Technical Glossary

Our glossary aims to demystify some of our industry's technical and legislative terms.


The Energy Company Obligation (ECO)

The Energy Company Obligation replaced the previous supplier obligation schemes such as the Carbon Emissions Reduction Target (CERT) and the Community Energy Saving Programme (CESP), as well as the Warm Front scheme.

The ECO is a rebranding under which fuel suppliers will continue to improve the energy efficiency of buildings. ECO will supplement the Green Deal and will be focussed on "hard-to-treat" dwellings and on households in fuel poverty for which grants will be provided to pay for measures that fall outside the Golden Rule and therefore cannot be paid for by PAYS.

More details can be found on the DECC website.
*Correct at November 2014

Energy Savings Opportunity Scheme (ESOS)

The Energy Savings Opportunity Scheme (ESOS) was developed to comply with Article 8 (4) of the European Energy Efficiency Directive.

It requires UK companies with 250 employees or an annual turnover in excess of €50 million (£42.5 million) and an annual balance sheet total €43m (£36.5million) to undertake energy efficiency audits by 5 December 2015 and thereafter at least once every four years.

More details on the requirement can be found here: DECC
*Correct at November 2014

Enhanced Capital Allowance Energy Scheme (ECA scheme)

The Enhanced Capital Allowance Scheme (ECA scheme) enables a business to claim 100% first-year capital allowances on their spending on qualifying plant and machinery. The ECA scheme is open to all businesses that pay UK corporation or income tax, regardless of size, sector or location. There are three parts to the scheme covering:

• Energy-saving plant and machinery
• Low carbon dioxide emission cars and natural gas and hydrogen refuelling infrastructure
• Water conservation plant and machinery

The Energy Technology List (ETL) details the criteria for each type of technology, and lists those products in each category that meet them. The scheme provides 100% first-year capital allowances on investments in energy-saving equipment against taxable profits in the period of investment. Only spending on new and unused energy-saving equipment can qualify for ECAs but capital allowances are available for spending "on the provision of" plant and machinery. This can include certain costs arising as a direct result of the installation of qualifying plant and machinery, such as transport of the equipment to the site and some direct installation costs.

More details can be found on the Gov.UK website.
*Correct at November 2014

The Energy Technology List (ETL)

The Energy Technology List (ETL) details the criteria for each type of technology eligible for the Enhanced Capital Allowance Energy Scheme (ECA scheme) and lists those products in each category that meet them.

It is managed by the Carbon Trust, on behalf of the Government, and has two parts - The Energy Technology Criteria List (ETCL) and The Energy Technology Product List (ETPL). All the products listed on the ETPL must meet the energy-saving criteria published in the ETCL.

More details on eligible technologies can be found on the DECC website.
*Correct at November 2014

The Energy Technology Criteria List (ETCL)

The Energy Technology Criteria List (ETCL), alongside the ETPL, make up the Energy Technology List (ETL) of technologies that qualify for the Enhanced Capital Allowance Energy Scheme (ECA scheme).

This part of the list is reviewed annually to ensure that it reflects technological progress. It sets out the qualifying energy-saving criteria for each class of technology.

The Energy Technology Product List (ETPL)

The Energy Technology Product List (ETPL) is the second part, alongside the ETCL, of the Energy Technology List (ETL) that qualifies for the Enhanced Capital Allowance Energy Scheme (ECA scheme).

Updated at the start of each month, the ETPL lists the products and technologies that are eligible for an ECA.

The ETPL also contains details of the maximum claim values for qualifying products which comprise a component in a larger piece of plant and machinery, which does not itself qualify for ECAs.

Please note that the criteria and claim values listed on the Energy Technology List have now been updated to take effect from 7th August 2014.

More details on eligible technologies can be found on the DECC website.
*Correct at November 2014 

The Feed in Tariff (FiT)

The Feed in Tariff (FiT) is a scheme to promote the manufacture, supply installation and use of small-scale low-carbon electricity generating systems - Solar PV, small-scale wind power, domestic/small-scale combined heat and power (DCHP), small-scale hydropower and anaerobic digestion.

The electricity generated can be used on-site of the generation or exported to the national electricity grid. The electricity generated on-site attracts a payment dependent on the type of technology, the amount generated and the installation date. The exported surplus electricity attracts an additional payment.

These index-linked payments are currently tax-free to householders and will continue for 20-25 years. The FiT is funded by a levy on the bills paid by all electricity customers and it is expected that the tariffs paid to new entrants will reduce over time as the expected capital cost of installation falls, known as degression.

The rates payable and the installation dates these payments pertain to, vary depending on the technology and the date commissioned and whether the installation is new or an extension to an existing scheme.

For more details visit the DECC website

For the most up to date information on tariff rates please visit the OFGEM website.

Please note that this scheme is not available in Scotland. If you are based there then please click here for details on alternative resources
*Correct at November 2012

Golden Rule

Under the Green Deal, the expected fuel cost saving must be equal to or greater than the charges attached to the fuel bill.

