Portable energy loggers, or PELs, are compact, comprehensive test instruments that measure, monitor, and record an array of electrical parameters. They can be used to troubleshoot electrical systems and, more importantly, identify sources of energy and/or power wastage contributing to inflated utility bills, as well as excessive and unnecessary greenhouse gas emissions.[1]

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What Is a PEL?

A portable energy logger (PEL) is a small, lightweight electronic monitoring instrument with or without a display that collects electrical data pertaining to any combination of the following: voltage, current, frequency, power, energy, phase angle (cos φ, tan Φ, and power factor), total harmonic distortion (THD), and harmonics. For instance, the Chauvin Arnoux PEL103 Power/Energy Logger can measure:

  • Voltage AC/DC
  • Current AC/DC
  • Voltage ratio
  • Current ratio
  • Power
  • Energy
  • Phase (cos φ, tan Φ, and power factor)
  • Harmonics
  • DC network frequency

PELs are available with multiple inputs/ channels enabling them to collect data from several sources simultaneously. The Chauvin Arnoux PEL103 has three voltage inputs and three current inputs. Thousands if not millions of readings gathered via these inputs over the course of minutes, hours, days or months (model dependant) can be saved to the portable energy logger’s memory. PELs may be programmed to measure and save data on a sub-cycle basis or to record averages over a user-specified aggregation period.

In addition to logging data, some PELs support local or remote real-time monitoring. For example, it is possible to save up to 8GB of data to the PEL103’s memory card; however, this instrument also includes USB and Bluetooth interfaces for local real-time monitoring and an Ethernet interface for remote real-time monitoring.

Why Do I Need a PEL?

A portable energy logger will save you money. It will help you to optimise electrical systems, reduce energy consumption or waste and, therefore, decrease energy expenditure and carbon emissions. PELs will prove useful tools in the effort to meet the UK's 2050 net-zero target. 

Portable energy loggers monitor energy and power consumption. They can help identify operational issues, power supply problems (e.g. unbalanced three-phase supplies, poor power factor, and a high level of harmonics in the supply system), and sources of waste (e.g. out-of-hours equipment operation and inefficient lighting). The Carbon Trust estimates that 20% of a business’ yearly energy expenditure is squandered because of energy inefficient equipment, while a British Gas survey of 6000 SMEs found that 46% of electricity use occurs outside of normal business hours.[2]

Chauvin Arnoux estimates that significant savings can be made by implementing simple and expense-free policies, such as switching off office equipment after hours. They postulate that powering down non-essential office equipment at the end of the workday could result in energy savings of up to 12%. Moreover, switching equipment off over weekends and bank holidays could save the average SME £6000 a year![3] However, in order to make these savings, you first need to know where the wastage is happening and, secondly if any corrections you’ve made are having the desired effect. PELs, such as the PEL103, provide a solution to both these requirements.

What Should I Look For in a PEL?

Chauvin Arnoux’s Julian Grant recommends that individuals and/or businesses consider the following when deciding on a portable energy logger.

Measurement Scope

Most PELs will measure frequency, voltage, and current but you should check that your model provides true-RMS readings. You’ll also require an instrument that measures power, reactive power, and power factor, as well as energy usage.

Common in offices, variable speed drives, LED lighting, IT equipment, and UPSs are non-linear loads that all produce harmonics in the supply system. Julian Grant suggests that potential buyers pay particular attention to portable energy loggers’ harmonics measurements. He advises selecting an instrument, such as the PEL103, that measures harmonics up to the 50th order as these machines will provide meaningful results that can be used to trace the source of the harmonics. PELs that only measure the total harmonic distortion (THD) and/or the low-order harmonics will not be able to deliver the information required to make significant and effective changes.


To maximise energy savings, you will want to use your PEL in many different locations. This means the PEL must be suitable for use with a variety of electrical installations such as single-phase, split-phase, and three-phase systems. Incidentally, Chauvin Arnoux’s PEL103 is suitable for use with all these circuit types.


It is essential that your chosen PEL is compact to ensure it can be mounted in tight spaces such as switchboards and control panels. Furthermore, if you're going to use your PEL in multiple locations, it must be easy to install. If it takes too long or is too awkward to set up your portable energy logger, it's likely that you’ll cease using it before you've had a chance to recoup the cost of the instrument through energy savings.

Some PELs include features specifically designed to improve the ease and speed of installation:

  • Rogowski coils: these wrap around the conductor and measure current flow without making a direct electrical connection.
  • Voltage sensing magnetic probes: these are connected to MCB screw heads or other suitable connection points enabling voltage measurement without disturbing the wiring.
  • Magnetic back: quickly and securely mount the PEL on steel surfaces such as enclosure doors and walls. The PEL103 features a magnetic back.

Easy to Use

Simple installation should be complemented by simple operation. Julian Grant recommends that you choose a PEL with a large, easy-to-read display and a clear, logical user interface. He also suggests selecting a PEL that is supported by powerful and intuitive PC software designed for data analysis. Some PC software applications also facilitate remote monitoring via a laptop or computer. Our current Chauvin Arnoux PEL103 Offer includes FREE DataView Software as well as a FREE Android Tablet.

Memory Capacity

To gain real benefit from a PEL it must be left to monitor electrical parameters over prolonged periods of time. This means it is essential that your chosen model features a large memory from which relevant readings can be easily retrieved. The best solution to this is to invest in a portable energy logger with an SD card or slot, such as the PEL103 which is supplied with an 8GB SD card. Measurements stored on an SD card can be easily downloaded to a PC. Furthermore, these inexpensive memory cards can be replaced when they reach capacity, in effect providing unlimited data storage.


If you require real-time monitoring, significant attention needs to be paid to the type of connectivity supported by your PEL. More sophisticated models may include Wi-Fi or Ethernet for remote monitoring; while USB and Bluetooth interfaces enable local connections. The Chauvin Arnoux PEL103 offers both local and remote monitoring as it features Bluetooth, USB, and Ethernet interfaces.

Safety Rating

Often PELs will be installed in distribution boards. Therefore, it is essential that, as a minimum, your chosen portable energy logger has a CAT III safety rating (IEC 61010) and, if you intend to monitor three-phase systems, this rating is valid at 1000V. As the PEL103 has a safety rating of CAT III 1000V and CAT IV 600V (IEC 61010), it can be used in distribution boards to monitor three-phase systems.


The final recommendation Julian Grant makes is to consider the manufacturer and supplier of your PEL. Investing in a brand with a reputation for quality, such as Chauvin Arnoux, will save you money in the long term. Similarly, choosing a knowledgeable supplier, such as PASS Ltd/ tester.co.uk, that can be relied upon to provide expert advice and guidance after purchase will also help you get the most out of your PEL.

Further Information

The Chauvin Arnoux PEL103 Power/ Energy Logger has been mentioned frequently throughout this blog. For more information regarding this product please click here. Alternatively, to browse our complete selection of Chauvin Arnoux portable energy loggers and power quality analysers, please follow this link.

For more information about PELs, PQAs or any of our other energy and power monitoring equipment, please contact our Sales team on 01642 931 329 or via our online form.

[1] Information for this blog post was mainly gathered using the following sources:

Where additional sources have been used, separate references have been added.

[2] Chauvin Arnoux, Monitoring your way to higher profits, last accessed 06 May 2021 < https://cauk.tv/articles/monitoring-your-higher-profits/>

[3] Chauvin Arnoux, The Importance of Metering and Monitoring Energy Consumption, last accessed 06 May 2021 <https://cauk.tv/articles/metering-monitoring/>