The framework for an effective energy management system (EnMS) to improve energy-related performance has been provided by the ISO 50001 standard since 2011. In order to improve its applicability and align it with the common ISO basic structure, the standard was thoroughly revised and republished in 2018. Read the following article to find out which changes and improvements the current version of the standard brings.

Energy assessment - what does ISO 50001 SAY?

Energy assessment is critical to effective energy management. It is referred to by the revised standard as a "tactical" part of the energy planning process (Figure A.2 in the Appendix). Clause 3.5.5 defines it as "analysis of energy efficiency, energy use, and energy consumption, based on data and other information, leading to the identification of SEUs and opportunities for improving energy-related performance."

What are the results used for?

The results of the energy assessment are used to consider risks and opportunities (Section 6.1), feed into the energy planning process (Clause 6.2), and provide information for the context of the organization (Clause 4.1). They also provide critical input for the formulation and prioritization of goals (6.2.2).

It is important to take a closer look at the areas with significant energy use and to map energy performance indicators and relevant variables for these areas. This must be documented as part of the energy assessment and continuously improved through the PDCA cycle.

Consideration of the "SEU" in energy management

The English abbreviation "SEU" (significant energy use) means "significant energy use". In the company, this refers to those areas in which significant energy use takes place, e.g. plants, systems, processes or facilities - or in other words: areas with a significant share of total energy consumption or a clear lever for improving energy-related performance.

The requirement to consider significant energy use has become more specific with the revised ISO 50001. Thus, the significant areas identified under the previous procedure must now be considered in detail. For each area, the following must be determined:

  • Persons with energy relevance
  • Its energy-related performance (as a key figure)
  • Relevant variables

Energy assessment - the new process

According to the old standard (ISO 50001:2011), the first step in energy assessment was to estimate future energy use and consumption. Only then did opportunities for improvement have to be identified and prioritized. According to the requirements of the new standard (ISO 50001:2018), it makes sense to do this the other way around, as can be seen from subsections d) and e) of Clause 6.3 "Energy assessment." The reason is obvious: It actually makes sense to estimate future energy use and energy consumption only when the identified opportunities for improvement can be taken into account. This should make energy management even more efficient in the future.

Influencing factors - relevant variables and static factors

ISO 50001 distinguishes between two types of influencing factors:

1. Relevant variables

Quantifiable (measurable) factors with a significant influence on energy-related performance and the property of being able to change or be variable, e.g. production quantities, weather or indoor temperatures.

2. Static factors

These have a significant influence on energy-related performance, but are comparatively unchangeable and are considered to have already been determined, e.g., facility sizes, portfolio, equipment, or buildings (Clauses 3.4.8 / 3.4.9).

The associated requirements in brief:

  • For each SEU, the relevant variables as well as EnPI must be determined (chap.6.3).
  • Relevant variables and static factors must be considered in the formation of EnPI and the energetic baseline (EnB) (6.4 / 6.5).
  • EnPI must be checked for plausibility and dependence (6.4).
  • Appropriate data must be collected for relevant variables and static factors.

What should be considered regarding the "SEU"?

Differentiation between variable influences and static factors is important. The variable influences must be given special consideration in the case of energy-intensive sectors and their energy performance indicators (Clause 6.3 ff). The static factors can lead to an adjustment of the energy baseline in case of a change.

For example, if a new building is constructed, a completely new product is added to the portfolio (e.g., aluminum components), or a production line is retooled to the latest state of the art, this change in a static factor may lead to an adjustment of the EnB for the corresponding area. It is still permissible to create multiple output bases within a single company.

Meaningful key figures for the energy management system

Important tasks in practice are especially the consideration of relevant variables in the formation of key figures and their verification. Variables with a significant influence must be recorded and their data processed further. In terms of data collection, this means that other operating data must be used in the energy management system in order to obtain meaningful results.

For example, the EnPI "energy consumption in kWh related to operating hours" might be meaningful for one company, but for another it only provides an effective statement of energy-related performance when the product mix and order situation are taken into account.

Improvement in energy-related performance

Evidence of improvement must be provided in accordance with ISO 50003 certification criteria. Following ISO 50006, a selection of options is available here, e.g.

  • Reduction of total consumption under constant conditions
  • Improvement in energy efficiency (represented by a verified key figure) in relation to the base year: the specific consumption of an SEU decreases in relation to the base year
  • Progress in achieving an energy target
  • Improvement verifiable in an implemented individual measure (representation e.g. via project indicator), trend value determinations via organizational measures, e.g. introduction of coordinated maintenance or leakage inspections.

Evidence of continuous improvement

Special attention is paid to retrospective observation. If, for example, an audit takes place in 2020, the company must be able to demonstrate an improvement by then already for the year 2019. The requirement to be able to demonstrate continuous improvement is found in Clause 10.2 of the current version of the standard. Continuous improvement is defined as a "recurring activity to improve performance" (Clause 3.4.16).

