An aging population that depends more and more on air conditioning and medical equipment, increased use of electronics requiring uninterrupted power, and increased concerns about the reliability of grid-supplied power have all contributed to a growing demand for home emergency power systems. Grid transmission congestion led to a five-fold increase in electricity purchasing transactions that could not be completed between 1998 and 2002.1 Also, electric grid capacity margins have decreased significantly over the past twenty years, increasing the risk of an outage. These margins are expected to decrease further over the next decade, from around 20% to 10%²