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Background Notes

Heat pumps or solar energy installed in over 300,000 BER-rated dwellings as of Q2 2025

Online ISSN: 2009-7441
CSO statistical release, , 11am

Introduction

A Building Energy Rating (BER) is an indication of the energy performance of a dwelling (represented in units of kWh/m2/year). Actual energy performance will depend on how the occupants operate the dwelling. A BER is based on the characteristics of major components of the dwelling including: wall, roof and floor dimensions; window and door sizes and orientations, as well as the construction type and insulation, ventilation and air tightness features; the system for heat supply (including renewable energy), distribution, and control; and the type of lighting. The BER certificate indicates the annual primary energy usage and carbon dioxide emissions associated with the provision of space heating, water heating, ventilation, lighting, and associated pumps and fans. The energy use is calculated on the basis of a notional family with a standard pattern of occupancy - hence data in this release giving average primary energy use or carbon dioxide emissions are not based on actual data. A BER only covers electricity used for heating, lighting and ventilation with associated pumps and fans. Electricity used for cooking, refrigeration, laundry and other appliance use are not included.

Since 1st January 2009, a BER certificate and advisory report is compulsory for all homes being sold or offered for rent. A BER is also required for new dwellings that apply for planning permission on or after 1st January 2007. A BER certificate is required to avail of the grants for energy-efficiency improvements to the home that are provided under the Better Energy Homes scheme.

Access to Microdata

Further information on the BER scheme (including links to a microdata research tool) is available on the Sustainable Energy Authority of Ireland website 

Revisions

The figures will be updated on a quarterly basis. While the changes to previous quarters will mainly relate to the most recent quarter, previous periods are also subject to revision mainly arising from some dwellings having another BER audit undertaken.

Coverage

There are three types of BER Certificates. A New Dwelling – Provisional BER is required for a dwelling that is not yet built but is offered for sale off the plans. A New Dwelling – Final BER is required for a newly-built dwelling before it is occupied. This certificate is based on data collected in a site survey carried out by a registered BER Assessor as well as drawings and specifications for the completed dwelling. An Existing Dwelling BER is required for any existing dwelling that is offered for sale or to let. An existing dwelling is one that has previously been sold or occupied. This is based on data collected in a site survey carried out by a registered BER Assessor. Both the New Dwelling – Final BER and the Existing Dwelling BER certificates are valid for 10 years from the date of issue. They become invalid if material changes are made to the dwelling during that period. This release is an analysis of Final and Existing BER certificates. To ensure that all tables are consistent with each other, records that contain missing data in any of the main classification variables used in this release have been excluded e.g. missing response for county. Records with only the main space heating fuel or main water heating fuel information missing have been included except in tables using those variables. 

National Representativeness

There were 1,285,235unique domestic BERs (one per dwelling) completed in the period 2009 to the end of June 2025. This compares with around 1.9 million occupied private households enumerated in the 2022 Census of Population. The 2022 Census of Population included questions on county of location of the dwelling, the period when the dwelling was built, and the type of dwelling. These questions can be used to weight the BER data to national level. Table 16 in the Background Notes presents an initial weighting of BERs up to national level of non-vacant households using the 2022 Census of Population. The weights were calculated by dividing the number of non-vacanthouseholds in the Census by the number of unique BER households. In cases where a household had more than one BER carried out only the most recent BER was used. A stratum was classified as a unique combination of County (52 categories - Dublin postal districts were distinguished), period of construction (nine categories) and dwelling type (four categories). The BER contains more disaggregated dwelling types, e.g. mid-terrace house, but these had to be aggregated to correspond to the Census classification. 

In mid-2015 the Census and BER files were allocated Eircodes. This makes it possible to match both files at household level as postcodes are unique at letter-box level. This will create an opportunity to calculate weights in a more precise manner. 

Table 16 BERs Weighted to National Level (2009-2025)
% of row  
Dwelling TypeEnergy Rating Total
AB1B2B3C1C2C3D1D2E1E2FG
Apartment18259101091095446182,997
Detached house114691010101095459705,047
Semi-detached house142381113121195444433,355
Terraced house1323810111010106556335,339
Total1335810111010954471,656,737

Non-domestic Buildings

Since 1st July 2008, a BER Certificate is required for all new non-residential buildings and from 1st January 2009 for all public service buildings and for existing non-residential buildings. The CSO publishes a quarterly release analysing this file.

