Time to buy a UPS (Uninterrupted Power Supply) Suggestions?

[knot]

I use Tripp Lite SmartPro LCD 1000VA UPS ( SMART1000LCD )

 

[Handlobraesing]

TedTheLED, here's my test result:

Load = 325W

APC BackUPS 1000VA modified square wave with 24v 12Ah battery pack:
36min

APC Smart-UPS 1400VA sinewave with 24v 18Ah battery

37min

The battery has 50% more capacity, yet runtime is almost the same!