For a home system, get the most expensive and heaviest UPS that you can
afford from a retail store.
Sorry, Ed, but that's nonsense.
For most people, that would be way overkill, and simply a waste of money.
The purpose of a home UPS is to give you sufficient time to perform an
orderly shutdown in the event of a power failure. It is *not* to let you
continue running for hours while the power is out.
And why should one buy something from a retail store. In almost every case,
it's possible to buy exactly the same product from an on-line source at a
substantial savings over the retail store's price.