Depends on what you have hooked up to the upc. If you just have a circulation pump hooked up it would last a while. I had my return pump and circulation pumps and the heater hooked to it. Would last about an hour for me. 100 gallon display.
heaters will drain an UPS fairly quickly. I dedicate my 2 APC units to powerheads and APEX AUX P/S only.

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