Areas of Significant Energy Consumption (AoSEC)
Under ESOS, the areas of significant energy consumption (AoSEC) are the assets and activities, typically buildings, transport and industrial processes, that together account for at least 95% of an organisation's total energy use and must therefore be covered by energy audits.
What is Areas of Significant Energy Consumption (AoSEC)?
ESOS does not require an organisation to audit every kilowatt-hour it uses. Instead, participants identify their areas of significant energy consumption, the sites, fleets and processes that make up the bulk of energy use, and concentrate auditing effort there. The areas chosen must cover at least 95% of total energy consumption; the remaining share, up to 5%, can be treated as de minimis and excluded. This threshold was raised from 90% to 95% by the 2023 ESOS amendment, so it applies from Phase 3 onwards.
Defining AoSEC is one of the first analytical steps in an ESOS assessment, because it determines the scope and cost of the audit work that follows. An organisation begins by measuring total energy across buildings, transport, and processes over its reference period, then ranks consumption to find the assets that collectively reach the 95% threshold.
Getting AoSEC right matters for compliance and for value. Too narrow a definition risks falling below the 95% coverage requirement; too broad a definition wastes audit effort on immaterial sites. A clear, data-led AoSEC selection also makes the resulting energy-saving opportunities more representative of where the organisation actually spends money on energy.
Practical Examples
A retailer with 120 stores finds that its 40 largest stores and its distribution centre account for 96% of energy use, so it defines these as its AoSEC and audits them, excluding the smallest sites as de minimis.
A manufacturer identifies that compressed air, process heating, and its main factory building make up the majority of energy, designating them as areas of significant energy consumption for detailed audit.
A logistics company includes its HGV fleet within its AoSEC because transport fuel represents over half of total energy consumption.
How Climatise Helps
Climatise maps total energy across sites, fuels, and transport, then ranks consumption so you can quickly identify the areas of significant energy consumption that reach the 95% ESOS threshold, with the underlying data retained as evidence.
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