Glossary of terms

A guide to common terms used in the green home, home efficiency, and renewables sectors.

ASHP (Air Source Heat Pump)

A system which transfers heat from the outside air to water, which heats your rooms via radiators or underfloor heating.

BUS (Boiler Upgrade Scheme)

A government grant of £7,500 to help with the upfront cost of installing a heat pump.

DNO (Distribution Network Operator)

The company that owns and operates the power lines and infrastructure that connect your home to the grid. You often need their permission to install large heat pumps or EV chargers.

ECO4 (Energy Company Obligation)

A government energy efficiency scheme in Great Britain to help reduce carbon emissions and tackle fuel poverty.

EPC (Energy Performance Certificate)

A document that shows how energy efficient a property is, rated from A (most efficient) to G (least efficient).

GBIS (Great British Insulation Scheme)

A government scheme providing single-measure insulation improvements for a wider range of households than ECO4.

GSHP (Ground Source Heat Pump)

A system that extracts heat from the ground through pipes buried in your garden, which can then be used to heat your home.

MCS (Microgeneration Certification Scheme)

A quality assurance scheme which certifies low-carbon energy technologies and installers. Most grants require using an MCS-certified installer.

REGO (Renewable Energy Guarantees of Origin)

A certificate that proves a unit of electricity was generated from a renewable source.

Retrofit Coordinator

A professional responsible for overseeing home energy improvements to ensure they are safe, effective, and follow the PAS 2035 standard.

SAP (Standard Assessment Procedure)

The government’s method for assessing and comparing the energy and environmental performance of dwellings.

SEG (Smart Export Guarantee)

A government-backed initiative that requires some electricity suppliers to pay small-scale generators for low-carbon electricity they export back to the National Grid.

Thermal Bridge

An area of a building which has significantly higher heat transfer than the surrounding materials, such as where a solid wall meets a floor.

TOU (Time of Use Tariff)

An electricity tariff where the price you pay per kWh changes depending on the time of day, often cheaper at night or during periods of high renewable generation.

TRV (Thermostatic Radiator Valve)

A self-regulating valve fitted to hot water heating system radiators to control the temperature of a room by changing the flow of hot water to the radiator.

U-value

A measure of the rate of heat loss through a building component (like a wall or window). A lower U-value means better insulation.

V2G (Vehicle-to-Grid)

A technology that allows electric vehicle batteries to discharge electricity back into the grid or your home.