The rising costs associated with power supply anomalies are causing a surge in demand from commercial and industrial businesses for modular energy storage systems capable of carrying large loads or even whole facilities through brief power sags or outages. This report assesses a host of new products and services vying for a share of the market, including low- and high-speed flywheels, improved chemical batteries, superconducting magnetic energy storage, and ultracapacitors, as well as new systems that incorporate several of these devices or even combine them with distributed generation technologies. (PQ-3; May 1999; 56 pages)