Analysing your company’s weekend consumption for ISO 50001: how to find background use
Analysing weekend consumption means comparing energy use at weekends and outside working hours with use on working days. That shows background consumption: energy that keeps running when there is no production or activity, such as compressors, lighting or heating that never switch off. With hourly data from your meter, you can find this in a day or two. The analysis fits into the energy review of ISO 50001 (clause 6.3) and provides input for your significant energy aspects. The standard does not prescribe this analysis. It is a method you can use to meet the energy review requirement.
Background consumption is not a fault in the installation. It is a sign that a system is not matched to how the business operates. Often the solution is a timer, a sensor or a setting. Not all consumption outside working hours is waste: cold rooms and server rooms need to keep running.
Why weekend consumption matters
Many energy analyses look at the annual total. That hides the pattern behind the average. Take a company that uses 30 percent of its electricity at night and at weekends. That has a different problem from a company that wastes a lot during the day. The weekend profile shows which share of consumption keeps running.
For ISO 50001, this is useful for two reasons. It helps you justify the energy baseline, because you know which part of consumption is fixed. It also gives you a measurable objective: reducing standby consumption. See the energy baseline and the energy performance indicators (EnPIs) for the rest of the chain.
Step by step: analysing weekend consumption
Get hourly data
Ask your grid operator or energy supplier for quarter-hour or hourly values from your electricity meter. With a smart meter or a large-consumer connection, these are usually available. If you do not have them, install a temporary meter. As a rule of thumb, you need four weeks of data, preferably without public holidays or major shutdowns.
Split the week into blocks
Divide each week into working days and weekend. Within the working days, split into morning, afternoon and evening. Add night as a separate block. This is a fixed division that you apply the same way every time.
Calculate the average per block
For each block, take the average consumption per hour in kilowatt-hours (kWh). Compare the weekend with the working-day evening and with the night. If the weekend average is close to the night average, you have a fixed base load. That is the part you break down next.
Find the peak and the trough
Look at the highest and lowest values. A base load that is equally high every night points to equipment that is always on. A peak on Saturday points to an activity you did not expect, such as a cleaning crew or a process that keeps running.
Link to the installation
Put the findings next to a list of devices and installations. For each base load, ask: what runs here, and why? That is the step from analysis to action.
Record and repeat
Save the table as part of your energy review, and repeat the measurement after a measure. That way you can later show what changed.
Example: a bakery with two ovens
The table below is a fictional example of a bakery with two ovens that run on working days and stand idle at weekends. The figures are invented and not intended as a benchmark.
| Block | Average consumption per hour | Interpretation |
|---|---|---|
| Working day morning | 120 kWh | Production active |
| Working day evening | 75 kWh | Winding down and cooling |
| Working day night | 42 kWh | Base load, cold rooms and lighting |
| Weekend day | 40 kWh | Almost equal to night, no production |
| Weekend night | 39 kWh | Standby and cooling |
In this example, the background consumption sits in the base load. The weekend value is almost equal to the night value on a working day. Part of it is needed, because cold rooms must keep running. Another part is avoidable, such as lighting in the storage area and equipment on standby.
The calculation: 40 kWh per hour over 48 weekend hours is 1,920 kWh per weekend, just over 99,000 kWh per year. If a quarter of that is avoidable, that saves about 25,000 kWh per year. The action: a timer for the lighting and a submeter on the cold rooms, to separate the two. That measure returns in the action plan.
What the auditor wants to see
At the certification audit, the auditor checks whether your significant energy aspects are backed by data. A weekend analysis shows that you look beyond the annual total. The auditor wants to see:
- which period you used and why it is representative
- how you defined the blocks and whether that is consistent
- which actions have come out of the analysis
- whether the result was discussed in the management review
Common mistakes
Looking only at the weekend average. That hides the Saturday peak. Always split by block.
Including public holidays. A public holiday resembles a weekend and distorts the comparison. Remove them or mark them.
Forgetting lighting. Lighting is often a silent item that stays on outside working hours. Include it in the analysis.
Not assigning an owner. A background consumption finding without someone responsible gets left behind. Link every finding to a person and a date.
Measuring only once. Standby consumption returns after a renovation or new equipment. Repeat the measurement at the annual energy review.
How does this fit the EED and the energy saving obligation?
A weekend analysis is also useful outside ISO 50001. The energy saving obligation (Energiebesparingsplicht) requires you to carry out measures with a payback period of five years or less. A timer for lighting often pays back within that period. For the EED audit obligation, the analysis provides data for the energy consumption profile in the audit report.
Frequently asked questions
Do I need a smart meter? Not necessarily. Hourly data from the grid operator or a temporary meter is enough. A smart meter makes it easier to check the data every week.
How much standby consumption is normal? That depends heavily on the installation, the sector and the age of the equipment. There is no universal benchmark. Compare with your own baseline and with an earlier measurement.
What if I have no weekend production but still use energy? Then that is exactly the point of the analysis. Consumption without production is the first candidate for a measure.
Is this part of ISO 50001 or a separate analysis? It belongs to the energy review of ISO 50001, but you can also carry it out separately. For certification, you must link the result to your significant energy aspects and your action plans.
More information
- Energy review (ISO 50001): the full analysis, step by step
- Energy data measurement plan: which data you collect and how often
- Significant energy aspects (SEUs): how you choose the largest consumers
Sources
- ISO 50001:2018 : the standard in which the energy review is set out
- RVO, substantive requirements for the energy audit report : what an audit report must contain, including the consumption profile