0800 043 0151
Power Heat Water Home

Jargon Buster

Do you know your Energy Efficiency from your ECO? Your Smart Meter from your storage heater? Read on for our jargon busting list of terms you might come across in this site and others. Or if you need to know about something, get in touch with our Save Energy Advice line, by phone or email, here.



  • Cavity Wall
    External wall made of two layers with a gap (or cavity) between. Most homes built since the 1920's have outside cavity walls.
  • Collective Switch
  • Condensing Boiler
    A more efficient boiler that uses the waste heat in the flue gases is used to pre-heat cold water entering the boiler. Most new boilers in the UK are condensing.


  • Draughts
    Uncontrolled ventilation, and also a cause of considerable heat loss.


  • Energy Company Obligation (ECO)
    Runs alongside the Green Deal with the twin aims of reducing domestic carbon emissions and alleviating fuel poverty. It will be delivered by the larger energy companies (any with more than 250,000 customers) and they are expected to invest £1.3bn a year (which they are expected to recoup through energy bills).
  • Energy Performance Certificate (EPC)
    EPCs rate your house (or business premises) for energy efficiency on a scale of A to G. It also provides information on how to improve the energy efficiency, and what level you would attain if you put the measures in place. All homes bought, sold or rented require an EPC.


  • Fuel Poverty


  • Green Deal
    A pay as you save scheme for energy efficiency measures introduced in October 2012. It is available for domestic, business, and for landlords.
  • Green Deal Advisor (GDA)
    The person who comes to your home or business to do the assessment. They may be independent, or employed by a GDP (see below). The latter may also have a sales role. If they want to try to sell you any of the measures recommended in the green deal advice report, they must ask your permission before starting the assessment.
  • Green Deal Assessment
    Before you can access green deal finance, you must have an assessment. This starts with an EPC, then the advisor will ask you about your energy use to generate a green deal advice report that is tailored to how you live.
  • Green Deal Assessor Organisation (GDAO)
    Start here if you want a green deal assessment done. They range from one man bands to co-operatives to large organisations. Some are also a green deal provider.
  • Green Deal Cashback Scheme
    An offer where households in England and Wales can claim Cashback on energy saving improvements like insulation, front doors, windows and boilers, whether or not you use the green deal finance, as long as you have a green deal assessment and get and agree quotes through a green deal provider.
  • Green Deal Installer
    Someone who is accredited to install one or more green deal measures.
  • Green Deal Provider
    Arranges Green Deal Plans, provides finance, and arranges for the installation of the agreed energy efficiency improvements through an authorised Installer. Green Deal providers must become authorised and operate to a high standard.


  • Heat Pumps


  • Immersion Heaters
    In a home without a boiler, water can be heated using one or more immersion heaters which heat water in the cylinder, usually one in the top and one in the bottom. Immersion heaters are commonly used in night-storage heaters, and also can be used to heat water from solar PV.


  • kWh
    Kilowatt hour is a unit used to measure energy. Electricity bills are charged in kilowatt hours, and it is the unit used to measure the energy generated by wind turbines or photovoltaic solar panels.


  • Low Carbon Energy
    This term refers to technologies which minimise the amount of carbon (or greenhouse gas) emitted into the atmosphere. At a domestic level it includes air and ground source heat pumps and combined heat and power. In national terms it includes nuclear power or the yet to be developed concept of carbon capture and storage, both of which continue to be controversial.


  • Programmer
    This is where you can set the on/off times for your heating and hot water. It's worth making sure that you can control the heating and hot water separately if you are thinking of installing solar water heating.


  • Renewable Energy
    Energy generated from sustainable natural resources, such as sun, wind, water and geothermal heat. This includes biogas and biomass, hydroelectricity, solar heat and electricity, geothermal energy, wind, wave and tidal power.
  • Retro-fit
    Refers to products that are installed to an existing house, rather than as part of a new build. It tends to be more expensive to retro-fit, as systems such as plumbing might have to be changed.
  • Room Thermostat
    Turns the boiler (and thus the heating) on when the temperature falls below the required temperature and off when it rises above it. It should be placed in the most used room. Digital thermostats are much more accurate than the older dial type.


  • Safe & Warm Campaign
    Wirral Council has a single point of contact for residents who are struggling with colder temperatures or snowy weather conditions: 0151 691 8448 or staywarm@wirral.gov.uk
  • SAP
    The Standard Assessment Procedure is the Government's principal methodology for assessing the energy and environmental performance and the compliance of new and existing dwellings.
  • Smart Meter
    Records consumption of electricity (or can be for gas or water) at short intervals and allows two way communication about that information between the user and the utility supplier. They allow for real-time awareness of electricity usage and cost, as well as remote control of electricity use.
  • Solid Wall
    Unlike cavity walls, which are composed to two layers of wall with a gap between, solid walls have no gap. Homes built pre-1920's will probably have solid outside walls. Solid walls let more heat out, so although they tend to cost more to insulate, solid wall insulation will save a lot of energy from heating.
  • Storage Heater
    A heater that is designed to take advantage of cheaper night-time electricity tariffs and release heat later into the home. These generally need to be topped up during the day, and are not a very efficient way form of heating.
  • Suspended FloorThis is where floorboards are laid on joists. A good way to tell whether you have got these is by looking to see if you have airbricks outside.


  • The Green Deal Finance Company (TGDFC)
    A non for profit company made up from more than 50 members from public and private sectors, set up to make finance available to all accredited Green Deal Providers.
  • Thermostatic Radiator Valves (TRV)
    These are the most basic form of zone control. Fitted to individual radiators, they allowing you to control the heat in each room. The radiator in the room with the room thermostat should not have a TRV as well. To be effective they need a free flow of air to sense the temperature in the room, so shouldn't be obstructed by furniture or curtains.
  • Tog Valve
    These are the most basic form of zone control. Fitted to individual radiators, they allowing you to control the heat in each room. The radiator in the room with the room thermostat should not have a TRV as well. To be effective they need a free flow of air to sense the temperature in the room, so shouldn't be obstructed by furniture or curtains.


  • Underfloor Heating
    A heating system using either warm water piped under the floor or electric coils under the floor. This warmth is radiated up into the room, and replaces radiators.
  • U-value
    Indicates how well a part of the building (ie roof, window, door, wall) keeps the heat inside the building. It measures the heat flow through those components. The higher the figure, the higher the heat loss. It is measured in terms of how many watts (W) of thermal energy is transported through a component of 1 square meter (m2) at a temperature difference of 1 degree centigrade, ie W/m2.


  • Ventilation
    The controlled entry of fresh air into a building.

Our Partners

Working With