Longer Run Time on lower rated models?

[Anonymous user]

Wondering if someone can explain how a slightly higher rated UPS model has a lower run time capability vs. a lower rated model. Tried asking a couple of my peers but none of them seemed to know.

[APC Smart-UPS - SUA5000R5TXFMR|http://www.apc.com/resource/include/techspec_index.cfm?base_sku=SUA5000R5TXFMR]
4000 Watts / 5000 VA
Battery VAh Capacity: 816

[APC Smart-UPS RT - SURT6KRMXL3U-TF5|http://www.apc.com/products/resource/include/techspec_index.cfm?base_sku=SURT6KRMXL3U%2DTF5]
4200 Watts / 6000 VA
Battery VAh Capacity: 960

Say we use 1kW/1.4kVA as an example. According to the run-time charts:

SUA5000R5TXFMR - 1hr 3min
SURT6KRMXL3U-TF5 - 39min

Pretty big difference of ~62%. If I recall, online UPS units are usually less efficient but a difference of ~62%!? Seems like something's off to me. Guessing the answer probably is something obvious but can't seem to figure it out here. 🙂

[upsguy_apc · Accepted solution]

The SUA5000R5TXFMR has a larger battery. If you look in the manual for the UPS it has 108lbs of batteries (4 batts 27lbs each). The SURT6KRMXL3U-TF5 has a 74lb battery(both batt packs =74lbs). So in terms of back up time with UPS lead = run time. The SUA 5000 has more lead paired with a slightly lower amount of output power and you get your large diffrence in stated run time.

Hope this answers your question.