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Different energy efficiency performance of air conditioners could mean a difference of several hundred dollars in annual electricity charges - CHOICE # 463

  • 2015.05.14

In the test on 15 models of window-type air conditioner, the Consumer Council found difference in their energy efficiency performance - the difference between samples of the highest and the lowest energy efficiency is up to 21%, and the difference in estimated annual electricity cost can be as high as HK$344.

13 samples are qualified for the top Grade 1 rating under the current grading standard, i.e. the most energy efficient. However, only 4 would still qualify for the Grade 1 rating when evaluated against the Council's test results and the new grading standard to take effect in November this year.

The test was conducted by an independent local laboratory commissioned by the Council. 15 models of the commonly called "1.5 horse-power" cooling-only window-type air conditioner, ranged in price from HK$3,588 to HK$6,130 were tested. Overall performance was rated based on: accuracy of claimed cooling capacity i.e. how close the measured cooling capacity was to its claimed value (10%), energy efficiency (50%), noise level (25%) , ease of use (10%), enclosure sweat and condensate disposal (5%).

According to the tests and on a 5-point scale, 2 samples scored 4.5 points, 11 samples 4 points, and the remaining 2 samples 3 points.

In respect of energy efficiency performance, the international standard ISO 16358-1 was adopted to calculate the Cooling Seasonal Performance Factor (CSPF) of each sample - higher CSPF value means higher performance in energy efficiency. The CSPFs of the 15 samples ranged from 2.44 to 3.09. Projecting on the basis of the CSPF values, the most energy efficient sample would save around 21% electricity annually compared with the least energy efficient sample.

Translated into annual electricity charges, assuming an air conditioner operates for 12 hours a day for 180 days in a year at the tariff of HK$1.2 per unit of electricity, electricity charges for the samples varied from an estimate of $1,243 to $1,587 - a difference of HK$344. The actual electricity charges depend on factors like the actual cooling load and running hours, etc; and if more than one air conditioner is in use, the difference in electricity cost would be greater.

Under current legislation and as prescribed under Mandatory Energy Efficiency Labelling Scheme (MEELS), energy label is required to be affixed on air conditioners for supply in Hong Kong. Grading for energy efficiency performance is from Grade 1 to 5, with Grade 1 having the best performance. 13 out of the 15 samples are labelled as Grade 1 while the remaining 2 are labelled as Grade 2. While all 13 Grade 1-labelled samples attained Grade 1 performance level in the test, 1 Grade 2-labelled sample was found to attain only Grade 3 performance.

Although the calculated grading of that one sample was different from the labelled grading, the discrepancy is however within the tolerance margin of 10% allowed under the MEELS and common international practices.

To encourage suppliers to introduce higher energy efficient products, the Electrical and Mechanical Services Department (EMSD) will implement a new grading standard from 25 November this year applicable to air conditioners, refrigerators and washing machines. Measured against the new standard, and calculating on the basis of the Council's test results, only 4 samples can remain in the Grade 1 level, while the rest of 11 samples will all be downgraded. The 2 Grade 2-labelled samples will even drop to Grade 4 level.

EMSD estimated that implementation of the new grading standard would achieve an annual saving of electricity consumption by 300 million kilowatt-hour and a reduction of 210,000 tonnes of carbon dioxide emission per year. Design of the new grading energy label is the same as the existing one, but with addition of "U1" to precede the reference number on the new grading energy label for identification by consumers.

As far as cooling capacity is concerned, a higher value means faster in cooling speed and higher in cooling ability. In the test, cooling capacity of the samples ranged from 3.3kW to 3.8kW. The cooling capacities of 13 samples obtained from the test were close to the claimed values. Variations detected between the test results and values claimed by manufacturers were from 7.2% lower to 1.7% higher than the claimed value. Although the variations were within the 10% tolerance under international practices, the Council is of the view that consumers may expect that manufacturers would ensure the cooling capacity of the products is not lower than their claimed values.

The dehumidification performance of the samples also varied. 4 samples used around 32% of the cooling capacity for dehumidifying resulting in a relatively faster pace in dehumidification. 3 samples only use around 25% to 26% of the cooling capacity for dehumidifying.

Quietness is another important factor in consumer choice of the appliance. In the test, under indoor environment, 6 samples scored 4 points; 6 samples 3.5 points, and the remaining 3 samples 3 points.

In respect of safety, all samples passed a series of safety tests (with reference to the international standard IEC 60335-2-40) which included amongst others, leakage current and earthing continuity.

In the event of air conditioner mal-functions, provision of effective maintenance and repair services by the agents can prolong the product's life-span. Among the test models, the warranty period ranged from 1 to 3 years for the entire new products, while compressors generally enjoy a longer warranty period, commonly for 5 years. 2 samples claimed life-long warranty period for their compressors. Except 1 model which does not provide continued maintenance, the other 14 offer maintenance renewal at an annual fee from HK$400 to HK$750.

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