How Is EPC Calculated? A Comprehensive Guide

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Energy Performance Certificates (EPCs) are an essential aspect of buying, selling, or renting a property in many countries, including the UK. These certificates provide information about a property’s energy efficiency and estimated energy costs, helping potential buyers or tenants make informed decisions. 

But how is EPC calculated? In this comprehensive guide, we will delve into the methodology behind EPC calculations, the factors that influence a property’s rating, and the steps involved in obtaining an EPC for your property.

What is an Energy Performance Certificate (EPC)?

An Energy Performance Certificate (EPC) is a document that rates a property’s energy efficiency on a scale from A (most efficient) to G (least efficient). EPCs are required whenever a property is built, sold, or rented, and they are valid for ten years. In addition to the energy efficiency rating, EPCs also provide:

  • The property’s current and potential energy efficiency ratings
  • Estimated energy costs for heating, hot water, and lighting
  • Recommendations for improving the property’s energy efficiency

Overview of EPC Calculation Methodology

The EPC calculation methodology is based on the Standard Assessment Procedure (SAP) in the UK, which is the government-approved method for assessing a property’s energy performance. SAP uses a mathematical model that takes into account various factors such as the property’s size, construction materials, insulation, heating systems, and lighting to calculate its energy efficiency rating.

The overall EPC rating is expressed in terms of the property’s energy efficiency on a scale of 1-100, with higher numbers indicating better efficiency. This numerical rating is then translated into a letter grade ranging from A to G.

The SAP methodology is continually updated and refined to reflect advances in building technologies and improvements in our understanding of energy efficiency.

The Impact of Energy Efficiency on Your Home’s Value

Energy efficiency has become an increasingly important factor for homeowners, homebuyers, and real estate professionals alike. With growing awareness of environmental concerns, rising energy costs, and the desire for more sustainable living, energy efficiency can significantly impact a home’s value. 

Implementing energy-efficient measures not only reduces energy consumption and associated costs but also enhances the overall appeal and marketability of a property. Here are some ways in which energy efficiency can affect your home’s value:

Increased Market Demand: As more people prioritize energy efficiency when looking for a new home, properties with higher energy performance become more attractive to potential buyers. Energy-efficient homes typically spend less time on the market and may even command a premium price due to increased demand. With energy efficiency becoming a key selling point, having an energy-efficient home can give you a competitive edge in the real estate market.

Improved Comfort and Indoor Air Quality: Energy-efficient homes tend to be more comfortable and have better indoor air quality due to improved insulation, air sealing, and ventilation systems. These features help maintain consistent indoor temperatures, reduce drafts, and minimize moisture and mold issues. A comfortable living environment with good air quality is an attractive feature for potential buyers, contributing to a higher perceived value for your home.

Potential Financial Incentives: Many governments and utility companies offer financial incentives, such as tax credits, rebates, or low-interest loans, to encourage homeowners to invest in energy-efficient improvements. These incentives can help offset the initial costs of upgrading your home’s energy performance and increase its overall value by making it more affordable and attractive to potential buyers.

Enhanced Durability and Reduced Maintenance Costs: Energy-efficient homes often incorporate high-quality materials and construction techniques that result in enhanced durability and reduced maintenance costs. For example, energy-efficient windows and doors are typically better sealed and insulated, reducing the risk of air leaks and moisture damage. This can lead to lower repair and maintenance costs over time, which can be a selling point for potential buyers.

Lower Utility Bills: One of the most tangible benefits of energy efficiency is the reduction in utility bills. By investing in energy-efficient appliances, heating and cooling systems, insulation, and lighting, homeowners can significantly reduce their monthly energy costs. These savings can be particularly appealing to potential buyers who want to minimize their ongoing expenses. Moreover, lower utility bills make a home more affordable in the long run, which can positively impact its value.

Reduced Environmental Impact: With growing awareness of climate change and the need for sustainable living, many homebuyers are seeking properties that have a minimal impact on the environment. Energy-efficient homes produce fewer greenhouse gas emissions and consume fewer natural resources, making them more eco-friendly. By investing in energy efficiency, homeowners can demonstrate their commitment to sustainability, which can be an appealing factor for environmentally conscious buyers.

Higher Appraisal Values: As energy efficiency becomes a more significant factor in the real estate market, appraisers are increasingly considering energy-efficient features when determining a property’s value. A home with a high energy efficiency rating, such as one indicated by an Energy Performance Certificate (EPC), may receive a higher appraisal value, reflecting its potential for lower operating costs and increased demand from buyers.

