Enough of power cuts in the region I live and it became inevitable to buy an inverter/home UPS system. So I went ahead and did some very basic research before deciding upon buying the same. I am sharing the same over here in anticipation that it would help someone 
With loads of power backup options available in the market, it becomes quite a bit of an exercise to get to the right product. More so because of the aggressive marketing of the products, which may be misleading. Before even getting into the options, one needs to figure out the needs. For example, in my case I wanted a solution which would give a back-up of 2-3 hours for the following:
| S. No. | Equipment | No. of Units | Approx. Wattage / Unit | Total Wattage |
| 1. | Fan | 3 | 70 | 70*3 = 210 |
| 2. | CFL | 4 | 25 | 25*4 = 100 |
| 3.. | Notebook | 2 | 75 | 75*2 = 150 |
| 4. | TV | 1 | 120 | 120*1 = 120 |
| 5. | Miscellaneous (Modem, Router etc.) | NA | 50 | 50*1 = 50 |
| Total | 630 W | |||
So, I need a solution which can give me 630 W of power for 3 hours at a stretch (assuming I run all of the above for 3 hours). Now let’s do some high school physics calculations:
P (Power in Watts) = V (Voltage in Volts) * I (Current in Amperes)
Before we move ahead into the calculations, let’s clarify a couple of points:
What is the difference between an inverter and a UPS?
Well some think that these two are competing concepts, however the bottom line is that an ‘inverter’ is an equipment to convert Direct Current (D.C.) into Alternating Current (A.C.) where as an UPS (Uninterrupted Power Supply) is a circuitry which allows an instantaneous switch to the backup power source in case of a power failure thereby ensuring an uninterrupted power supply to sensitive equipments like a computer.
Now the only thing which needs an uninterrupted power supply in my list of equipments is the notebook, but that is anyway ensured by the notebook battery. So do I need a UPS? Well yes, I would want an uninterrupted internet connection in case of a power failure so I need the modem and router running in continuum.
Now that I know I need an inverter with UPS, do I need to look into anything else? Well yes, there are different types of inverters available in the market:
Square Wave Inverters: Popularly known as ‘Digital Inverters’ produce a Square Wave AC output which is not so great to run appliances as all the appliances are designed to run on a Sine Wave Alternating Current Pattern. Also, you would notice a humming sound in some of the appliances. Though electrical appliances would bear this, running electronic appliances over Square Wave is not at all recommended.
Sine Wave Inverters: These inverters produce the right wave pattern (Sine Wave) for which the appliances are designed. One can safely run most of the appliances on such current output.
Quasi Sine Wave Inverters: These fall somewhere in-between the above. I am not too sure about the internals. Also, didn’t find them in the market. But apparently they offer a low cost solution to run PCs and other electronic equipments on inverters.
Now what remains is the power storage medium, which, of course, is the battery. Again loads of options available which only confuse you. I didn’t think a lot over this and decided to go with an Exide Tubular Battery. Let’s have a real quick glance at the main options available relevant to inverters:
Standard Batteries: Loads of them available in the market. But they need maintenance i.e. putting in the distilled water on an ongoing basis.
Maintenance Free Batteries: While some claim they don’t need maintenance throughout their life-time, most of the maintenance free batteries need maintenance once a year or so.
Tubular Batteries: These batteries are superior in technology, construction and the quality of material used within. While you can figure out some nitty gritty here and here, they offer the following advantage:
- They are maintenance free.
- Long life (5+ years)
- Faster Charging
- More efficient
Though tubular batteries are a bit expensive, but considering their advantages I concluded that in the long-run, they actually turn out cheaper.
To wrap this up, let’s quickly get back to the calculations. So I needed a solution which could provide me with 630 Watts of power for 3 hours. Inverters available in the market are generally rated in VA/KVA.
