Eco Home Glossary

Air source heat pump

Air source heat pumps extract heat energy from the air outside and use it to heat your home and hot water. They work a bit like a refrigerator in reverse. They need some electricity to operate, but they output more energy than they use. They are very efficient and can operate when temperatures are as low as -15oC.

Air source heat pumps heat water to a lower temperature than traditional boilers, so are most effective when used with heating systems that provide comfortable heating at lower temperatures, for example underfloor heating, or radiators.

Suitable for well insulated homes

May be eligible for RHI payments.

See our case studies on Air source heat pumps and hear from the homeowners:

Air tightness membrane

An air tightness membrane is constructed from sheets of material, often self-adhesive, that are connected together to form a barrier protecting a building. The membrane is fixed to the warm side of the building’s insulation and:

  • prevents heat escaping
  • prevents draughts coming in
  • protects timber structures against condensation

It is important to minimise any breaks, or holes, in the membrane, so sheets are taped together and care has to be taken when attaching fixings to the membrane. A properly constructed air tightness membrane will increase the energy efficiency of homes to such an extent that very little heat energy is needed, even in winter. As no air can get in, Mechanical Ventilation Heat Recovery systems are usually installed in airtight buildings.

ECO – Energy Company Obligation

ECO is a government scheme to help reduce carbon emissions and tackle fuel poverty. Under this scheme customers with low incomes can apply to their energy supplier for help with energy efficiency measures, such as loft or wall insulation, or even boiler replacement. The aim is to reduce the cost of heating their homes. Medium and large energy companies (with over 150,000 customers) are obliged to provide a certain number of efficiency improvements according to their market share.

It’s a first come first served scheme, as once the energy companies have fulfilled their obligation within the current scheme, they may stop taking applications. The current Eco scheme (ECO 3) runs until 31st March 2022. The good news is that ECO 4 will run for four years from April 2022 with a planned expenditure of £1 billion per year.

6.5 million homes are eligible for help under ECO – You can find out whether you are eligible here . If you are eligible, you should contact your energy supplier for further information on services they provide.

Information on ECO from simple energy advice website

Electric boilers

As you’d expect an electric boiler uses electricity to heat water, so there is no need for a gas supply.

Electricity costs three times as much as gas, so per unit of energy they cost more to run. However, electric boilers are more efficient than gas boilers, so require less energy to produce the same amount of heat. They are also cheaper to install and maintain – there is less to go wrong. As they don’t burn gas, there are no carbon emissions and no danger of carbon monoxide poisoning. There is no need for a flue, so they don’t have to be installed on an outside wall. They are quieter and small than equivalent gas boilers.

They are suitable for small/medium, or well insulated, homes. They can be a good solution if you already have water based central heating system, e.g. radiators, or underfloor pipes and just want to replace your boiler without too much disruption.

Export Tariffs

Export tariffs are payments made when you sell surplus energy units back to your electricity supplier. The current rate is 5.24p per unit of electricity. There is usually a CAP on the amount of energy you can sell back to your supplier, but you can apply to have the level of the CAP increased.

Information on Export Tariffs from Octopus Energy.

Feed-in Tariffs (FIT)

Feed-in Tariffs are a government scheme designed to promote the uptake of renewable energy generation. They were first introduced in April 2010. The amount of money offered to homes with electricity generating features (FIT rate) was reduced over the years and the scheme was eventually closed to applications April 2019. Those who already have a FIT contract continue to receive FIT payments at their agreed rate. Payments are based on the amount of energy you generate, including the amount you use yourself within your home. They are calculated using meter readings and are paid quarterly.

Technology that was eligible for FIT payments included:

  • solar PV panels
  • wind turbines
  • micro compbined heat and power
  • hydro power
  • anaerobic digestion

See government information on Feed-in tariffs.

Feed-in Tariffs are paid additional to export tariffs.


Mechanical Ventilation with Heat Recovery (MVHR) is a whole house ventilation system that supplies air to and extracts air from a building with very little loss of heat. MVHR systems are intelligent and measure the moisture levels and temperature in a building and adjust accordingly. An MVHR system can cool buildings in summer, prevent dampness and condensation in winter and supply filtered, fresh air. An MVHR system uses very little energy and makes very little noise.

MVHRs are more effective in airtight buildings.

See our case studies on MVHR systems and hear from the homeowners: Newhaven installation

Renewable Heat Incentive (RHI)

The renewable Heat Incentive is a government scheme introduced in 2014 which aims to encourage businesses and home owners to install renewable heat technologies, by offering quarterly cash payments over seven years. Example of technologies include air to water heat pumps, ground to water heat pumps and solar thermal panels. Applications will close on 31 March 2022.

More information on RHI from the Energy Saving Trust.

Smart Meters

A smart meter is an electrical device which will record and display information such as consumption of electricity, voltage and current levels. A smart meter shows the consumer how much energy they are using and also sends information back to the suppler to monitor systems and simplify billing.

Smart Meters — Simple Energy Advice

Solar Photovoltaic Panels (Solar PV)

Solar PV panels capture energy from the sun and convert it into direct current (DC) electricity. Inverters are added to solar PV systems to convert the direct current into alternating current (AC) electricity.

The best position for solar panels is on an unshaded south facing roof. East and west facing roofs can also be used, but north facing roofs are not recommended. To generate half the electricity needed by a typical household you would need at least 20 square meters of suitable roof space.

The more panels you have, the more renewable electricity you can generate. If you generate more electricity than you need, you may be able to sell electricity back to the grid, but you must apply for this and there is usually a cap on how much you can sell back.

Solar Thermal Systems

Solar thermal systems use energy from the Sun to heat hot water. Solar panels fitted to the roof contain a mixture of water and anti-freeze. This mixture is heated by the Sun and the heat generated is transferred to your hot water system through a heat exchanger. In the UK, you are likely to need an additional boiler for times when sunshine is scarce, but a solar thermal system will reduce your heating bills and your carbon footprint. There are two main types of solar thermal systems, flat plate and evacuated tubes. Evacuated tubes take up less roof space and perform better than flat plates in low light conditions.

Solar thermal installations are generally cheaper than heat pumps to purchase and install, but are mainly used for hot water for use in the home, not for heating systems.

Solar thermal systems are currently eligible for RHI payments.

See our case study on a solar thermal installation in Pevensey and hear from the homeowners.