Factors Influencing EPC Calculations

Several factors can influence a property’s EPC rating. Some of the key factors considered in EPC calculations include:

Building Fabric

The building fabric refers to the construction materials and insulation used in a property’s walls, roof, and floors. Properties with well-insulated walls, roofs, and floors will generally have better energy efficiency ratings than those with poor insulation.

Windows and Doors

The type, size, and glazing of windows and doors can significantly impact a property’s energy efficiency. Double or triple-glazed windows with low-emissivity coatings and well-sealed doors can help minimize heat loss and improve a property’s EPC rating.

Heating Systems

The efficiency and type of heating system installed in a property play a crucial role in determining its energy efficiency rating. High-efficiency boilers, heat pumps, and renewable energy sources such as solar panels can contribute to a higher EPC rating.


A property’s ventilation system can also impact its energy efficiency. Properly designed and installed ventilation systems can help maintain good indoor air quality while minimizing heat loss, contributing to a better EPC rating.


Energy-efficient lighting solutions, such as LED or compact fluorescent bulbs, can help reduce a property’s energy consumption and improve its EPC rating.

Property Size and Layout

The size and layout of a property can influence its energy efficiency rating. Smaller properties generally require less energy to heat and light, while open-plan layouts may allow for better heat distribution and natural light penetration.

Obtaining an EPC for Your Property

To obtain an EPC for your property, you will need to follow these steps:

Find an accredited energy assessor: You will need to hire a qualified energy assessor to carry out the EPC assessment. They should be accredited under an approved government scheme, ensuring that they have the necessary skills and knowledge to conduct the assessment accurately.

Schedule the assessment: Arrange a suitable date and time for the energy assessor to visit your property and perform the assessment. The assessor will need access to all areas of the property, including lofts, basements, and any outbuildings.

Prepare for the assessment: Before the assessment, you may want to gather any relevant documentation related to your property’s construction, insulation, heating systems, and other energy efficiency measures. This information can help the energy assessor make a more accurate assessment of your property’s energy performance.

The assessment: During the assessment, the energy assessor will inspect your property and collect data on its size, construction materials, insulation, heating systems, ventilation, lighting, and other factors that influence its energy efficiency. The assessor may also take photographs for their records.

Receive your EPC: Once the assessment is complete, the energy assessor will input the collected data into the SAP software to calculate your property’s energy efficiency rating. They will then issue your EPC, which will include the energy efficiency rating, estimated energy costs, and recommendations for improving the property’s energy performance.

Different Ways to Improve Your Home’s EPC Score

An Energy Performance Certificate (EPC) is a crucial document that rates a property’s energy efficiency on a scale from A (most efficient) to G (least efficient). A higher EPC score not only reflects a more environmentally friendly home but can also result in lower energy bills and increased property value. 

If you’re looking to improve your home’s EPC score, there are several steps you can take to enhance its energy efficiency. In this article, we will explore various ways to boost your home’s EPC score and create a more sustainable living environment.


One of the most effective ways to improve your home’s EPC score is by upgrading its insulation. Proper insulation helps to minimize heat loss through the walls, roof, and floors, reducing energy consumption and keeping your home warmer during colder months. Some insulation options to consider include:

  • Loft insulation: Adding or increasing the thickness of insulation in your loft can significantly reduce heat loss.
  • Cavity wall insulation: Filling the gaps between your home’s exterior walls with insulating material can help prevent heat from escaping.
  • Solid wall insulation: Insulating solid walls, both internally and externally, can improve your home’s energy efficiency and potentially save you hundreds of dollars on heating bills annually.

Windows and Doors

Energy-efficient windows and doors can play a significant role in reducing heat loss and improving your home’s EPC score. Consider the following upgrades:

  • Double or triple glazing: Installing double or triple-glazed windows can help to minimize heat transfer, keeping your home warmer in the winter and cooler in the summer.
  • Draught-proofing: Sealing gaps around windows and doors can prevent draughts and reduce heat loss. This can be done using weatherstripping, door sweeps, or brush seals.

