Provide reliable monitored multi-day backup power at a tower site for under $500

Providing multi-day backup power at all transmitters reduces service calls and improves network reliability significantly.  On many WISP networks, power disruption is the leading cause of client outages.

Most off-the-shelf retail UPS units (eg. APC1100) have very limited run time for their size.  They are designed to provide computers with high wattage, short term power while they are shut down during a power outage.  What a wireless site needs is low wattage, but exceptionally long run times.  In order to obtain monitored long-runtime UPS from vendors like APC, one would have to invest in enterprise UPS products which are typically thousands of dollars and take up significant amounts of space, and will intentionally shut down when operated below freezing.  They are also designed for high wattage applications which raises the cost and space requirements significantly.  Typical tower sites have exceptionally low power draw, but require long run times.  Computer UPS units are simply not designed for this application.

If there is a power failure at a remote location on a Friday night at 10PM it is of great business utility and savings to fix the issue on the following Monday, during business hours.  Often by then, the cause of the outage has been resolved by the power utility or landlord and no site visit with a generator is required.  Also, if there are widespread power outages due to acts of nature, it is not uncommon to have several sites lose power and road access closed by emergency services or impassable roads.  If six sites all lost power, most WISPs do not have enough generator