Skip to main content

Latest Test on 13 Thermo Ventilators Showed Big Disparity in Heat-up Speed Clothes Drying Time and Energy Efficiency Could Vary by Onefold

  • 2022.11.15

With winter just around the corner, a multifunctional and energy-efficient thermo ventilator can serve several purposes, from keeping the bathroom heated and toasty to boosting ventilation and drying clothes. Since previous tests on thermo ventilators in 2015 and 2017, the Consumer Council recently tested 13 models of thermo ventilators and bathroom heaters, including portable models with hooks for easier mounting on towel rails in the bathroom. The results revealed the safety and performance of the tested models to be generally satisfactory. Other than 1 model, the rest achieved an overall rating of 3.5 points or more.

However, the warm air output temperature could vary by over 16°C amongst the tested models, while the drying time could also vary by more than onefold, thus resulting in the same variance in the electricity bill for clothes drying. Based on the results of the current test, when purchasing a thermo ventilator, consumers are reminded to consider foremost their purposes of use, then select an energy-efficient model which best fits their personal use. 

The Council and the Electrical and Mechanical Services Department (EMSD) commissioned independent laboratories to conduct tests on the models’ performance and safety respectively. Included in the test were 13 models covering 3 main types, namely 6 window-mounted and 3 ceiling-mounted thermo ventilators, and 4 portable bathroom heaters. The price ranged from $699 to $4,350, a huge disparity of over 5 times. One of the lower-priced models ($799) received the same overall rating of 4 points as the highest-priced model, once again reflecting that good quality products are available irrespective of their prices.

All But One Model Dried Clothes Within 8 Hours Yet

Electricity Bill Could Vary by Onefold

The performance test was conducted with reference to the national standard GB/T 22769, covering the test items of clothes drying, heating performance, air delivery rate, warm air output temperature, noise level, etc.

Taking into account Hong Kong's humid climate, the window-type and ceiling-type thermo ventilator models were tested for their clothes drying performance in a simulated bathroom within an environmental chamber at constant temperature and humidity. As the portable models did not have substantial claims to their clothes drying capability, they were not included in this test.

Apart from 1 model, the remaining 8 tested models were able to completely dry an identical amount of clothes within the set time limit of 8 hours, with the drying time ranging from around 3.3 hours to 6.4 hours, a variance of nearly onefold. The 3 ceiling types were found to perform better – all could complete the drying within 4 hours (3 hours 17 minutes to 3 hours 41 minutes), thus all received a satisfactory rating of 4 points. Among the 6 window types, only 1 model could complete the drying within 4 hours, a performance comparable to the ceiling types; 4 models took more than 5 hours, while 1 model could not even completely dry the clothes within the 8-hour time limit. In the latter case, the model’s heater automatically switched off at around 2 hours after the test began and only streamed cool air at the clothes for the next 4 hours. Eventually, its clothes-drying programme stopped automatically after 6 hours, at which point the clothes were only 65% dry. Therefore, this model received the lowest rating of 1.5 points only.

The better drying performance of ceiling-type models could be attributed to the fact that warm air was delivered from top to bottom, providing a more even drying effect for clothes under the air outlet. For window-type models, as the distance between the clothes and the air outlet varied, clothes further away from the outlet would require a longer time to dry.

In terms of clothes drying energy efficiency, the ceiling-type and window-type models were measured for their electrical power consumption in the drying test. Excluding the model which failed to completely dry the clothes in the time limit of 8 hours, 3 models (including 1 window-type and 2 ceiling-type models) were measured with the lowest power consumption, ranging from 3.2kWh to 3.7kWh. The most power-consuming model was found with a power consumption of 6.2kWh, which was almost twice as much as the best-performing model.

Based on the tariff of $1.8 per unit of electricity and the scenario where the thermo ventilator was used for clothes drying 15 times a month, the estimated monthly electricity bill for the most energy-consuming model would come to around $167.4 ($1.8 x 6.2 x 15), whereas that for the most energy-saving model was around $86.4 ($1.8 x 3.2 x 15), a difference of almost onefold.