Since, V*A=P, I need a 630 VA inverter. A very important point to keep in mind is the power factor. You would never get the rating mentioned in the inverter specifications. Considering a power factor of 0.8 (again figured out with some research) I would need an inverter with the following rating:
xVA * 0.8 = 630 VA
=> x= 630/0.8 = 787 VA
Luckily, for me we have 800 VA inverters available in the market, which perfectly fit to my needs. Note that this is a limiting factor w.r.t. the total wattage of appliances you can use. For instance I can’t run a 1000 watt appliance on an 800 VA inverter!
Now the battery. Inverter batteries are usually available in 12 V and are rated in Ampere Hours (AH). Since P=V*I and I need a backup for 3 hours,
630 W * 3 Hours = 12V * x (Ampere Hours)
=> x = (630 * 3)/12 = 157.5 AH
Again, luckily I discovered that we have batteries rated 165 AH in the market. So I decided to go with it.
Bingo! I have the details now. I need an 800VA inverter and a 165 AH battery for my needs. I just need to decide upon a brand based on the reviews.
Also, note that the above calculations are indicative. To quickly figure out how much back-up you would get while running a subset of the wattage considered at the time of buying, use the following:
Backup Time (Hours) = (Battery Voltage * Rating (in AH))/ Wattage required.
So if I just run 3 fans, i.e. 210 Watts, I would get a backup time of (on a fully charged battery):
12*165/210 = 9.4 hours
I can also run two moderate air coolers for about 7 hours. That’s sufficient for a night’s sleep
Comments
It was really informative and could be understood even by a layman.
Superb job done………
Great Work
Very Much informative
I would like to know about the Inverter loss and how much our eb Bill will shoot up if i directly connect all the lighting and fan load even when there is no powercut
Aswe some post MAN!!! really appreciate ur effort and your good intentions in sharing your reasearch GOD BLESS
Hey Amit,
Thanks for the post. It is very useful. Could you let me know where you bought Exide battery and Sukam Inverter. Contact number will be helpful. I asked someone base on Just Dial and Inverter price is way lot more.
fruitful things…
Any online shopping stores?
I saw APC UPS on http://www.futurebazaar.com any website for buying batteries?
Thanks for the post. Helpful for people like me.
Great Research… Great explanation….. Great suggestions ….God bless you….
Thanks a lot.
Hello guys,
I am from bangalore.. This is a very informative comments, I need your help guys.
I have decided to but sukam 800va (6200rs) 2yrs warranty and
i am confused which battery should i buy between exide inva500-150AH (30 months warranty) this is a inverter battery life span of 4-5yrs and DOD is upto 1000 cylces
or
exide EL+(60months warranty) this is ups battery life span of 5-7yrs last upto 10yrs and DOD of 1200cycles according to exide in website.
The price difference bet IT and EL+ is 4-5k but i get double the warranty in EL+ with more DOD cycles.
so
1. what is the difference in inverter battery and ups battery.
2. Price IT500 is 11500 and EL+ is 14500rs for 130AH and 17400rs for 150AH. But the spec of EL+ is more impressive than IT500.
3.But my doubt is that do really a battery last 8-10 yrs.
4.when spec compared between EL+ and InvaIT500 EL+ is better and only in one EL+ lags that is Constant limiting current it has 20A and IT500 has 24A so is this very important in battery backup.
SO itself i am confused in buying the battery so can u people clear my doubts and Help me ti inchoosing the right battery.
Thanks Amit for putting in your research results and helping all.
I am considering going in for a 1400 VA inverter keeping in mind future needs.
I assume that I can run it on 1 165 AH battery for now, and purchase the second one later.
Hi Amit,
Thanks for the great info.
I am from Nepal.
Here we have electricity crisis since last 1 year.
Now there is 12hrs/day load shedding. 6hr in morning and 6hr in evening. In March they say it will be 16 hr / day.
Last year I bought Microtek 850 VA inverter + one 150A Exide Inverter plus battery. It used to give 5 hrs backup to run my desktop PC (17″ CRT). But now it only gives 3 hrs backup.
So my question is
1. can I install another battery in parallel connection?
