[Gansan]

I think unless one intends to run multiple Acs for longer durations on a daily basis, the five star rated inverter ACs do not make sense. The cost difference between it and a lower star rated one will almost certainly not be recovered during the life time of an AC, which I suppose can be taken as ~ 8 - 9 years.

[Aroy]

Originally Posted by Gansan

I think unless one intends to run multiple Acs for longer durations on a daily basis, the five star rated inverter ACs do not make sense. The cost difference between it and a lower star rated one will almost certainly not be recovered during the life time of an AC, which I suppose can be taken as ~ 8 - 9 years.

It all depends on
. Reduction in electricity consumption/hr = E
. No of hours used per season = H
. Cost of electricity = R

Now in our case
E = 0.5KW (between Hitachi 3* and Daikin Inverter)
H = 15 x 30 x 6 (Hours, days, months) = 2700
R = 7.25

So saving is 9787.5 ~ Rs.9,800/ per season
The cost differential is 45-25=20K, so we break even in about 2 years.

Now the point is that the rates of electricity are rising monotonically. I have data from 2002. The unit rate has increase from Rs. 3.38/unit in 2002 to Rs.7.78 in 2014 (Divide the units billed by total demand - includes all taxes and subsidies). So you can expect the rates to double in another 10-12 years (if not sooner), and that reduces the break even time to a year.

If you have to run the AC's on generator, then
. At Rs.20/unit you break even in a year
. With lower EER you need less generator capacity.

So on the whole Inverter AC make a lot of sense in long term.

[vw19d]

Originally Posted by Gansan

I think unless one intends to run multiple Acs for longer durations on a daily basis, the five star rated inverter ACs do not make sense. The cost difference between it and a lower star rated one will almost certainly not be recovered during the life time of an AC, which I suppose can be taken as ~ 8 - 9 years.

Well, from whatever analysis I have done, apart from the savings on electricity, another important reason why an inverter AC makes sense is the better life of its compressor. A non inverter AC's compressor can only be switched off/ on whereas that of an inverter AC can be run at varying speeds. Obviously, turning off & on at regular intervals is worse than a prolonged running at a lower speed. So, I reckon, the life of an inverter AC is going to be longer than a star rated unit.

[khoj]

It's not that straight forward, there are a lot of components that can affect the life of the units. Besides the fixed speed compressors are pretty rugged, work on lower pressures with a soft start & get to cool down after a bit besides lasting for donkey's years. The DC inverter's compressors are exposed to higher working pressures, always on so more wear n tear and prone to getting dissed by their logic controller cards which are not very happy sitting outside under our Sun.

Mechanical stuff is always simple and best, start adding electronics and a different story emerges.

Originally Posted by vw19d

So, I reckon, the life of an inverter AC is going to be longer than a star rated unit.

[Gansan]

My usage is 6 hours a night for about eight months a year. So I suppose it will take about six or seven years to break even if I choose an inverter AC.

Also I am not entirely convinced about the 500W per hour difference in consumption. Even my ordinary Samsung window unit runs continuously for the first 90 minutes or so, and then starts to cut off intermittently. I suppose it will consume about four units for the six hours. An inverter unit may consume a couple of units less. But the difference in price between it and an ordinary unit is enormous. Like between a petrol and diesel car!

But if I have to run three ACs for ten hours or more a day for eight months in a year, that will be a different picture.

[khoj]

Hi Gansan, you will be surprised to know that there are inverter units that have a difference of 500W in their rated consumption what to talk about difference they have from fixed speed units consuming 2 units per hour on average for a 1.5 ton unit.

Originally Posted by Gansan

Also I am not entirely convinced about the 500W per hour difference in consumption.

[avisidhu]

Originally Posted by lurker

you should install something like this on your rooftop.
...
AC will work easier and temps will be cool and steady throughout the year.

Hey Lurker, this may be a bit off topic, but since you've invested some thought into this process, what would you suggest might be a good, cost effective way to cool a rooftop around 2500 sq feet?

The house at my hometown is a virtual furnace in summers thanks to the large surface area of the rooftop and no second floor constructed. I intend to do something about it next time I visit.

Suggestions on the same most welcome.

[sourabhzen]

Originally Posted by avisidhu

Hey Lurker, this may be a bit off topic, but since you've invested some thought into this process, what would you suggest might be a good, cost effective way to cool a rooftop around 2500 sq feet?

The house at my hometown is a virtual furnace in summers thanks to the large surface area of the rooftop and no second floor constructed. I intend to do something about it next time I visit.

Suggestions on the same most welcome.

There are various under/over deck roof insulation methods that can be employed. Most cost effective way is to do inverted earthen pot (or 'kullarhs') insulation. You will find enough information on the internet for the same. Others include reflecting porcelain tile roof, reflective paints etc. The insulation will definitely improve the heat situation but they will not be as effective as having another floor on top.

[kalpeshc]

My folks at my native place used to apply a temporary solution which I think was just extremely white limestone paint (chuna) kind of a material (although not actual limestone). It used to cost around 200-300 bucks for a surface area of around 800 sq. ft. One has to mix the power in water and spread using a regular broom! The only thing it was good at was reflecting sunlight (it was very bright) and it was water soluble, so a temporary fix. If it rains, it would wash away. Ask your local paint store for this. It reduces the overall temperature by at least 5-6 degrees IMHO.

[amitpunjani]

I am planning to purchase couple of Window Ac. During discussion with dealer a new name cropped up "Zamil" according to him, its rated above O General AC. Its one of top running brands within Middle East.

Any reviews on forum about this brand?

[YVES]

After 9 years fan of LG outdoor unit stopped,
Had to spend 1800 for repairs.
I casually asked the mechanic on the best buy in market for Split AC in current market. He told Daikin and stay away from inverter AC as any small issue will set back by at least 7-8K and there are 70% chances of korean makes failing due to heavy cost cutting and they maintain dual pricing and supply different oudoor units (cheaper material used) unless someone is knowledgeable while purchasing.
I could see it in the LG unit durring repairs which is old enough and better than the ones available today.

[Aroy]

Originally Posted by avisidhu

Hey Lurker, this may be a bit off topic, but since you've invested some thought into this process, what would you suggest might be a good, cost effective way to cool a rooftop around 2500 sq feet?

The house at my hometown is a virtual furnace in summers thanks to the large surface area of the rooftop and no second floor constructed. I intend to do something about it next time I visit.

Suggestions on the same most welcome.

Any white shiny paint will do.

Another solution is to cover the terrace with soil and grow grass. Of course you have to first waterproof the terrace, line it with polythene sheet (heavy duty), and then add soil. Finally transplant grass. The soil and water will keep the rooms below cool.

[akhil_007]

We have been using dulux weather shield white paint on roof top. Its very effective in keeping the house cool. Lasts for 4-5 years easily. Might cost around 10k for your house.

[Thad E Ginathom]

Heat proofing should at least pass the foot test. I know that, on a summers day, all I could do on our terrace was hop about and even that hurt. After the paint was applied, I can even stand still up there.

Huge difference, but I guess I'm willing to believe that any white paint might have been effective too.

[drsingh]

Originally Posted by Thad E Ginathom

Heat proofing should at least pass the foot test. I know that, on a summers day, all I could do on our terrace was hop about and even that hurt. After the paint was applied, I can even stand still up there.

Huge difference, but I guess I'm willing to believe that any white paint might have been effective too.

What about Styrofoam sheets on the ceiling inside? That's how concrete walls are insulated anyway.