Heating System

Upgrading your home’s heating system can have a substantial impact on its energy efficiency and EPC score. Some improvements to consider include:

  • Replacing an old boiler with a more efficient model: Modern condensing boilers are significantly more energy-efficient than older, non-condensing boilers and can help reduce heating costs.
  • Installing a smart thermostat: A smart thermostat allows you to control your heating remotely and create personalized schedules, ensuring that your home is heated efficiently and only when necessary.
  • Adding thermostatic radiator valves (TRVs): TRVs enable you to control the temperature of individual rooms, reducing energy waste by only heating the rooms you’re using.


Switching to energy-efficient lighting options, such as LED or compact fluorescent bulbs, can help to improve your home’s EPC score. These types of bulbs consume less energy and have a longer lifespan compared to traditional incandescent bulbs.

Renewable Energy Technologies

Incorporating renewable energy technologies into your home can significantly improve its EPC score by offsetting some or all of your property’s energy consumption. Some popular renewable energy options include:

  • Solar panels: Installing solar panels can help generate electricity for your home, reducing your reliance on the grid and lowering your energy bills.
  • Solar thermal systems: Solar thermal systems use sunlight to heat water, which can then be used for domestic hot water or heating purposes.
  • Air source or ground source heat pumps: These systems extract heat from the air or ground to provide heating and hot water for your home, offering a more energy-efficient alternative to traditional heating systems.

Other Factors That Can Affect Your Home’s EPC Rating

An Energy Performance Certificate (EPC) rating is a crucial factor for property owners to consider, as it provides valuable information about the energy efficiency and environmental impact of a home. 

While several well-known factors can influence a home’s EPC rating, such as insulation, heating systems, and windows, other lesser-known factors can also have an impact. In this article, we will explore some of these additional factors that can affect your home’s EPC rating, providing insights for property owners looking to improve their home’s energy performance.

Building Orientation

The orientation of your home can have a significant impact on its energy efficiency. South-facing homes tend to receive more sunlight throughout the day, which can help to reduce heating costs during the colder months. 

On the other hand, north-facing homes may require more energy to maintain comfortable indoor temperatures due to reduced sun exposure. When assessing a property for an EPC rating, the assessor may take the building’s orientation into account when determining its overall energy performance.


Proper ventilation is essential for maintaining good indoor air quality and preventing condensation issues, which can lead to dampness and mold growth. However, excessive or poorly controlled ventilation can also result in heat loss and increased energy consumption. 

When calculating an EPC rating, the energy assessor will evaluate the home’s ventilation system, including any mechanical ventilation systems or natural ventilation measures, such as trickle vents in windows.


The type of lighting used in a home can also affect its EPC rating. Energy-efficient lighting options, such as LED or compact fluorescent bulbs, consume less energy than traditional incandescent bulbs and can help to improve a home’s overall energy efficiency. 

The EPC assessment will take into account the proportion of low-energy lighting in the home and may recommend upgrading to more energy-efficient lighting options if necessary.


Draughts can significantly contribute to heat loss in a home, leading to increased energy consumption and reduced comfort for occupants. Effective draught-proofing measures, such as sealing gaps around doors, windows, and floorboards, can help to minimize heat loss and improve a home’s EPC rating. 

During the assessment, the energy assessor will check for signs of draughts and may recommend additional draught-proofing measures if required.

Renewable Energy Technologies

Incorporating renewable energy technologies, such as solar panels, wind turbines, or heat pumps, can help to reduce a home’s reliance on fossil fuels and improve its overall energy efficiency. 

Homes with renewable energy systems in place are likely to achieve higher EPC ratings, as these technologies can help to offset some or all of the property’s energy consumption. The EPC assessment will consider any renewable energy systems installed at the property when determining its overall energy performance.

Home Appliances

While the EPC assessment primarily focuses on the fabric and fixed services of a home, the energy efficiency of appliances can also have an indirect impact on a property’s EPC rating. 

Energy-efficient appliances, such as A-rated washing machines, refrigerators, and dishwashers, can help to reduce a home’s overall energy consumption and contribute to a higher EPC rating. 

Although appliances are not directly assessed during the EPC evaluation, homeowners looking to improve their property’s energy performance should consider upgrading to more energy-efficient appliances where possible.


Understanding how EPC is calculated can help property owners, buyers, and tenants make informed decisions about a property’s energy efficiency and potential for improvement. By implementing energy efficiency measures and working with a qualified energy assessor, you can improve your property’s EPC rating, potentially increasing its value and attractiveness in the market while reducing its environmental impact.

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Post written by: Sam Guest

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