Frequently Asked Questions (FAQ)



The information applies to current legislation, methodology and EPCs.



Q. The EPC says that the performance is ‘Poor’ or ‘Very Poor’, 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 ‘Poor’, or ‘Very Poor’, then this means that it results in higher than average fuel costs for the dwelling.

The "Current performance – Environmental" shows how much the element contributes to emissions of the greenhouse gas carbon dioxide (CO2). An element has an environmental performance of ‘Poor’ or ‘Very poor’ if it causes relatively more CO2 to be produced than average.

This relates to performance, 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.


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.


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 and weather. These factors vary appreciably between different households even if living in similar properties


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.


Q. What does the summary of this home’s energy performance related features show?
On page 3 of the Energy Performance Certificate there is a summary of the dwelling’s 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. The assessment is against the following scale: Very poor, Poor, Average, Good, Very good. The performance is assessed by the software on the basis of age of property, construction type and features.
This relates to performance, not appearance. It does not take into account the physical condition or quality of the element.



Q. I have added insulation to my house, but the SAP rating is low and the insulation is not shown on the EPC, why is this?
The RdSAP survey is a non-invasive survey and for insulation to be included in the assessment there must be evidence, either visual or documentary evidence of specific works relating to the property being assessed. This means that if insulation has been added but there is no access for the energy assessor to inspect it nor documentary evidence, it cannot be included. In these cases the level of insulation is assumed from the age of the relevant part of the dwelling.
This applies to roof insulation, floor insulation and wall insulation.



Q. Surely my house is better than indicated in the report?
The EPC gives information on the current and potential energy performance of the property. It does not cover its current condition or decorative state.


Q. I have a very modern electric heating system in my home. However, on page 3 of my EPC it declares my ‘Main Heating’ to have an ‘energy efficiency’ rating of ‘Very Poor’– why is this?
The current performance of the ‘main heating’ in the Energy Efficiency column in the table on page 3 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. Currently, mains gas 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 in the table on page 3 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.




Q. What is an RdSAP energy assessment?
An accredited Energy Assessor visits the property to collect only the data required for assessing energy features, and creates the certificate based upon 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.




Q. My EPC lists a number of recommendations that seem inappropriate as they recommend changing items that I have recently updated, renovated or had replaced.
An EPC is purely concerned with identifying the current and potential energy performance of a property. The EPC assessment does not look at the age or physical condition of any of the elements assessed but rather the energy efficiency.


Q. My recent EPC makes the recommendation of changing my current boiler to a new “band A” boiler, but I have only recently had my boiler changed, why is this?
The EPC is looking at 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 does not take into account 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.



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. It might be that only enhanced, more costly improvements are identified for your property; if that is the case, these are indicated towards the end of the report under "Further measures".


Q. I have what I believe to be a highly efficient LPG/oil heating system in my property. However on page 3 of my EPC it declares my ‘Main Heating’ to have an ‘energy efficiency’ of ‘Poor/Average’ – why is this?
The current performance of the ‘main heating’ in the ‘energy efficiency’ column in the table on page 3 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 (Liquified 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 3 of EPC informs the consumer about their 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 indicate “Good” or “Very Good”, whereas an oil boiler of the same efficiency will indicate “Average” and an LPG boiler of the same efficiency will indicate “Poor”.




Q. I have a programmer and a thermostat on my boiler but on page 3 of the EPC, it declares my ‘Main Heating Controls’ to have an ‘energy efficiency’ rating of “Poor” or “Very Poor” – how can this be?
Current building regulations standards are usually met by fitting a programmer to the boiler, by providing a room thermostat and by fitting thermostatic radiator valves (TRVs) on all but one radiator. A home with all three of these would have a better rating in the table on page 3 of the EPC than "Poor" or "Very poor"; which apply to a property that does not have all three of these components.

A property with a programmer allows an occupant to control the times the heating is in operation.

A thermostat sited on the boiler itself only controls the flow temperature of the water leaving the boiler and is a less efficient way of controlling room temperature than a room thermostat. A room thermostat located on an internal wall within the property allows occupants to set the temperature within the property, and will produce better comfort levels for occupants than a boiler thermostat.

TRVs allow occupants to set different temperatures in different rooms, thus further improving comfort levels within the dwelling.

The addition of both a room thermostat and TRVs will improve the current performance rating of the ‘Main heating controls’ on page 3 of the EPC. There are also other more sophisticated forms of heating controls, such as zone control and a boiler energy manager.




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.


Q. This has not answered my question. What can I do now?
In the first instance contact the energy assessor, whose details are on page 2 of the report. If that does not resolve the issue contact the accreditation scheme whose details are also on page 2 of the report.


The information applies to current legislation, methodology and EPCs.