Its not for the save data its more because it happens 5 6 times a day in my country so my PS3 could not hold it so it isnt much for the data its more so that it wont damage itself.
Let me state something in my house theres a backup for when the power goes away (and a generator but we rarely turn it on) and when the power goes out my tv refrigarator lamps fans and a few other things dont turn off when the power goes out.
P.S I understand your confusion but i only want a UPS that can hold my PS3 when playing UNCHARTED2