What is Inverter Technology AC and How it is Different from BEE 5 star Non Inverter AC?

Air Conditioners are a pain point for most people in our country who are concerned about their electricity bills. The moment an air conditioner is added to the list of appliances used in a household, the electricity bills increase significantly. Although it is difficult to significantly reduce the “big” impact of an air conditioner on your electricity bills, but still some of it can be managed by choosing the right technology, doing the right installation/maintenance/operation and by doing the right insulation of the room where the air conditioner is used (more details in our articles listed at the end of this article).

When it comes to technology, there were not many available till sometime back. When BEE actively started analyzing and labeling the air conditioners, we got some good one in form of 5 star air conditioners. The latest and the most efficient technology that is available in market today is the Inverter Technology for air conditioners. Inverter technology is designed in such a way that it can save 30-50% of electricity (units consumed) over a regular air conditioner. And since 2016, BEE has started give star ratings to inverter technology ACs as well. However, let’s look at what is inverter technology and how is it different from a non inverter BEE 5 star rated ACs.

How does an air conditioner work?

For most people, air conditioner just throws cool air at the temperature one sets it at. But does it really work that way? In fact air conditioner during cooling process, takes the indoor air, cools it by passing it through evaporator and throws it back in the room. It is quite opposite to how our good old air coolers used to work. Air coolers used to take outside air, cool it with water and throw it in. But air conditioners just work on internal air. Along with evaporator air conditioner also has a compressor that compresses the gas (refrigerant) in the AC to cool it that in turn cools the incoming internal air from the room.

In a regular air conditioner:

The compressor is either off or on. When it is on, it works at full capacity and consumes full electricity it is designed to consume. When the thermostat reaches the temperature level set in the AC, the compressor stops and the fan (in AC) continues to operate. When the thermostat senses that the temperature has increased, the compressor starts again.

What is Inverter Air Conditioner?

The inverter technology works like an accelerator in a car. When compressor needs more power, it gives it more power. When it needs less power, it gives less power. With this technology, the compressor is always on, but draws less power or more power depending on the temperature of the incoming air and the level set in the thermostat. The speed and power of the compressor is adjusted appropriately. This technology was developed in Japan and is being used there successfully for air conditioners and refrigerators. This technology is currently available only in split air conditioners.

What is benefit of Inverter Technology?

Every air conditioner is designed for a maximum peak load. So a 1.5ton AC is designed for a certain size of room and 1 ton for a different size. But not all rooms are of same size. A regular air conditioner of 1.5ton capacity will always run at peak power requirement when the compressor is running. An air conditioner with inverter technology will run continuously but will draw only that much power that is required to keep the temperature stable at the level desired. So it kind of automatically adjusts its capacity based on the requirement of the room it is cooling. Thus drawing much less power and consuming lesser units of electricity.

Although air conditioner with Inverter Technology adjusts its capacity based on the room requirement, it is very important to install a right sized air conditioner in a room. Please make sure that you evaluate the room and air conditioner capacity before you make a purchase. Keep watching for this space as we are in process of creating a comparator for electricity savings in various air conditioners.

What’s the difference between Inverter Technology AC and BEE 5 star non inverter AC:

1. Inverter technology air conditioners are variable speed/ variable tonnage air conditioners and thus operationally they are quite different from regular air conditioners that have single speed compressors and single tonnage.
2. Inverter technology air conditioners adjust their speed/tonnage depending on heat load of a room. Whereas regular air conditioners do not.
3. Every room has a different heat load, even if they are of the same size. The heat load depends on various factors as we have listed on our article: Things that impact electricity consumption in air conditioners. To give you an analogy, every human being is different; even then the waist sizes of most trousers available in the market are fixed (leaving the ones with elastic). Inverter Technology AC is just like a trouser with an elastic waist that can adjust to the size. The other benefit is that even if the waist size increases or decreases, the trouser with elastic will adjust accordingly. Regular Air Conditioners are fixed size.
4. Based on the data on power consumption by BEE, Inverter ACs of BEE 3 star ratings are about 7% more energy efficient than BEE 5 star rated non inverter ACs.
5. The heat load in a room does not remain constant and it varies from seasons, varies based on number of people, varies between day and night, varies based on climate profiles of your location. To take the same analogy we mentioned above, the waist size increases or decreases with the amount of food one eats or the amount of exercise one does. So as a trouser with elastic waist can work well, an air conditioner with inverter tech can work well.

Power Consumption of Inverter and non inverter air conditioners.

Based on data from BEE in 2017, below is the representative (median) sample of power consumption of Air Conditioners of various tonnage and star ratings:

Are Inverter technology air conditioners slow in cooling?