The Green Deal

The Green Deal is a scheme to allow commercial organisations (Green Deal Providers) to offer energy efficiency improvements to homes at no capital cost to the householder or their landlord, and to recover their capital charges and profit from charges levied on the resident’s fuel bills.

This funding mechanism is known as Pay as you Save (PAYS). The charges remain with the building and remain will the dwelling.

Thus the Green Deal is not a conventional loan as the charge is only paid by those enjoying the benefits.

The Green Deal has 6 key features:

  1. The policy is subject to the Golden Rule
  2. The improvements must be identified in a Green Deal Plan, prepared by an accredited Green Deal Advisor who has carried out an assessment.
  3. The improvement measures identified must make use of approved/accredited materials and products and must be installed by an accredited installer.
  4. The Green Deal Provider must obtain the consent of all parties e.g. householder and landlord and give advice within the terms of the Consumer Credit Act, taking account of individual circumstances.
  5. The presence of a Green Deal charge must be disclosed to future occupants alongside the Energy Performance Certificate (EPC)
  6. Fuel suppliers must collect Green Deal charges and pass them on to the relevant Green Deal Providers within the existing regulatory safeguards for collecting fuel bill payments.

For up to date information please visit the DECC website.
*Correct at November 2012

Pay as you Save (PAYS)

A scheme such as the Green Deal, where commercial organisations offer energy efficiency improvements to homes at no capital cost to the householder (or their landlord), and where the provider recovers their capital charges and profit from charges levied on the resident’s fuel bills.

The Renewable Heat Incentive (RHI)

Similar to the Feed in Tariff (FiT), the Renewable Heat Incentive (RHI) provides regular capital payments for heat-generating renewable energy installations. Payments are dependent on the type of technology, the size of the scheme and the installation date and whether for consumer or business use.

The scheme provides guaranteed payments for 20 years. Qualifying heat technologies include, biomass, solar thermal, ground, water and air-source heat pumps, biogas, deep geothermal, energy from waste and bio-methane renewable heat installations. 

For more details please visit the DECC website.
*Correct at November 2012


Air Source Heat Pumps

Air source heat pumps use the outside air temperature as an energy source converting any temperature differentiation into useable heat to run heating or water heating systems.

An air source heat pump is usually installed on the outside of a building and can easily be retrofitted. GSHP systems typically operate at temperatures of around 55°C , hence their suitability for under floor and water heating , low temperature radiators or fan confection heaters.

They best suit buildings with adequate insulation and do not work with existing high temperature radiators. Systems may also be eligible for subsidy payments under the Renewable Heat Incentive.

Anaerobic Digestion

Anaerobic digestion is a collection of processes by which microorganisms break down biodegradable material in the absence of oxygenThe process is used for industrial or domestic purposes to manage waste and/or to produce fuels.

Anaerobic digestion is widely used as a source of renewableenergy. The process produces a biogas, consisting of methane, carbondioxide and traces of other ‘contaminant’ gases. This biogas can be used directly as fuel, in combined heat and power gas engines or upgraded to natural gas-quality biomethane. The nutrient-rich digestate also produced can be used as fertilizer.

With the re-use of waste as a resource and new technological approaches which have lowered capitalcosts, anaerobic digestion has in recent years received increased attention among governments in a number of countries, among these the United Kingdom, Germany and Denmark.

Biomass or Burning Boilers

Biomass or burning boilers use wood (or other biological matter) as a fuel which is considered carbon neutral, as the carbon dioxide produced during combustion is offset by the carbon dioxide absorbed during the plant's growth.

These boilers usually use logs, wood chip or pellets as fuel and are available in sizes ranging from 10kW upwards (small commercial is around 50kW). The fuel can either be manually fed or, added as an optional extra, supplied into the hopper via a vacuum pump system.

Biomass boilers are most suited to off mains gas grid locations or in urban areas where the fuel is readily available and the systems can operate on high temperature heating systems. Systems may also be eligible for subsidy payments under the Renewable Heat Incentive.

Combined Heat and Power Systems (CHP)

Combined heat and power systems are an extremely efficient way of producing useable heat and electricity simultaneously at the point of use from a single fuel.

Micro CHP operates just like a conventional boiler but with the added benefit of supplying some of your electricity needs. Depending on the size of the system, electricity/heat might also be eligible for the government Feed in Tariff or Renewable Heat Incentive payments.

In nearly all cases the system should be sized on the heat load of the unit, even though this will usually mean that some electricity will still need to be bought from an alternative source - usually the national grid.

Fuel Cells

fuel cell is a device that converts the chemical energy from a fuel into electricity through a chemical reaction with oxygen or another oxidizing agent.

Hydrogen produced from the steam methane reforming of natural gas is the most common fuel, but for greater efficiency hydrocarbons can be used directly such as natural gas and alcohols like methanol.

Fuel cells are different from batteries in that they require a continuous source of fuel and oxygen/air to sustain the chemical reaction whereas in a battery the chemicals present in the battery react with each other to generate an electromotive force(emf). Fuel cells can produce electricity continuously for as long as these inputs are supplied.

