Is there any reason that a UPS would start to use more electricity over time?

I know nothing about electricity.

We have a CyberPower OL1500RTXL2UN with one expansion module (BP36V60ART2U) delivering power to 4 servers, a storage array and a few switches. Over the course of the past 5 months, the CyberPower has reported a gradual increase in overall power consumption of just over 5kw. We've connected absolutely nothing new to the UPS. 

The batteries are just past 3 years old . . . Replacement is scheduled.