Annex A.4 explains that the evidence of continuous improvement does not have to include all EnPI values, so it is sufficient if there is an improvement with regard to the entire scope. According to Annex A.10, the new standard states that improvements should be made periodically. The frequency, scope and timeframe of the measures are based on the context of the company, economic factors and other circumstances.

Further cross-reference to ISO 50003:2021

According to ISO 50003, improvement must be demonstrated at each initial certification and thereafter at each recertification. In doing so, the improvement must be assessed by comparing the EnPI with the associated EnB. During the surveillance audits, on the other hand, the focus of the verification is on the implementation of measures for improvement. The reduction of the total consumption is only acceptable as evidence if the framework conditions have not changed or have changed only insignificantly, i.e. no relevant variables are present.

As stated in ISO 50001:2018, A.4, demonstrating continuous improvement in energy-related performance across the scope and within the boundary(s) of the EnMS does not mean that all EnPI values improve. Some EnPI values improve while others do not; however, over the entire scope of the EnMS, the organization demonstrates improvement in energy-related performance. Thus, in addition to EnPIs for the SEUs, metrics are required for the organization as a whole, because the addressee of all ISO 50001:2018 requirements is "the organization," which must achieve and record improvement in its system and performance. In this context, the organization-related metrics must provide a general trend development.

For organizations with multiple sites, each site does not contribute equally to improving energy-related performance. Similar to a single site, a multi-site organization may define energy-related performance improvement at different levels. These could include the entire organization, individual sites, the system, processes, or equipment. As mentioned earlier, the organization as a whole must demonstrate its performance improvement.

What does improvement mean specifically?

As mentioned earlier, under continuous improvement, improvements are expected to occur periodically. Here, "continuous" means occurring over a period of time, but may include intervals of interruption (as opposed to "continuous," which describes occurrence without interruption).

Improvement in energy-related performance can be demonstrated, for example, as a reduction in normalized energy consumption or by progress toward energy goals.

For example, for a commercial building in a region where temperature does not vary significantly, it would be possible to demonstrate decreasing total energy consumption over time under otherwise similar conditions.

It would also be conceivable that a company's total energy consumption increases, but the specified EnPI improves. This is a simple relationship where there is a relevant variable and no base load. This would be the case, for example, if a company purchases additional equipment, resulting in an overall increase in consumption, but that equipment is significantly more energy efficient than the existing equipment.

Another example relates to equipment that shows a reduction in energy-related performance as it ages, e.g., due to wear and tear.

Delaying or reducing performance degradation as a result of appropriate management of operations and maintenance can demonstrate improved energy-related performance as determined by the organization's EnPIs.

Energy management and its significance to an organization - a case study

Our sample company is a medium-sized industrial enterprise in the steel sector. It supplies components for engine production, which are manufactured in its own foundry. 200 employees work there in the production process (foundry 35, parts machining 165 employees). The output: approx. 1000 t of molten iron per month in the foundry area as well as a number of components manufactured from it, such as gear wheels, flywheels, etc. in the parts machining area in multi-shift operation.

The company first determined the total energy consumption with all energy types (electricity approx. 28 GWh p.a., gas 2.6 GWh p.a., district heating 2 GWh p.a.). When considering how much energy is used where in the company, it was possible to determine that the electrically operated smelter with induction furnaces accounts for just under 37% of the total amount of energy, but predominantly electricity (approx. 10 GWh p.a.).

Thus, on the basis of the company's own criteria (here from 10 % share of total consumption), the smelter was identified as a significant area (SEU). The following points must now be defined for the "smelter" area:

  • Personnel with an influence on the energy consumption and efficiency of the smelter (preferably decision-makers)
  • An energy performance indicator EnPI, e.g. kWh electricity per ton of iron melted
  • Relevant variables

The company thus looks at the melting area and jointly considers which changing influencing factors could affect the melting performance, e.g. the product mix driven, i.e. steel grades effectively produced.


The use of an energy management system (EnMS) often achieves considerable and almost costless savings potential through simple organizational measures. The current version of ISO 50001 aims to help companies make the best use of their energy-consuming assets and promote more efficient energy use throughout the process chain. The new, common High Level Structure (HLS) creates compatibility with other management system standards such as ISO 9001, ISO 14001 or ISO 45001, which is a noticeable advantage when introducing or converting and implementing an integrated management system.

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ISO 50001 certification

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Tyrone Adu-Baffour

The environmental engineer looks back on more than 10 years of experience as a project engineer for energy efficiency and energy management as well as in the field of sustainability. He is a DQS standards expert and product manager for energy and climate management, as well as an auditor for the ISO 9001, ISO 14001 and ISO 50001 standards.