N.H. Rev. Stat. Ann. § 72:84

In this subdivision "electric energy storage system" means a facility located behind a retail meter that stores electrical energy that is otherwise produced by an electricity generator or uses electricity to concentrate and store thermal energy, by electrical, chemical, mechanical, or thermal means, for discharge or use at a later time, whether in the form of thermal energy to meet space or process heating or cooling loads or electricity, which can be used to reduce peak loads, compensate for variability in renewable energy production, or provide other grid services, and which does not participate in any wholesale energy markets administered by ISO New England as a registered asset or otherwise. An electric energy storage system shall not include conventional electric resistance or gas domestic hot water heaters.