Electric power systems are traditionally designed and developed with the assumption that demand is exogenous to the system.  Connecting the feedbacks from the system to consumers will provide incentives for consumers to reduce demand during periods of high system prices.  A system dynamics model is used to analyze the dynamics and long term implications of adoption of technology to enable demand response.  The model includes the decision by consumers to adopt demand response technology along with decisions by investors to build generation capacity.  The adoption process reduces overall system prices for peak demand periods, creating feedbacks with generation investment.  The effects of technology improvement via learning, long term demand elasticity, and policies to promote adoption are considered.  The results of the simulations show that diminishing returns to adopters and significant externalities in terms of free rider effects limit the attraction of individual adoption.  A subsidy to alleviate the costs to individuals can be justified by the significant system level savings from widespread adoption.  Several pernicious effects can emerge from large scale demand response, however, including increased price volatility due to a reduction in generation capacity reserve margin, an increase in long term demand, and increased emissions from the substitution of coal plants for natural gas and renewable generation capacity.