Several people have concerns that Inverter Technology air conditioners do not cool well or cool slowly. However let us take this image as reference to understand how inverter AC works:

Non inverter ACs are fixed speed ACs, where as inverter ACs are variable speed ACs. Non inverter ACs have compressors that go “On” and “Off”. Whereas inverter ACs have compressors that are “On” all the time. As non inverter ACs are sized for peak summer heat load, they are over-sized all the other times (in fact most of the time people oversize even for peak summer season). The drawback of the same is that the AC “Over cools” most of the time. So if you set AC at temperature of 25, it will cool it down to 23 or 22. Now one would question: then what is the use of thermostat? Well the thermostat (in a non inverter AC) switches off the compressor when the outside temperature has reached 25. But a lot has happened before that. In an AC, refrigerant moves from liquid to gas (by taking heat from the room) and then back from gas to liquid as the compressor compresses it. But if the refrigerant is more and heat in the room is less (which happens in over sized AC), it does not get enough heat from the room to convert from liquid to gas and it keeps moving as liquid. Now when the thermostat detects temperature and switches off the compressor, the refrigerant still remains in liquid state and thus has capacity to take heat from room to convert to gas. And so it takes more heat from the room and cools the room below the set temperature.

In comparison, the inverter tech AC changes the flow rate of refrigerant based on the heat of the room. When heat is less, the flow rate is less, when heat is more, the flow rate is more. And it does not switch off the compressor ever. It just makes sure that if temperature setting is 25, it is maintained at that level.

So the difference is: non inverter AC would over cool as shown in the picture. Whereas inverter AC will cool optimum. And thus one may feel that inverter AC does not cool or is slow.

Is there a Window AC with inverter technology available in market?

No there is no window Air Conditioner with inverter tech available in market. Will they be available in future? We don’t know.

Are there Star Ratings for Inverter ACs?

In 2016, BEE introduced a new star rating standard for Inverter Technology ACs as well. Currently most models are in BEE 3, 4 and 5 Star rating ranges on BEE. In future (in 2018), BEE plans to merge the star rating standards of inverter and non inverter ACs. To know more about new star rating standards for Inverter ACs, you may read this page on our website: Understand What is ISEER and Star Labeling of Inverter Air Conditioners in India.

If you are looking for most energy efficient inverter ACs, here is the list:

Best Ten Energy Efficient BEE 5 & 4 Star Rated Inverter Air Conditioners in India

Click on a category button below to choose category.

To know more about BEE Star Rating of Inverter Air Conditioners check this page on our website: Understand What is ISEER and Star Labeling of Inverter Air Conditioners in India

Best Ten Energy Efficient BEE 3 Star Rated Inverter Air Conditioners in India

Click on a category button below to choose category.

Lesser known benefits of Inverter Technology

• Regular motors need 3-4 times more current (more than running current) at startup. So the inverter/generator size needed to run any AC or Refrigerator increases significantly. But Inverter Technology air conditioners and refrigerators have variable speed motors that start up gradually needing much lesser current at startup. Thus the size of inverter/generator required to startup is less. For e.g. A 1.5 ton fixed speed AC that runs at about 10 Amp current may need up to 30 Amp current at startup and thus a 5 kVA inverter/generator. But an inverter technology Air Conditioner needs about 6-7 Amp current and not much more at startup and thus a 1.5 kVA or 2 kVA inverter/generator is good enough to support it.
• Regular motors have much lower power factor. In commercial and industrial connections there is penalty for low power factor and rebates for higher power factor. An inverter technology motor will have power factor close to unity (or 1) which not only results in lesser electricity consumption but also help get rebates on better power factor.
• If you are planning to use Solar PV for air conditioner, then it is the best to use inverter technology air conditioner or refrigerator as it not only reduces the size of PV panels because it consumes lesser electricity, it also reduces the size of inverter to be put along with the PV panel.

Here is a short video for tips to buy the best air conditioner in India

Here is a calculator for Sizing Air Conditioners in India

Select your city, dimensions of room, usage hours and sunlight checkboxes to get our recommendations. The inputs are on the left size and our recommendations on the right side. Also please note that these calculations are for a regular room in a house. If the room size is more than 400 sq ft then it would be better to call an engineer to do the evaluation.

Air Conditioner Sizing Calculator for India

(Note: This calculator is for a residential setup. It assumes a regular room with some furniture, basic appliances and 4 people in the room. Please do not use the numbers for a commercial setup.)

Check this link to see Top Ten Air Conditioners in India for Electricity Savings: http://wp.me/p4hAhQ-4I

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