Advice on UPS Calculation: Correct UPS sizing for a PA System

Hello Fellow Engineers,

I am having trouble coming up with the correct UPS sizing for a PA System.
Here are the specification.
Amplifier:
Battery power consumption-
Idle - 0.09A , Standby - 0.23A , Max - 13A
Main Power Supply-
Idle - 5w , standby - 13w , Max - 1000w

eg .I have a max loud speaker loading of 400W
i got 2 controllers with each controller consuming 48W.
Now it is fairly easy to just use the max wattage multiply by 1.25 to get the Kva. but however
i also have to take the following details into consideration:

Evacuation time = 1/2 hours
Paging time = 1/2 hours
UPS duration = 2 hours

how do i determine the correct battery capacity and UPS Size?
I thank you all in advance for your help.