Greywater Recycling

Wastewater from all sources in a property (except the toilet) is known as greywater.

Most greywater recycling systems collect and treat water from wash basins, baths, and showers, but exclude the more heavily contaminated water from washing machines, dishwashers and kitchen sinks. The systems collect this water and re-use it for purposes that don’t need drinking quality water such as flushing toilets or watering gardens.

Grey water systems can be retrofitted and can make up to a 30% reduction in water consumption.

Ground Source Heat Pumps (GSHP)

Ground source heat pumps use the (solar) heat available in the ground as an energy source to provide heating and hot water.

A ground source system is best suited to a new build property off the mains gas grid, where is can be incorporated into an efficient under floor heating system. The associated pipe work can be placed in a bore hole, but is more normally run in a shallow trench over a broader expanse of land. GSHP systems typically operate at temperatures of around 55°C, hence their suitability for water and under floor heating, low temperature radiators or fan confection heaters.

Ground source heating may also be eligible for the Renewable Heat Incentive.

Rainwater Harvesting

Rainwater Harvesting is the collection of rain water that would otherwise have been lost and has the potential to save large amounts of mains water and, therefore, reduce the pressure on this increasingly valuable resource. Large surfaces such as roofs or driveways are ideal and can provide up to 100m3 (100,000 litres) of water per year from a medium sized area. This water can be used to flush toilets, water gardens, and even in certain circumstances to feed white goods that don't require drinking level water, such as washing machines.

Solar Photovoltaic (PV)

Solar Photovoltaic technology uses the power of the sun year round to generate electricity.

This electricity can be used on site or at times when it is not needed, and sold back to the national grid. Modules are mounted on a roof in a southerly direction and where there is no (or limited) shading. The electricity conversion process causes no waste and no emissions and is subject to subsidy under the current Feed in Tariff (FiT) scheme.

The solar PV package usually includes the panels, roof mountings, inverter, AC and DC isolators, generation meter and connections, etc.

Solar Thermal

Solar Thermal is an effective way of heating some of the water for a property - up to 65% in winter and up to 100% in summer.

What is required is a south facing orientation on which to place solar collectors. There are two types of solar collectors. Flat panels tend to be the most robust and have a solid flat front that many find more aesthetically pleasing. Evacuated tubes though are thought to be more efficient and weigh less. A solar thermal package is completed with solar storage cylinders, high temperature pipe insulation, mixing valves and roof lashings.

The heat produced might also be eligible under the Renewable Heat Incentive.

Variable Speed Drives

Variable-Speed drive (VSD) or Adjustable speed drive (ASD) describes equipment used to control the speed of machinery. Many industrial processes such as assembly lines must operate at different speeds for different products. Where process conditions demand adjustment of flow from a pump or fan, varying the speed of the drive may save energy compared with other techniques for flow control.

Where speeds may be selected from several different pre-set ranges, usually the drive is said to be 'adjustable speed'. If the output speed can be changed without steps over a range, the drive is usually referred to as 'variable speed'.

Voltage Optimisation

Voltage Optimisation technology, where appropriate, can help achieve energy savings of up to 19% by optimising a building's incoming electricity supply voltage.

In the UK the average incoming electricity supply is 242 volts, sometimes as high as 253 volts, whilst most modern electrical equipment is designed and optimised to operate at 220 volts.

A Voltage Optimisation system reduces the voltage down to 220 volts (some systems can maintain this output regardless of incoming voltage), thus bringing the following benefits:

  • Reduced site kWh consumption, energy costs and CO2 emissions by up to 19%
  • Provides additional protection to electrical equipment from potentially harmful transients.
  • Reduces your maintenance costs of electrical equipment, whilst extending the life of all electrical and electronic components.

The effectiveness of VO varies from building to building and depends upon various factors such as your incoming voltage supply, the type of equipment and how it is used. A full analysis of your building is carried out to establish an accurate energy savings projection.


With lighting accounting for an average of 20% - 40% of an organisation's total energy cost, latest generation LED (Light Emitting Diodes) lighting for both internal and external applications can reduce your lighting costs by up to 80%.

Significantly longer lifespans compared to traditional lighting products also dramatically reduce maintenance costs, often eclipsing the actual energy savings.


Heating, Ventilation and Air Conditioning refers to the collective technologies that provide environmental comfort in a building.

HVAC is critical in the design of medium to large commercial and industrial building to regulate temperature, humidity and fresh air within a building. Simple changes in settings can have significant impacts on energy consumption and, indeed, on how effectively the system operates.

Similarly, installing a more sophisticated system into an older building can provide attractive payback periods whilst improving the comfort levels for the occupants.

Technical Glossary

After conducting a very professional and thorough survey of our office, Eco-Nomics returned to present their findings to us in a straight talking and easy to understand format. We were impressed by the content of the report and they identified substantial potential savings of our current energy spend. We are now deciding on which measures to proceed with and look forward to an ongoing partnership with Eco-Nomics.