2. If yes will the inverter be able to charge 2 batteries at the same time?
3. If i cannot install 2 batteries in 850 VA (12 V) inverter then will 1400VA inverter (24 V) give like 10 hrs backup for running 1 desktop PC with 19″ LCD
4. How much difference is there between 17″ LCD, 19″ LCD and 17″ CRT monitors?
5. How to calculate time required to fully charge a battery?
Waiting for your reply.
Thanks
Binay
Hi,
I think your calculation to compute AH rating of battery is not correct. You have used 630 Watts, which is the load delivered by inverter. But infact it should be load on battery, which is 787 watts. So x = (787*3)/12 = 196.75 AH.
-Avneet
I am purchasing Sukam 800VA/12A UPS/inverter with battery Exide inverter + 88AH. I want backup of 3-4 hours only with 5tube light only. Will this configuration ( 800VA/12A, 88AH) works OK. What would be the cost of Sukam 800VA/12 UPS and Exide Inverter + battery 88AH?
Pradeep Chandra
+91 9414291406
I have a 800 watts inverter and a 100ah battery, i want to increase the backup time can i add more batteries up to 400ah. pls reply soon
Hello Amit Bhai
great write up with loads of info
i plan to move to my village currently i am living in Mumbai and we dont have any laod shedding or power cuts here
but there in West bengal in summer load shedding is some times 8 hrs adayand in normal days u can expect 3-4 hrs a day
I am a trader in stock market so i need UPS for atleast 6 hrs
for my computer and LCD monitor 1 fan and and a tube light
which UPS / Invertor should i buy to run say 3 fans 3 tube light 1 computer 1 lcd monitor for 6 hrs in a strech and plz mention the capacity ie how much KV invertor / ups should i buy
thanks a lot
Amazing research work done
Hats off to u sir!!!!!!!
And also try and keep the good job goin on
Dude that was a very useful piece of info. Thanks
i am in the process of buying a inverter for home perpose. so pls. guide me & tell me about the rate difference in ups & inverter for same VA. is okaya tubular battery is suitable?
This was a really helpful post. I might just go ahead an buy the same configuration you are using
Ribhu
Hi,
Great Boss, Lot of Tips to buy another Inverter. Actually I have an assembled Inverter which I bought 3 yrs. back. but the burger gave me car battary, n I was not aware of this subject at all. I trusted him, but Now I need to go for another battary, So i am thinking of replacing the Inverter also. I was so confused which one to buy. After reading your tips I will be able to decide better.
Thanx once again.
@Everyone: Thanks for all the comments. I haven’t been able to respond to all primarily because I was a bit busy and a bit lazy too I guess. As an update, my inverter is working pretty well. It has been almost a year now. I am all geared up for the summer.
It has been a while and I have been out of touch as to what latest products are available. I suggest everyone to do a bit of research and get the right product.
dear amith,
i have decided to go for su-kam inverters(folcon / folcon i 800VA), but i need following clarifications from you
1. can i use 80AH or 88AH battery along with 800VA.
2. what is the difference between folcon / folcon i 800 VA.
A M chandraskehkar,
Mysore, Karnataka.
It’s indeed a very simple explanation to questions on home -inverter buying. Well as I want this setup for my village whre we dont have electricity supply So It would be really great help u can prvoide some information on how many solar plates and of what rating we need to charge this 165 AH battery considering six hour sunlight available.
thanks a bunch for the basic/most information. Sitting in US getting quotes for my parents is pretty stressfull as they are varying from 16k to 30k for same configuration. Finally got it down to 16K.
quick note to others asking questions:
1) take him as a guide not a sales man. he can shw the way/wisdom not feed you/sell you the systems.
2) with the knowledge in hand, sales guys can’t bullshit you.
3) get quotes from multiple vendors and let them compete with one another.
happy buying
can you please tell me that is 850 EB same as 800 VA
actually i have bought a microtek inverter which has 800 VA written on it.
and the shopkeeper says it is same as 850 EB..??
Great, useful article. Very helpful, thanks.
Is it true that tubular batteries do not require water top ups at all (or do they need top ups every 3-6 mths?)
Anyone, Please help…
Hi Amit.
Just wanted to say ‘Thanks’ for a highly informative post! Very well researched and informative…
Hi Amit..
