Frequently Asked Questions (FAQ)

The information applies to current legislation, methodology and EPCs.


1. Q. What is an energy assessment?
2. Q. How do I check that an EPC is valid?
3. Q. Why are the potential heating costs greater than the current heating costs when the EPC recommends low energy lighting is installed?
4. Q. The costs shown on the EPC are higher than my actual energy bills for the year, why is this?
5. Q. Why are the energy costs shown on the front page of my EPC lower than my energy bills?
6. Q. My property is maintained to a high standard; surely the rating should be higher than shown in the report?
7. Q. I have added insulation to my house, but the rating is low and the insulation is not shown on the EPC, why is this?
8. Q. Why is a home’s heat demand not the same as the “primary energy”
9. Q. What does the summary of this home’s energy performance related features show?
10. Q. Why do some elements in the “Summary of this home’s energy performance related features” table not have a star rating?
11. Q. An ‘indicative’ cost is shown for recommendations on my EPC; what does this mean?
12. Q. The summary section of the EPC shows a performance rating of only 1 or 2 stars for one or more elements – what does this mean?
13. Q. I have what I believe to be a highly efficient LPG/oil heating system in my property. However in the summary section of my EPC my ‘Main Heating’ has an ‘energy efficiency’ of only 2 or 3 stars – why is this?
14. Q. I have a very modern electric heating system in my home. However, in the summary section of my EPC ‘Main Heating’ has an energy efficiency rating of only 1 star – why is this?
15. Q. My property is heated by conventional electric heaters and the EPC recommends the installation of storage heaters. The resultant change makes the Environmental Impact Rating worse rather than better – why is this?
16. Q. My recent EPC makes the recommendation of changing my current boiler to a new condensing boiler, but I have only recently had my boiler changed – why is this?
17. Q. My EPC lists a number of recommendations that seem inappropriate as they suggest changing items that I have recently updated, renovated or replaced
18. Q. These FAQs have not answered my question. What can I do now?


Q. What is an energy assessment?

An accredited Energy Assessor visits the property to collect only the data required for assessing energy features, and generates an Energy Performance Certificate (EPC) using government-approved software. The assessment is based on the construction and type of dwelling and relevant fittings (heating systems, insulation or double glazing, for example). It is not a structural or building survey, condition report or property valuation. An EPC should not be read as a comment on the overall condition of the property nor will it comment on the presence or otherwise of asbestos, high alumina cement concrete, additives including calcium chloride, or any building defects or hazardous materials. It will also not cover items or problems in the property which would be picked up in a building survey, which may be costly to rectify, as these are outside the scope of the data collected.

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Q. How do I check that an EPC is valid?

Go to www.epcregister.com and click the link to access the Domestic EPC Registers. Click on ‘Report Retrieval’ and follow the instructions on the screen.

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Q. Why are the potential heating costs greater than the current heating costs when the EPC recommends low energy lighting is installed?

This occurs when low energy lights are recommended and there is no recommendation for improvements to the heating system (usually because an efficient system is already installed). Standard light bulbs generate more heat than low energy light bulbs; by replacing standard bulbs with low energy bulbs the heat generated by the lighting is reduced and the heating system has to make up the difference. The reduction in the lighting cost is appreciably greater than the increase in the heating cost, so there is a net reduction in energy costs for the property.

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Q. The costs shown on the EPC are higher than my actual energy bills for the year, why is this?

EPCs use standardised assumptions so as to make properties directly comparable while still reflecting the features of individual properties. The EPC costs are based on a number of assumptions: a standardised heating pattern, number of occupants, hot water usage, etc. These factors vary appreciably between different households even if living in similar properties.

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Q. Why are the energy costs shown on the front page of my EPC lower than my energy bills?

Standard occupancy is used to ensure the EPCs can be compared by prospective buyers or tenants with other homes. The EPC costs account for energy used for heating, lighting and hot water, but do not include for other energy uses in a property, for example cooking or electrical appliances. An EPC is calculated based on standard occupancy rather than how an individual uses the property and appliance use can vary significantly between users.

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Q. My property is maintained to a high standard; surely the rating should be higher than shown in the report?

The EPC gives information on the current and potential energy performance of the property. It does not reflect the current condition of fabric or fittings, nor decorative state.

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Q. I have added insulation to my house, but the rating is low and the insulation is not shown on the EPC, why is this?

The energy assessment is non-invasive. For insulation to be included in the assessment there must be evidence, either visual or documentary, of specific works relating to the property being assessed. If insulation has been added but there is no access for the energy assessor to observe it or relevant documentary evidence, it cannot be included. In these cases the level of insulation is assumed based on the age of the relevant part of the dwelling. This applies to roof insulation, floor insulation and wall insulation.

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Q. Why is a home’s heat demand not the same as the “primary energy”

A home’s heat demand is the amount of energy the dwelling would require to heat it to standard occupancy levels and to provide hot water, without consideration of the efficiency of the heating system. Primary energy is a measure of the energy required for lighting, heating and hot water, taking account of the efficiency of the heating system (and the power station efficiency in the case of electricity) and the energy expended in extracting the fuel from its source and in conveying it to the dwelling.