Definitions

The BER rating scale is divided into categories from G (largest primary energy usage) to an A1 rating (lowest primary energy usage). The kilowatt-hour is the unit of energy used in Dwelling Energy Assessment Procedure (DEAP). The BER is measured in kWh per square metre of floor area of the dwelling per year (kWh/m2/year). The full range of categories is described in Table A. For the purposes of this release A1, A2, and A3 have been combined together because of the small number of Certificates in these categories. 

Table A: Building Energy Rating Categories
CategorykWh/m2/year
A1 ≤ 25
A2 > 25
A3 > 50
B1 > 75
B2 > 100
B3 > 125
C1 > 150
C2 > 175
C3 > 200
D1 > 225
D2 > 260
E1 > 300
E2 > 340
F > 380
G > 450

County is where the dwelling is located. 

Type of dwelling is selected from one of the following: Detached house; Semi-detached house; End of Terrace house; Mid-terrace house; Ground-floor apartment; Mid-floor apartment; Top-floor apartment; Basement apartment; and Maisonette. Some audit reports did not specify the type of house or apartment. 

Year of construction is when the dwelling was originally built. 

The fuel used by the Main Space Heating system. The main space heating system heats the largest proportion of the dwelling. This proportion is calculated using a count of the habitable rooms. It often provides hot water as well as space heating. 

The fuel used by the Main Water Heating system. This category has similar fuel response options to the Main Space Heating system. 

The Total Internal Floor Area of the dwelling is the total area of exposed and semi-exposed floors. It excludes any unheated areas that are thermally separated from the dwelling. The total energy usage is divided by the dwelling floor area to determine the Building Energy Rating.

A Heat Pump is defined as a renewable technology under Article 23 of the Renewable Energy Directive (2009/28/EC), where the heat source itself is renewable, and efficiency is at least higher than 100%. The specific threshold for efficiency under the directive varies by the efficiency of electricity production in a member state. In this release, heat pumps were identified by reference to the main space heating fuel being electricity and the efficiency being greater than 100%. 

The term Solar Energy here covers both solar thermal installations for water and space heating and solar photovoltaic installations for electricity generation. They are identified separately and combined, only counting dwellings with both thermal and photovoltaic installations once.

Table Notes

Table A spotlights a particular facet of the release data and can change from quarter to quarter. The release description will note which of the later tables the data derive from. 

Table 1 presents the number of Final and Existing BERs published by month since January 2009. A household that has had BERs conducted in different years is included in each year. This table gives an overview of the number of BER assessments being performed and will inform the user of changes since the previous quarterly analysis. 

Tables 2-14 only include the latest BER published for each dwelling from January 2009 to March 2025; hence the total number of BER certificates is lower than the total in Table 1.

Table 2 shows the general impact of the age of the dwelling on the BER profile. It can be linked with changes to the Building Regulations that require new homes to be more energy efficient. The number of BER certificates listing a given year of construction should not be taken to represent the number of new dwellings completed in that year.

Table 3 shows how the BER profile varies by type of dwelling. 

Tables 4-5 profile BERs by county and Dublin postal district. Table 4 is in county within province order. 

Tables 6-7 profile BERs by main space and water heating fuels respectively. Records with a missing response for main space heating fuel have been excluded from Tables 6 and 8-10. Similarly records with a missing response for main water heating fuel have been excluded from Table 7. 

Table 8 cross-classifies county by main space heating fuel. Mains gas is not generally available in some counties. Some counties use local heating fuels such as peat e.g. County Offaly. 

Tables 9-10 cross-classify main space heating fuel by period of construction and dwelling type. 

Table 11 cross-classifies dwelling type by period of construction.

Table 12 cross-classifies the average floor area by period of construction and the dwelling type. 

Tables 13 and 14 show the percentage share of renewable energy sources present. Table 13 shows the percentage of BERs with solar energy, and Table 14 shows the percentage of BERs with heat pumps by period of construction and dwelling type. Where heat pumps and solar energy have been funded by an SEAI grant, a post-works BER is needed before final payment. Installations that are not grant funded (e.g. solar energy on buildings built after 31 December 2020) may not have received a post-works BER and therefore could be underrepresented in these data. 

Table 15 is an analysis of properties that had BER audits carried out in more than one year, where the rating improved by at least one full letter from the earliest rating to the latest (i.e. B1 or below to any A rating, C1 or below to any B rating, D1 or below to any C rating, E1 or below to any D rating, F or G to any D rating, and G to F). The earliest and latest BER ratings are cross-classified to show trends in energy savings arising from insulation, retrofitting etc. 

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