How much electricity does an AC consume? Like all typical MBA answers - it depends. I’m going to help you understand which type of AC to buy based on your usage patterns.
The summary of this video is -
A 3 star AC is sufficient if you run your AC for less than 6 months in the year and you run your AC for less than 12 hours in that period
Go for a 5 star AC if you plan to run the AC throughout the year for all 12 months or if you plan run your AC for 12-24 hours during the period you use it (even if it is 3-6 months in the year)
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Follow along to understand how I came up with this summary.
Let’s talk about inverter ACs - because that’s where most manufacturers are moving towards. For the sake of consistency - let’s use a 1 Ton AC for the comparison and LG as a brand so we can understand the trend - the same will apply when you are comparing different brands. Typically, you need 1.5 / 2 tons for larger rooms and lesser size like 0.8 ton for smaller rooms. I won’t go into detail on this - you can see the sizes on the screen
First let’s talk about the unit consumption per hour. 5 star ACs consume less units per hour compared to 3 star ACs. How to determine that? Most Air condition manufacturers will publish a power savings guide as you can see on the screen. This guide will tell you a few things - but we will use the electricity consumption per year in our calculation. Now this electricity consumption is measured for 1600 hours. So based on this - units consumed per hour is shown on the screen.
Now that we have the units consumed per hour - let’s calculate how much your electricity cost will be per month - assuming a few different scenarios. That you are running the AC for 6 hours per day, 8 hours per day (i.e., through the night), 12 hours per day, 16 hours per day and 24 hours per day. Assuming a per unit cost of Rs. 8/kwh, we get the per month increase in electricity that you could see as shown on the screen. For example - if you are running your AC for 12 hours a day, your monthly electricity bill increase will be 1225 for a 3 star and 1029.6 for a 5 star AC. So as you can see - the 5 star rating ACs give you atleast a 16% saving in electricity.
These costs assume that you are not freezing yourself and are running the AC at approximately 24 degree centigrade. If you run the AC at a lower temperature OR your outside temperature is too high OR you stay on the top floor, the effort your AC has to do is higher, so your cost will be higher.
Based on this calculation, does it make sense to buy a 5 star AC all the time? No - you do pay a higher upfront cost for a 5 star AC compared to a 3 star AC. So it’s also important to understand how long it will take for you to recover that upfront cost, isn't it? So in the example we took - the two LG ACs of 1 Ton 3 star and 5 star have a cost difference of about Rs. 3000.
Based on the above calculation, considering there is a 16% saving in electricity per month, let’s see how many months it will take for us to recover the Rs. 3000 difference in upfront cost. So if you go for a 5 star instead of a 3 star, if you run your AC for 8 hours a night, every single day through the year, it will take you 23 months (or close to 2 years) to recover the upfront cost).
But this is not all. We don’t run the AC through the year typically - especially when you stay in cooler areas! For example, in a place like Bangalore - I may only run it for 3 months a year. In which case, if I am running it for 8 hours in the night only - it’s going to take me 7.5 years to recover the difference in upfront cost, not calculating the interest on the money paid upfront :D. So generally speaking, lower the time to recover your upfront cost, the better.
So to summarize -
A 3 star AC is sufficient if you run your AC for less than 6 months in the year and you run your AC for less than 12 hours during that period
Go for a 5 star AC if you plan to run the AC throughout the year for all 12 months or if you plan run your AC for 12-24 hours during the period you use it (even if it is 3-6 months in the year)
Very good article