The biggest you can get without 3-phase power. This fully
online UPS boasts 16KVA of power in a user-maintained, user-installed
design. Configure as 208 or 240 VAC input and output of 120/208/240, no
matter the input.The N+1 redundancy design offers a margin that will maintain
load in the event of failure. The Symmetra is also scalable; adding or
reducing power modules as well as battery modules as the need or budget
may require. Extended runtime frames further expand runtime and scalability.
Buy
APC Symmetra Uninterruptible Power Supplies 
Refurbished
Symmetra LX