Affordable home power meters underestimate consumption, study finds


Espoo, Finland — (METERING.COM) — July 15, 2009 – Affordable end-user electricity meters used for measuring the consumption of domestic appliances and electronic equipment often underestimate the power consumed, researchers at the Helsinki University of Technology TKK have found.

In a test of nine power meters available in Finland, all but one widely available from general electric and discounts stores and all but one in the price range €10-20, the average errors were found to range from just below 3 percent to almost 19 percent, with the majority of the measurements underestimating the load.

In some cases, some devices had more than 25 percent error.

However,  the accuracy of the meters was not dependent on the price of the device. Two of the cheapest meters had among the lowest errors while some of the more expensive meters had among the largest errors. The best devices can reliably be used to measure both very small stand-by loads and big loads.

The meters tested were the Lidl PM333 (price €13, average error 12.2 percent), Clas Ohlson EMT707C TL (€14, 3.2 percent), Technoline Cost control (€14, 2.6 percent), Hong Kong FHT”9999 (€13, 17.8 percent), FHT”9999 (€20, 18.7 percent), Velleman NETBSE M2 (€20, 6.2 percent), Clas Ohlson PM300 (€20, 15.3 percent), and Motonet PM300 (€20, 12.2 percent).

The ninth meter, the Onninen REV”TS”JD, and the most expensive (€40), broke down during testing. While the average error for bigger loads was excellent (1.5 percent), the device failed to register a small computer standby load, however.

For comparison two more expensive meters (Plogg Blu v2.0 and Christ”Elektronik CLM200), not commonly available or of interest to consumers, were also included in the test sample. The average errors of these meters were 1.5 percent and 5.6 percent respectively, with the latter reduced by poor performance with the smallest load.

Reseachers Lassi A. Liikkanen and Tatu Nieminen who conducted the tests, say that the range of power consumption meters available for end users is wide but the technical quality of such inexpensive power meters is variable. However, by selecting the right device, a consumer can acquire an accurate meter affordably. Moreover, with inexpensive devices there are usually drawbacks. In the tested devices, the biggest problem was usually the embedded display, with viewing angles that made the meters difficult to read and thus potentially hindering their usage across the physical locations of a household.

“In future, we expect to see very different, much more flexible solutions for addressing the needs of measuring electricity consumption at home,” say Liikkanen and Nieminen.

The study was a part of the European Union funded BeAware project aimed to improve people’s awareness on energy consumption. The project is co-ordinated by Helsinki Institute for Information Technology (HIIT), a joint research institute of Helsinki University of Technology TKK and the University of Helsinki for basic and strategic research on information technology.