How Your Heating System Affects the EPC Rating of a London Property
The energy performance certificate rating of a London property is heavily influenced by the type of heating system installed. Understanding how different heating systems are assessed under the Standard Assessment Procedure can help London landlords, sellers, and property investors make informed decisions about boiler upgrades and system improvements that will improve their EPC rating.
How the EPC Assessment Works for Heating Systems
An Energy Performance Certificate is produced using a methodology called the Standard Assessment Procedure (SAP), which is a Government-approved calculation method for assessing the energy efficiency of residential dwellings. The SAP calculation considers a range of factors including the thermal efficiency of the building fabric, the heating system type and efficiency, the hot water system, any renewable energy systems, and the lighting. The result is expressed as an energy efficiency rating from A to G, with A being the most efficient and G the least efficient, and a numerical score on a scale of 1 to 100.
The heating system has a very significant influence on the SAP calculation because it is both the primary source of energy consumption in most London properties and the component with the greatest variability in efficiency between different types and ages of installation. A modern A-rated condensing gas combination boiler with a seasonal efficiency of around 90 percent will produce a substantially better SAP score than an old G-rated non-condensing boiler with a seasonal efficiency of 65 percent in the same property. The SAP calculation also considers the heating system controls, with properties that have full programmer, room thermostat, and thermostatic radiator valve controls receiving a better score than properties with basic on/off controls.
The Impact of Boiler Age and Type on EPC Rating
In London, a very large proportion of the older Victorian and Edwardian housing stock is heated by gas central heating systems. The boiler in many older London properties may be a non-condensing floor-standing boiler or an older wall-mounted boiler that predates the introduction of mandatory condensing boiler requirements in 2005. These older boilers have SEDBUK (Seasonal Efficiency of Domestic Boilers in the UK) ratings that may be as low as 65 to 75 percent, compared to the 89 to 93 percent efficiency of a current A-rated condensing combination boiler.
Replacing an old non-condensing boiler with a new A-rated condensing combination boiler in a London property will typically improve the SAP score by 5 to 15 points, which may be sufficient to move the property up from a D to a C rating. This is particularly relevant in the context of the Minimum Energy Efficiency Standards (MEES) regulations, which currently require rental properties in England and Wales to have an EPC rating of E or above before they can be let, and which are expected to be tightened to require a C rating by 2030 for new tenancies. A London landlord whose property has a D or E rating may be able to achieve a C rating through a boiler replacement alone, without the need for more costly fabric improvement works such as insulation.
Heat Pumps and Their Effect on EPC Ratings in London
Air-source and ground-source heat pumps receive very favourable treatment in the SAP calculation because the methodology assigns them a very high efficiency rating based on their coefficient of performance, which is the ratio of heat energy delivered to electrical energy consumed. A well-specified air-source heat pump operating in a typical London climate will have a coefficient of performance of between 2.5 and 3.5, meaning it delivers 2.5 to 3.5 units of heat for every unit of electricity consumed. The SAP calculation, combined with the relatively low carbon factor assigned to electricity under the current SAP methodology, means that a heat pump can produce an EPC rating several bands higher than an equivalent gas boiler system in the same property.
However, heat pump installations in London properties require careful assessment. Many older London properties have radiators and pipework sized for the higher flow temperatures of conventional gas boiler systems, and a heat pump operating at the lower flow temperatures required for maximum efficiency may provide inadequate heat output through the existing radiators. A thorough heat loss calculation and system assessment by a qualified heating engineer is essential before committing to a heat pump installation in an older London property.
Hot Water Systems and EPC Ratings
The SAP calculation also considers the efficiency of the domestic hot water system. Properties with a combination boiler, which heats water on demand rather than storing it in a cylinder, are assessed differently from properties with a hot water cylinder. An uninsulated or poorly insulated hot water cylinder in an older London property represents a significant source of standing heat loss that adversely affects the SAP calculation. Replacing an old uninsulated cylinder with a modern factory-insulated cylinder, or upgrading from a stored hot water system to a combination boiler, can improve the EPC rating.
Prestige Engineers carry out boiler replacements, heating system upgrades, and heat pump installations across London, providing certificates of installation that domestic energy assessors require to update EPC ratings following system improvements. We can also advise on the most cost-effective heating system improvement to achieve a target EPC rating for a London property.