Despite the high upfront financial costs associated with the existing technologies for energy storage they have become more appealing in recent years in response to the increasing importance of non-dispatchable sources of generation in the energy systems of developed countries. One of the essential pieces of information required to value the monetary benefits which can be achieved when investing in energy storage is the price that energy will command when it is released, compared with the price paid when injected into the storage. In this paper we investigate this relationship using time series statistical techniques for various maturities of forward prices, using data on assessments of power prices for future delivery. We will examine the relationship for predictability and size of gap in order to answer questions about the likely financial benefits which can be obtained from optimal time management of storage facilities, using a technology neutral approach. Our initial results indicate that such arbitrage opportunities exist for storage facilities, especially when energy is stored over a short- term period of a day or a week.