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
Thanks a LOT Amit…..This is really an awesome guide for buying an Inverter/UPS. After reading this material I have purchased Si-Kam Falcon-i (800VA) home UPS @Rs 4600/- along with Exide Lead Acid 1500 AH battery @Rs 8100.
Thanks a LOT Amit…..This is really an awesome guide for buying an Inverter/UPS. After reading this material I have purchased Su-Kam Falcon (800VA) home UPS @Rs 4600/- along with Exide Lead Acid 1500 AH battery @Rs 7900/-. I did not purchased the tubular battery as there was not much need for the same as power cuts are very rare in our area with maximum half an hour of cut.
Difference between Su-Kam Falcon (800VA) & Su-Kam Falcon-i (800VA) is of warrenty only. Su-Kam Falcon (800VA) has 2 years warrenty whereas Su-Kam Falcon-i (800VA) has only 1 year warrenty.
Su-Kam Falcon-i2 (800VA) has graphical display.
Hi Amit,
if anyone asks me for Excellent and outstanding job , I would refer him to you.Bro, I am thankful to you as your information and suggestion has helped me to buy two home inverters.
Only one question – if any problem with LCD monitor may happen, when it is connected to Sucam – falcon 800 VA sine wave inverter. Actually at my home the power cable of LCD monitor got damaged (entirely plug to monitor got melted and blown) twice in a row, I am a bit afraid thats why asking you…..Please Help
Hi! anybody please help me.me not having a seperate UPS wiring..and getting one now is very cumbersome and destroys the aesthetics.my need is just to run 2 tubelights for an hour or two.i am looking at portable inverters.can i take computer UPS for this purpose?please throw light on these topics..
Hi Everyone, thanks for the comments.
@ Vikas: Both Luminous and Microtek are good I guess.
@ Abhi: Your LCD power plug got damaged when the power was on inverter or or mains? I have been using LCD screens and monitors without any issue. Get your wiring checked. Also as a precaution, use Spike guard for electronic equipments so that the fuse blows up in case of high voltage etc.
@Suman: You don’t really need to get a complete wiring done. Just get a good electrician and ask him to connect to the main MCB to the preferred points. Only thing is you may not have a choice of exact points which will be on backup. SO you might need to switch off a few appliances when power goes off, else the inverter will shut off on high load.
Hi Amit,
Excellent post !! Wish I discovered it earlier before my purchase. But, fortunately I purchased similar combination of Sukam Falcon-i 800 VA and Exide Invatubular IT 500.
Since u have been using the equipment longer than myself, I just want to ask something about the performance.
1. I have noticed a slight voltage drop during power cuts. For eg, the tubelights (copper ballast) goes off and then turns on. Similarly, the fan speed also slows down a bit, though TV/Laptop runs uninterrupted.
2. There is an occassional humming sound when exhaust fan runs on inverter.
3. Within a month of purchase the glass fuse had blown, now m using the spare one. Pls note: there was no additional load when that happened.
4. Of late there is a bit of topping on 1 of the nozzles of the battery, though there is no indication of refilling as yet.
Due you think the equipment is running alright ?? Have u faced any of these situations??
Thanks in advance….
[...] Re: Need new UPS Have you checked the prices of SuKam Inverter/Home UPS ? I think they are priced, without batteries, within Rs 4500-6500 (depends on your location/city/state). (Example: In Bangalore it is around Rs 6500 whereas in Mumbai it is around Rs 4500. ) If you need to calculate the consumption to select a appropriate VA UPS, here is a link: The Home UPS/Inverter Buying Guide — iLog [...]
Hi Guys, yesterday got an inverter installed after doing much research.
Su-Kam Falcon Rs.7000
Exide InvaQueen 135 mAh Rs.9000
Installation 500.
Working pretty fine, an the guys were good to respond. the wide difference in the price is mysterious. By the way, is the mild hissing noise frm the inverter is normal?
[...] Re: Need inverter suggestion For checking the required rating for UPS/Inverter rating, please visit this website: The Home UPS/Inverter Buying Guide — iLog [...]
@ Dr. Prasanna
My purchase of Falcon was at Rs. 4800, IT 500 at Rs. 10,600. (guess 3 months back). So the difference is indeed mysterious.
