Historically, electricity consumption has been largely insensitive to short term spot market conditions, requiring the equating of supply and demand to occur almost exclusively through changes in production. Large scale entry of demand response, however, is rapidly changing this paradigm in the electricity market located in the mid-Atlantic region of the US, called PJM. Greater demand side participation in electricity markets is often considered a low cost alternative to generation and an important step towards decreasing the price volatility driven by inelastic demand. Recent experience in PJM, however, indicates that demand response in the form of a peaking product has the potential to increase energy price level and volatility.

Currently, emergency demand response comprises the vast majority of demand side participation in PJM. This is a peaking product dispatched infrequently and only during periods of scarcity when thermal capacity is exhausted. While emergency demand response serves as a cheaper form of peaking resource than gas turbines, it has recently contributed to increases in energy price volatility by setting price at the $1,800/MWh price cap, substantially higher than the marginal cost of most thermal generation. Additionally, the entry of demand response into the PJM capacity market is one of primary drivers for capacity prices declining by over fifty percent. This study investigates the large penetration of emergency demand response in PJM and the implications for the balance between energy and capacity prices and energy price volatility. A novel model is developed that dynamically simulates generation entry and exit over a long term horizon based on endogenously determined energy and capacity prices. The study finds that, while demand response leads to slight reductions in total generation cost, it shifts the bulk of capacity market revenues into the energy market and also vastly increases energy price volatility.

This transition towards an energy only market will send more accurate price signals to consumers as costs are moved out of the crudely assessed capacity charge and into the dynamic energy price. However, the greater volatility will also increase the risk faced by many market participants. The new market paradigm created by demand response will require regulators to balance the importance of sending accurate price signals to consumers against creating market conditions that decrease risk and foster investment.