Thanks for supportive review of the thread.
1 ton AC takes 9 Amps at starting and then within a minute or two becomes stable at 6.5 to 7 amps. Multiply Amps with Voltage (220) and you'll get the wattage
I.e., 9 amps x 220 v = 1980 Watts and 7 amps x 220 v = 1540 Watts.
It means that your AC will consume almost 2000 Watts at starting and 1500 Watts on continuous running. 2000 Watt is the key figure here as without it the AC compressor won't start. While selecting a genset, keep in mind that your total load should not exceed more than 80% of the generators total capacity. In your case, you should search for a generator with an output rating of minimum 2400 Watt (2.4 KW) or divide 2400Watt with 0.8 Power Factor 2400/0.8=3000 VA or 3 KVA.
Don't mix KW with KVA. KVA is always larger than KW.
You need 2.4 KW or 3 KVA genset.
My suggestion...........calculate the load of your UPS too and put it on Generator cause WAPDA will be absent for long time and your UPS won't be able to charge........Secondly, when a generator is running than why not to take advantage of it and also charge UPS?
Now about the brand part........I consider Generator as an investment, just like a car. It gives you services and comfort. So its better to invest in something worthwhile rather in some Chinese crap that will require your service instead of giving service....Lolz.
Honda is the best of the best in the market and also my personal experience. They are expensive but trust me every penny worth it.
Here is a link of my Honda and you'll get a better idea after reading the discussions there.
www.pakwheels.com/forums/sale/209979-fs-honda-made-japan-gas-generator-em6000gn-free-ats
Second option is Yamaha, if you can find a genuine one. Both of these are Japan made, expensive but trouble free. All you'll be doing with these is oil change and air filter clean and that's all. They are designed to run for years and years.
Third option is Chinese. They are cheap (one forth the price) but will keep on bothering you.
Hope I explained enough.