Come winter, everyone starts using water heaters at home. So water heaters or geysers are popular home appliances in almost every Indian home.
But do you know that geysers can consume a lot of power?
For example, a 3Kw geyser can consume up to one unit of electricity in 20 minutes.
Therefore, the Bureau of Energy Efficiency (BEE) has made it mandatory for water heater manufacturers to rate their products as per BEE requirements.
Read: BEE Star Ratings
How do BEE rate water heaters and geysers?
BEE mandates the star rating of water heaters and geysers on a scale of 1-star to 5-star, with 5-star being the most energy-efficient. The rating process is complex. Fortunately, users need not break their heads over it because manufacturers are mandated to affix the BEE star labels on each product, making it easy for users to know the rating.
Let us understand how manufacturers rate water heaters and geysers.
The BEE star ratings are calculated using the Standing Loss concept. Standing Loss is the energy the geyser consumes when not in use. For example, it is the energy the geyser consumes when remaining connected to a power source for 24 hours while containing a full tank of hot water at 450C. The reasoning is that the water gradually loses its heat when not consumed by the user. This concept demonstrates the water heater’s insulation or heat retention capacity.
As a user, how would you determine the standing loss? There is no need for you to calculate anything. The BEE star label provides this information.
Here is the BEE star rating valid from 01.01.2019 to 31.12.2022. Though BEE has not extended the validity dates, they are expected to do so soon.
|6||0.387 < SL <= 0.426||0.352 < SL <= 0.387||0.320 < SL <= 0.352||0.291 < SL <= 0.320||<= 0.291|
|10||0.485 < SL <= 0.534||0.441 < SL <= 0.485||0.401 < SL <= 0.441||0.365 < SL <= 0.401||<= 0.365|
|15||0.558 < SL <= 0.614||0.507 < SL <= 0.558||0.461 < SL <= 0.507||0.419 < SL <= 0.461||<= 0.419|
|25||0.680 < SL <= 0.748||0.618 < SL <= 0.680||0.562 < SL <= 0.618||0.511 < SL <= 0.562||<= 0.511|
|35||0.777 < SL <= 0.855||0.706 < SL <= 0.777||0.642 < SL <= 0.706||0.584 < SL <= 0.642||<= 0.584|
|50||0.898 < SL <= 0.988||0.816 < SL <= 0.898||0.742 < SL <= 0.816||0.675 < SL <= 0.742||<= 0.675|
|70||1.019 < SL <= 1.121||0.926 < SL <= 1.019||0.842 < SL <= 0.926||0.766 < SL <= 0.842||<= 0.766|
|100||1.164 < SL <= 1.280||1.058 < SL <= 1.164||0.962 < SL <= 1.058||0.875 < SL <= 0.962||<= 0.875|
|140||1.310 < SL <= 1.441||1.191 < SL <= 1.310||1.083 < SL <= 1.191||0.985 < SL <= 1.083||<= 0.985|
|200||1.456 < SL <= 1.601||1.323 < SL <= 1.456||1.203 < SL <= 1.323||1.088 < SL <= 1.203||<= 1.088|
BEE has mandated that all storage water heaters with capacities from 6L to 200L must evidence the star rating mandatorily on each appliance.
Please note that the BEE star ratings do not apply to instant heaters and geysers with capacities of less than six liters.
What about solar water heaters?
Consumers have increasingly started using solar water heaters. So BEE has included solar water heaters in its voluntary appliances list. Therefore, manufacturers need not mandatorily display the star ratings on their appliances. However, they can do so if they wish to.
How do we estimate the BEE star ratings of solar water heaters?
The ratings for solar water heaters are estimated based on the appliance’s system efficiency. The calculation is complex and denoted by this formula.
The rate of change in the energy of the water in the storage tank is equal to the rate at which the energy is supplied to the water minus the rate of energy loss from the water to the ambient air.
But, this calculation requires making the following assumptions.
- The average temperature of the stored water is 500C.
- The average temperature of the ambient air is 250C.
- The average solar radiation incident on the solar collector panel should be 700W per square meter.
BEE has proposed the following star ratings for solar water heaters. Since solar water heaters are in the voluntary appliances category, BEE has not yet extended the validity. Nevertheless, here are the applicable ratings for solar water heaters valid from 14.12.2019 to 31.12.2021.
|Star Label||System Efficiency|
|1-star||40 < SE < 45|
|2-star||45 < SE < 50|
|3-star||50 < SE < 55|
|4-star||55 < SE < 65|
|5-star||65 < SE|