In the light of the test findings, consumers who frequently use the clothes drying function of their thermo ventilators are reminded to choose a product with lower electrical energy consumption (i.e. more energy-efficient) to save energy and protect the environment. Furthermore, based on the Council’s test on thermo ventilators in 2017, a compressor type ceiling-mounted model was found to consume much less energy (0.7kWh) than the models which relied on warm air to dry clothes (2.4kWh to 10.8kWh). Therefore, consumers could consider using a dehumidifier solely for the purpose of clothes drying.

Warm Air Output Temperatures Varied by Up to 16°C

Over 5-time Difference in Temperature Rise Time

The room heating test simulated the heating performance of the models in a bathroom at a room temperature of 16°C in winter. The models were measured for their maximum warm air delivery rate and temperature, temperature rise range and speed of heating up a target object, and stability of input power, etc. The maximum warm air temperatures at the outlet were found to vary from 39.6°C to 55.9°C, a significant difference of 16.3°C. Overall, the window-type models generally had lower maximum warm air output temperatures (41.8°C to 44.2°C) as compared with the ceiling-mounted and portable models.

The models were also tested for heating up a target object placed 1.3m above the ground at the centre of the test room to measure and assess the temperature rise and heat-up speed. It was revealed that the average temperature of the targeted heating area ranged from 31°C to 54°C, while the temperature rise time (based on the temperature rise to 70% of a stable temperature) ranged from 5 minutes 50 seconds to 37 minutes 6 seconds, a variation of over 5 times. The heating performance of all models were rated 3.5 to 4 points which reflected satisfactory overall results.

Non-compliance with Safety Requirements on 2 Models
Labelling Information of 3 Models Fell Short of Standard

The safety test was conducted with reference to the latest requirements of the international standard IEC 60335-1, IEC 60335-2-30, etc. Test items included the construction, water resistance (ingress protection), power rating discrepancy, marking and instructions, etc.

The claimed water ingress protection ratings varied among the models and all models were able to pass the water resistance test. However, consumers are reminded that as the water ingress protection is only applicable to the external enclosure, water should not be sprayed onto the front panel, and the device should also be switched off before cleaning.

In terms of the construction, 2 window-type models failed to comply with the standard requirements for earthing continuity. The screw terminal of the metal motor casing of 1 model was secured to a plastic casing, but the plastic material would become aged and deform over time causing the earthing terminal to loosen. For another model, the earthing stud on the inner side of the metal casing could be accidentally loosened from the outside by a screwdriver, the earthing continuity could be as such undermined. However, as the body of window-type thermo ventilators is usually covered with a plastic front panel, users have a lower chance of accessing the external and internal metal casing. Therefore, it should not pose serious risk in regular use.

While 10 models met the required standard in displaying instructions and information, 3 models failed to comply with the standard requirements in that the instruction manual of 1 model omitted the warning against the use by people with special needs and to teach children not to play with the device, while another 2 models lacked warnings for not installing the bathroom heater in a position reachable by users while showering, 1 of these models even missed the information, including precautions about the installation position and distance, and not to use in a room with individuals with mobility issues, etc.

Furthermore, the input power of 2 models were measured to be 5.7% higher and almost 12% lower than their power ratings respectively, which exceeded the upper and lower limits (+5%/-10%) of the standard requirements, reflecting the need for improvement in the labelling.

When selecting, installing and using thermo ventilators and bathroom heaters, consumers should pay heed to the following:

  • Employ a registered electrical contractor for installation of ceiling or window-mounted type thermo ventilators to ensure safety. As these devices generally have a higher power rating, the power cable may need to be re-wired from the mains supply separately;
  • Portable bathroom heaters should never be placed near the bathroom sinks or bathtub that might be filled with water, to avoid the risk of electrical shock if the user is in contact with the water. Neither should the device be placed in an environment of high temperature or humidity, for instance, right atop of the water heater;
  • When drying clothes, never cover the air outlet with the wet clothes to avoid affecting its normal operation;
  • Utilise the timer function to avoid prolonged high power operation like warming or clothes drying. Remember to switch off the appliance when not in use to save power and ensure safety;
  • Users should clean the product regularly according to the user guide. Some dust filters with antibacterial claims need to be cleaned with a vacuum cleaner instead of water.


Download the article (Chinese only):


Consumer Council reserves all its right (including copyright) in respect of CHOICE magazine and Online CHOICE.