Thanks for this great post.!!!
This page is highly informative and very useful.
Cheers.!!!
Thanks your information has helped me to clear my doubts
hi dear amit –realy wonderful job done by u — this matter is a little headache for a non techy person– u have simplified it so well that i was reading till end== congrats to u — dr vaibhav
Hi Amit,
Thanks for the detailed informative post. I have APC HI800SQ 800VA fitted at home. Lost battery during transit from one city to other. I am looking for 150AH for long backup which brand would be the best. Can i go for 165AH with the above APC model. Pls suggest.
Hi Amit,
One stop sloution to my power cut problems. Thanks a lot for a very informative post.
Thanks for sharing the information Amit!. Its very usefull. calculations are explained clearly and it help me a lot to make a decision.
Thanks again!. good job
i want to buy the inverter of 850 va and excide/okaya battery 165 ah. Kindly let me know which brand shall i purchase?
Dear
i require inverter of 850 VA and battery 165 AH. Which brand would be the best and what would be the approx cost for the inverter and the battery. i request for early reply.
well Un doutedly a great Piece of note and informative too. On that analogy I intendto purchase a luminous 800 Va ups with a luminous inverter batteroy.Look forward far such good notes in future as well.
Dear
i require inverter of 850 VA and battery 165 AH. Which brand would be the best and what would be the approx cost for the inverter and the battery
Very informative post Amit. Thank you!
i need to know how much increase will be there on my electricity bill when i install a inverter 800va?
Well hats off to you…..
was gropping in dark for what my exact power requirements are for a long time. This one resolved all that in a flash.
excellent post.
Thanks a lot
Giri
Thanks,
I am impressed with you.
I must caution you that the nominal battery capacity of say 135AH is for 10 or 20 hours discharge rate. Shorter duration will reduce the nominal capacity. For example the data for SF Tube Power 130AH battery gives the following capacities for different discharge rates.
Type 10 5 3 1 (Hours discharge)
6STP130 130 108 93 65
Further the batteries are rated at a certain number of deep-discharge cycle (normally 500 – 1500). There fore it would be prudent to factor this in while calculating the duration for full discharge.
By the way the battery last longer if discharged at a lower rate, hence for maximum battery life it would pay to have a higher capacity battery in the long run.
Excellent guide. Indeed a valuable one. I need your guidance on buying an inverter for my house which should be able to run
1. One 1.6 Tonne AC, 2 tubelights and 1 fan for 3-4 hours.
2. Only one 1.6 tonne AC and 1 tubelight
Great post !!! Been on the net for couple of days looking for answers and your post clarified all my doubts at one shot !!! Thank you.
i’m really impress the way u explain. it solve alot of query of mine.
Thanks Amit for ur informatic posting. keep it up
[...] Re: Which UPS will handle this? Also you need to check whether the UPS has cold-start capability. APC does not have it but their website lists it. I had a APC BackUPS 800RS (800VA) and it didn’t have. My current HP Premium 800 UPS has it. There is a excellent website for choosing an UPS/Inverter. The link is : The Home UPS/Inverter Buying Guide — iLog [...]
what is the cost of EXIDE INVA IT500 ,150AH ,TUBULAR BATTERY IN BHOPAL ?
I NEED IT WITH APC 800 VA INVERTER
i want to have following load during power outage
two fan,one computer and five cfl , pl suggest me
good inverter and battery
Hi Everyone, Thanks for the comments. Unfortunately I am not able to keep pace with the changes! I’ve also lost track of calculations which I did when I bought the inverter. So can’t be of much help now!
Best is to use this guide as a first step and explore further!
hii amit!really this is a good information and knowledge provided by you.I have bought exide invatubular 500 150Ah battery and an inverter of LUMINOUS 800VA for running general household appliances like fan,tubes or CFLs and one desktop also.Is it right choice to buy a LUMINOUS inverter OR Should I go for MICROTEK 800VA OR SU-KAM’s 800VA inverter? WHICH ONE IS BETTER?plz reply me soon.