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 second 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. My house has a low rating but there are no improvement options – why not?
8 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?
9 Q. What is “primary energy”?
10 Q. What does the summary of this home’s energy performance related features show?
11 Q. Why do some elements in the “Summary of this home’s energy performance related features” table not have a star rating?
12 Q. An ‘indicative’ cost is shown for the recommendations on page 5 of my EPC; what does this mean?
13 Q. The EPC says that the performance rating is only 1 or 2 stars – what does this mean?
14 Q. I have what I believe to be a highly efficient LPG/oil heating system in my property. However on page 4 of my EPC my ‘Main Heating’ has an ‘energy efficiency’ of only 2 or 3 stars – why is this?
15 Q. I have a very modern electric heating system in my home. However, on page 4 of my EPC ‘Main Heating’ has an ‘energy efficiency’ rating of only 1 star – why is this?
16 Q. A 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?
17 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?
18 Q. My EPC lists a number of recommendations that seem inappropriate as they suggest changing items that I have recently updated, renovated or replaced
19 Q. This has 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 the house 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 be 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 deleterious 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.epbniregister.com, click the link to retrieve an Energy Performance Certificate 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 the 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 second 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, they do not account for all energy use 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. My house has a low rating but there are no improvement options – why not?

The potential ratings are based on the adoption of cost-effective improvements only. It might be that enhanced, more costly improvements could be made; if so, these are indicated towards the end of the report under Further measures.

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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 nor 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. What is “primary energy”?

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?

On page 4 of the Energy Performance Certificate is a summary of the dwellings energy performance. Each element (walls, roofs, heating system, etc.) of the dwelling has been given an assessment of the current energy efficiency and environmental performance of between one and five stars. The performance 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 the recommendations on page 5 of 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 EPC says that the performance rating is only 1 or 2 stars – what does this mean?

The "Current performance - Energy Efficiency" shows how much 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. The "Current performance - Environmental" show how much the element contributes to emissions of the greenhouse gas carbon dioxide (CO2). An element has an environmental performance of 1 or 2 stars if it causes relatively more CO2 to be produced than average. This relates to energy efficiency and environmental impact, 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 and contribute to CO2 emissions.

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Q. I have what I believe to be a highly efficient LPG/oil heating system in my property. However on page 4 of my EPC my ‘Main Heating’ has an ‘energy efficiency’ of only 2 or 3 stars – why is this?

The current performance of the main heating in the "Energy Efficiency" column in the table on page 4 of the EPC is related to the cost of running the heating system. This takes into account the price of the fuel used and the efficiency of the heating appliances. Mains gas is a relatively cheap fuel; oil is significantly more expensive and LPG (Liquid Petroleum Gas) is even more expensive. Therefore, if a home has a mains gas boiler it will cost less to run than an oil or LPG boiler of the same efficiency. The "Energy Efficiency" column in the table on page 4 of EPC 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 mains 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, on page 4 of my EPC ‘Main Heating’ has an ‘energy efficiency’ rating of only 1 star – why is this?

The current performance of the "main heating" in the "Energy Efficiency" column in the table on page 4 of the EPC is related to the cost of running the heating system. This takes into account the price of the fuel used and the efficiency of the heating system. Electricity is significantly more expensive than mains gas. Currently, mains gas is one of the cheapest forms of fuel. Current fuel prices are based on the latest price information, and these will change over time. 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 in the table on page 4 of the EPC therefore informs the consumer about their heating system purely from a cost perspective. The descriptions in the table will therefore change 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. A 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. This has not answered my question. What can I do now?

In the first instance contact the assessor, whose details are on the first page of the report. If that does not resolve the issue contact the accreditation scheme whose details are also on the front page of the report.

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The information applies to current legislation, methodology and EPCs.