Many types of LEDs have not been designed to be used with dimmers, but even those that did generated false readings in some meters

Smart meters can provide electricity readings up to six times higher than actual levels, according to a new study. These meters have passed standards tests, however these tests have failed to identify faults because the meters contain components not designed to measure some of the latest devices in use, and the standards have not yet caught up with this.

It’s often been a mantra of energy efficiency that “what gets measured gets saved”. But what if the meters used for measuring energy give faulty readings? Two recent market studies have found that such meters are relatively common.

One study by scientists at the Dutch University of Twente found that smart meters can provide electricity readings that are up to six times higher than actual levels.

This unreliability is especially prevalent when monitoring the outputs of LED lighting when they are combined with dimmers.

Tests found that 60 per cent of the meters tested frequently gave results as much as 582 per cent (almost six times) the actual energy use, while some of the meters under-recorded consumption by up to 30 per cent.

Many types of LEDs have not been designed to be used with dimmers, but even those that did generated false readings in some meters. The electricity being consumed has an erratic waveform and many of the meters tested were unable to process this, which caused the inaccurate results.

“Okay, these were laboratory tests, but we deliberately avoided using exceptional conditions,” University of Twente PhD student Cees Keyer said. “For example, a dimmer and 50 bulbs, while an average household has 47 bulbs.”

The researchers dismantled the energy meters tested and discovered the ones giving excessively high readings contained a Rogowski coil current sensor. The meters giving a lower than actual deviation were fitted with a Hall effect-based current sensor.

Frank Leferink, professor of electromagnetic compatibility at the University of Twente, said: “The energy meters we tested meet all the legal requirements and are certified. These requirements, however, have not made sufficient allowance for modern switching devices”.

The standardised test for meters does not make allowance for waveform-contaminating power-consuming appliances. As a result, according to the researchers, it is an unsuitable method for testing meters. Professor Leferink and Mr Keyer advise any consumers who doubt their meter readings to contact their supplier.

In Holland, 750,000 of these meters have been fitted. The network company responsible, Liander, commented that the problem centres on meters installed between 2012 and 2014, with large companies most likely to be affected.

However, households with solar panels and electric cars are also likely to have been hit. The Dutch consumers association said that Liander “should be actively looking for the faulty meters and looking at eventual compensation”.

Millions of similar meters may be installed around the world. The only way for their owners to know if they contain the misleading current sensors would be to consult the manufacturer. They would then have to replace the meters at their own cost under present circumstances – an unacceptable case of testing standards failing the marketplace.

The study, Static Energy Meter Errors Caused by Conducted Electromagnetic Interference, was published in the scientific journal IEEE Electromagnetic Compatibility Magazine.

Industrial hot water meters

At the other end of the market, in industry, meters can also be inaccurate due to the temptation to cut costs by purchasing a cheap metering solution.

Martin Wardell, managing director of data-logging software and meter company MWA Technology, says problems arise due to the use of low-quality products for metering hot water.

Wardell claims that the use of sub-par meters, whose life expectancy is extremely low, is “an indictment of the lack of care taken by consulting engineers” who fail to recommend or install heat meters using ultrasonic flow sensors. This type of meter will operate accurately for up to 20 years.

Leading manufacturers of energy meters, including Kamstrup, Diehl/Hydrometer and Itron, do not use mechanical flow parts/meters, instead opting for ultrasonic flow parts.

“What we are seeing more during our site visits is the combination of mechanical parts meters integrated alongside ultrasonic meters, resulting in the performance breakdown of the mechanical counterpart and the inevitable leaking,” he said. “Picking the right meter from the start saves money and complications.”

He puts the blame on estimators in building services and system integrators.

“They have been weaned on this low-cost solution and have the approach that as long as they perform for 12 months, they can wash their hands of any future issue.

“While many consulting engineers have realised that heat meters must be MIS Class II certified, when it comes to specifying water meters they specify WRAS approved and MID certified but they fail to specify the accuracy class. This should be R400 minimum, which are UK water utility grade meters.”

Standards for all energy meters can be found on this European Union website.

David Thorpe is the author of a number of books on energy efficiency, sustainable building and renewable energy. See his website here.

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