthy commercial PV system runs at PR 78–85%.
PV (Photovoltaic) — The technology that converts sunlight directly into electricity using semiconductor cells (almost always silicon, in commercial UK work).
Self-consumption — The share of on-site generation used on site rather than exported to the grid. In the UK, every kWh self-consumed is typically worth 3–6× more than every kWh exported.
STC (Standard Test Conditions) — The lab conditions (1000 W/m², 25 °C, AM 1.5) at which a PV module's nameplate kWp is rated. Real-world output is always lower than STC.
String inverter — An inverter that takes DC from a series-connected string of PV modules. The standard commercial topology, often paired with optimisers for shaded sites.

Storage

BESS (Battery Energy Storage System) — A grid-tied lithium battery installation, usually packaged in a containerised or wall-mounted enclosure with its own inverter and battery management system.
BMS (Battery Management System) — The electronic system that monitors and protects every cell in a battery — managing voltage, temperature, state of charge and balancing.
LFP (Lithium Iron Phosphate) — A lithium battery chemistry preferred for commercial stationary storage. More thermally stable and longer-cycle-life than NMC, at the cost of slightly lower energy density.
UPS (Uninterruptible Power Supply) — A system that delivers continuous power to critical loads through a grid outage. A correctly specified BESS can deliver UPS-grade behaviour as a side effect.

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