The mild hissing sound could be because of a small smps like fan running inside. You can feel it if you place your hand near the rear side. Otherwise it is supposed to be a quiet creature.
regards…
i have appreciated your posts. thanx. one question. what is the maximum no of batteries i should connect on an EB1400 inverteter i already have 2pairs of 12v connected ie 24v from 2 pairs of batteries can i add in parallel another pair , what are the repurcussions?
Hi!
Kudos to you for a really well put together piece demystifying domestic inverters and batteries. Really found it useful. Thanks a ton!
Sosha
please tell me what is the difference between LONG BACK UP UPS(HYUNDAI) and SINE WAVE UPS(HYUNDAI)?
Hi Amit,
Recently I have bought an inverter(SUKAM – 850 VA) and Exide tubular battery(150Ah) after seeing your article and lot of comments. Can u please tell me whether I can connect my computer directly to the inverter power supply without ups, since my UPS is not working and instead of buying new UPS.
Hi Amit,
first of all congrats your ups buying guide article was more useful informative.I have lot of question in deciding inverter and battery back up time but your resolves all my query . thanks a lot
rgds,
nivash.k
Pls Let me know the total AH rating anumber of batteries required (100 ah smf) for online UPS 30 KVA with 4 hours back up
calculation of ah rating for 4 hours 30 kva online ups
hi,
does the VA of an inverter determine the time required to recharge the batteries? Is 800VA inverter enough to recharge two batteries of 180AH and 150 AH each? power cut offs in my area reaches sometimes to 15 to 20 hours a day!!!!!
Hi,
I have a APC 800 VA inverter. Currently, the power backup is not working for more than 15 mins. The Inverter gets switched off. After checking with the Battery people, they said, we need to change the battery, as its more than 3 years old.
Can you please guide me, which 100AH battery should I buy. Some of the battery shop says, buy Exide battery which costs 5,500 RS and some of them says, buy SF Sonic battery, which costs 5000Rs.
I patiently read about 30% of the review and the complete article. I feel I am clear and I am intending to venture for parkarpower inverter and battery since I am told that it would be comfortable to go for both from the same manufacturer for some calculated advantage. Hope that come true.
I live in ggn and have frequent too many power cuts I have sukam 800va invertor with 165 AH sukam battery but the backup is not sufficent. I am planning to buy a invertor assuming we have continous powercut of 10 hrs and we have load of 1 TV plus 2 tubelight 2 Fan & 1 CFL
what is the size of invertor I have to buy ?
Invertor guys mentions I need 1400 VA invertor Sukam model smiley and 2 batteries of 150 AH and sell old 165 AH battery & 800 VA Invertor
please advice how to plan it and which battery and invertor to buy make & model & Wattage
Thank you,
May God bless you.
You made the difference,
hats off. You have very good writing and analytical skills
Keep sharing …
cheers
Anil
thanks for the guide lines great job
Great man and thanks a lot. Yours is the bet guide to buy an inverter even today.
an xcellent post…very informative..
Recently I bought 800VA SineWave luminus Inverter powered with Exide 180A Battery. The problem with my Inveter is that, while I turned ON my Sony 21″ CRT TV, it goes OFF with overload sign on Inverter, but once I reset the Inverter TV will turn ON. For information there were no other load except one tube was running. Twice I have changed Inverter (Luminus with same rating), but problem remain same.
Would you please suggest me whether shall I go for another brand Inverter?
Thanks
R. Tandukar
Thank You,
I went thro a lot of writeups of UPS and their dealers sales gig the last 2 weeks but your explanation nailed it best !!
It is a unique way to calculate the required inverter and battery.
I have a question, I have “Su-Kam Falcon-i (800VA) Sine Wave Inverter” , now I want to purchase battery,
I want power backup for -
* 2 PC (P4 computer with 19″ LCD)
* 1 Fan
* 1 CFL
the problem is with battery, I have 2 options.
1. If I purchase “Exide Inva Tubular IT 550 (165 AH)”
then
a) how many hours back-up I will get for all these (2
PC,1 Fan, 1CFL)?
b) how many hours it will take to re-charge the fully
used battery?
c) How much it will cost (approx.)?
