I sold/serviced UPSs from 350VA (breadbox size) to 1.5MVA (two stories tall).

The biggest enemy of the smaller units is heat/thermal design. Compact case designs do not allow for proper cooling for longest battery life or the inverter's cooling. The battery is usually very close to the warm/hot charger/inverter circuitry. Matters worsen when you consider house air conditioning fails during a warm weather outage and there is little/no air movement, to boot.

Installing a small cooling fan on the UPS output and opening up the case cooling ports will help. It is entirely possible for a 350VA UPS to run on a larger battery for extended periods as long as it is cooled adequately. The cooling is a challenge, tho, especially in true "lights out" conditions.

I, too, am looking at a solar/battery setup.


-josh