Most small UPS Systems use either 12V 7Ah, 9Ah and occasionally 12Ah batteries. In order to determine the runtime you will get with any UPS system find out what batteries it contains, enter the power consumption of your load, select the number and type of batteries and a good guess will be calculated.
Advanced features include the ability to adjust UPS efficiency, and also add in residual UPS power requirement.
You can select the precise model for most of the systems here on UPSMart using the drop down selector.