2. If I purchsed “SF Sonic Power Box (150 AH) 12 V”
then
a) how many hours back-up I will get for all these (2
PC,1 Fan, 1CFL)?
b) how many hours it will take to re-charge the fully
used battery?
c) How much it will cost (approx.)?
Please inform me immidietly, I am waiting for your reply.
Thanks a lot for all the great information.
Too good…. Calculations and justifications really superb…
This will fit for lot of people who are looking for Home UPS…
Thanks a lot dude.
Thanks buddy ! it is really useful for me.
9810775185
Gr8 research. Thanks for all the information.
Hey Amit,
Just wanna to Say, Thanks buddy ,It’s really help me to understand the in-depth of the topics.You really awesome..the way u simplified the topic ..Keep it up .
Hi , i wanted to know can we run a small 0.8 ton ac on 1600 va inverter+ 2 X180 ah battery
dude its ample of information to know the specifications of the inverter and batteries which is suitable for my requirements…thank u dude…
Amit,
Really the best post (buying guide) anybody can find on net if he is really considering buying Inverter.
I am about to buy one which can make you understand why I reach on your post. If you still have any touch or time for it, have you ever compare difference between Sukam and Luminous as loads of people on net have so many different opinion about them that its hard to believe which one is better?
Cheers
Alok
Its like the best post ever man, I don’t know.
Y’ore a champ and stuff man!
Thanks Amit, Your info was very useful to me for buying an UPS. I like your approach!
Can u plz suggest me the minimum VA inverter & min AH bateriers available in market? Supose I have requirement of = 2 fans, 2 tube lights, 1 TV. So its around = appx 350watts. & with P.F. its around =440 VA. & i need battery backup for only 2 hrs. Therefore bat. required= appx 75AH. So is this ratings ie 440VA(Inv) & 75AH(Battery) are available in market?
Hi Mohit!!! I am giving some information, i hope it will be usefull for U..
For Ur requirement U can go for 600 A-h Full sine wave sukam or Luminous inverter with exide battery of around 99 a-h which is available in the market.
it will cost you around 3600 + 6000 == 10000 INR
Great article.
I’ll bookmark it share it when ever anyone i know plans on buying inverter.
Suggestion : You should submit this page to google search search optimization.
I bought a microtek850 va Sine Wave inverter and Exide IT 500 150AH battery on 16th April, 2010. It should give power for 650-680W load, but when I connect 3 fans & 5+1 tube lights it shows overload. I think the inverter or battery is faulty. What should I do now, plz, give your suggetion.
enough explanation for common people. great work. thanks
I am looking for an inverter-My requirement is 3 Fans.4 CFL, 1 TV(29′ Inches),1 Laptop and one PC with 17′ Flat Monitor- Can i go for 800 VA..?or need 1KVA..? Is AMCO 180 AH battery is sufficient for 4 hrs. backup..?- Looking for your input..
really excellent post dude but plz help me about some doubts i bought an inverter with 850 EB written on it does it mean 850 VA also i want to know if i can run a desi cooler with an exhaust motor of rating 180/400W and 12 W cooler pump and also for how long
Great post. Thanks. I have asked so many people about this calculation and hardly got a convincing explanation.
hello…how is ur sukam invertor doing ….?????
plz reply
I already have 600 VA ups for my PC which gives me good backup
but now I need around 3hrs backup for my pc.
I also need 2 lights nd 2 fans.
Please tell which inverter to buy from sukam Pure Sine Wave model no. or shall I buy some other brand ????
Also do I need to buy home ups inverters or a normal one since I already have ups for PC ?
thx
hi…
I m shashi 4m Bangalore , Can i use Exide MHD 1000 for my 800VA Inverter?
Dear sir,
I do have a APC hi800sq inverter with 100ah battery, the battery is completely drained out now & hence wants to upgrade it with 150 or 180 ah tubular battery.
will the inverter charge it properly?
pls suggest
I very much confused to select best option in my home ups system.After seeing this i got a great idea to tackle this problem.I clear about backup times too.I extremely thanks for your guidance .Your helping mind is great,you are bless by all who get benefit from this.