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Q. What does the summary of this home’s energy performance related features show?

This is a summary of the dwelling’s energy performance. Each element (walls, roofs, heating system, etc.) of the dwelling has been rated between one and five stars based on energy efficiency (one star being least efficient and five stars most efficient). The rating is assessed by the software on the basis of age of property, construction type and features. This relates to energy efficiency, not appearance. It does not take into account the physical condition or quality of the element.

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Q. Why do some elements in the “Summary of this home’s energy performance related features” table not have a star rating?

A star rating for secondary heating is not shown in the “summary of this home’s energy performance related features” because no recommendations are made for improvement of secondary heating. A star rating for floor insulation is not shown because the thermal performance of the floor depends not only on the construction and insulation levels but also on the size and shape of the floor, so that comparison between different properties is not meaningful.

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Q. An ‘indicative’ cost is shown for recommendations on my EPC; what does this mean?

The indicative cost of recommendations are those that apply to a typical property. They may differ for very small or very large properties or ones with special features. The cost data are compiled by the Energy Saving Trust from various sources including EST's Housing Model and Low Carbon Building Programme Analysis.

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Q. The summary section of the EPC shows a performance rating of only 1 or 2 stars for one or more elements – what does this mean?

Energy Efficiency shows the extent to which the element contributes to the fuel costs of the dwelling. If an element has an energy efficiency performance of 1 or 2 stars this means that it results in higher than average fuel costs for the dwelling. This relates to energy efficiency, not appearance. It does not take into account the physical condition or quality of the element. It is an indication of how much more (or how much less) the home will cost to run.

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Q. I have what I believe to be a highly efficient LPG/oil heating system in my property. However in the summary section of my EPC my ‘Main Heating’ has an ‘energy efficiency’ of only 2 or 3 stars – why is this?

The ‘Energy Efficiency’ column in the summary section of the EPC is related to the cost of running the heating system. This takes into account a three year rolling average price of the fuel used and the efficiency of the heating appliances. The Energy Efficiency column informs the consumer about the heating system purely from a cost perspective. The descriptions in the column therefore change depending on the fuel used and the efficiency of the heating system. For example, a gas condensing boiler will have 4 or 5 stars, whereas an oil boiler of the same efficiency will have 3 and an LPG boiler of the same efficiency will have 2.

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Q. I have a very modern electric heating system in my home. However, in the summary section of my EPC ‘Main Heating’ has an energy efficiency rating of only 1 star – why is this?

The Energy Efficiency column in the summary section of the EPC is related to the cost of running the heating system. This takes into account the price of the fuel used (per kWh) and the efficiency of the heating system. Electricity is significantly more expensive than mains gas, which is one of the cheapest forms of fuel. For example, if a home has a mains gas boiler it will cost less to run than an electric boiler or electric storage heaters. The Energy Efficiency column informs the consumer about the heating system purely from a cost perspective. The ratings in the table will vary depending on the fuel used and the efficiency of the heating system. Even though an electric heating system may be 100% efficient at the point of use, turning all the electricity used into useful heat, it will still be more expensive for a home owner to run than a 65% efficient mains gas boiler. A gas boiler will have heat losses associated in converting the burning fuel into useful heat for the property, but these losses are outweighed by the lower cost of mains gas.

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Q. My property is heated by conventional electric heaters and the EPC recommends the installation of storage heaters. The resultant change makes the Environmental Impact Rating worse rather than better – why is this?

Storage heaters are recommended as they are cheaper to run, making use of low-rate night-time electricity. However the total amount of electricity used by a storage heater system is greater than that used by conventional panel heaters. Therefore the resultant Energy Efficiency Rating is improved as running costs are reduced but the Environmental Impact Rating is made slightly worse as the total amount of energy used increases.

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Q. My recent EPC makes the recommendation of changing my current boiler to a new condensing boiler, but I have only recently had my boiler changed – why is this?

The EPC provides an indication of the potential energy performance of the property and in this case has identified that the current boiler is not the most efficient boiler available. The recommendation to improve the boiler to a more energy efficient boiler is made purely on the energy efficiency rating of the boiler and is not a reflection of the age or condition of the currently installed boiler. This recommendation identifies that there are more efficient boilers available and that a homeowner should consider this when they next have to replace the boiler.

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Q. My EPC lists a number of recommendations that seem inappropriate as they suggest changing items that I have recently updated, renovated or replaced

The EPC identifies the current and potential energy performance of the property but does not take into account the age or physical condition of any of the elements assessed.

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Q. These FAQs have not answered my question. What can I do now?

In the first instance contact the energy assessor, whose details can be found in the ‘About this document’ section of the EPC. If the assessor is unable to resolve the issue to your satisfaction, contact their accreditation scheme whose details are given in the same section.

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The information applies to current legislation, methodology and EPCs.