For the National Rural Electric Cooperative Association, Natural Resources Defense Council, and Peak Load Management Alliance, Brattle experts evaluated the economic benefits of controllable electric hot water heaters and heat pump water heaters in participating in the wholesale power markets.  We evaluated a range of water heater control strategies, including peak shave, energy arbitrage, and fast-response to provide frequency regulation.  Our analysis quantified the system benefits, potential revenues, and carbon emission effects in PJM and MISO under both existing and projected future market conditions.