You could look online for a refurb at a lot lower price. I've setup such systems and generators for a number of people. Years ago I found a junk dealer who had a perfectly good 10 kw ups that came out of a hotel, his crew got hold of it and ruined the darn thing. It used a dozen or so lead acid batteries about the size of a standard car battery. There are companies all over that sell refurbished and good used equipment. I have several used APC rack mount units in the shop that were picked up at auction. I haven't messed with the things yet because the price of batteries went out of sight a while back. Here's a link to one company:
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TDD