WTB Sinewave UPS Inverter, so need suggestions.

I was a happy man till the Friday powercut recently started again. and now due to covid power cut problems are increasing as fixing takes time for the power company.
so decided to pull the trigger and get a Sinewave UPS Inverter. Now The requirement are as below:
1) 3 x fans.
2) 3 x 15w bulbs.
3) My Battle Station (1000watt smps) with 2 x 2k monitor.
4) My Secondary System (750wattt currently or 850watt in future) with 4x 1080p monitors.
5) Wifi router.

Backup required : min 8hrs and max 12hrs backup.
Got a quote of a 4kva Sinewave UPS Inverter with 4 x 150mAh Excit batteries costing around 80K.
Will this do or I should go for a 5 / 5.5kva Sinewave UPS Inverter.
also if things go out of budget, can get half battery now and half next month and have no issue ? i.e. for e.g 2 batteries now and 2 next month also no looking for a solar solution as I say in a rented flat, in future solar definately so this can also be used with that setup, right ?

nithishsabapathi said:

Check out LiFePo4 battery based solutions.

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are those solar battery special ? currently I will not be installing solar for next 2 years or so. so will it work in normal setup ?

nithishsabapathi said:

These batteries will work in a normal setup too, but would require a special inverter though. If these batteries suit your budget, you can definitely go on with them because these have around 2000 charge cycles and also very safe and smaller in size compared to the Lithium-Ion and Lead-Acid batteries.

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Any specific model which you can suggest to me for the battery and inverter ?