The primary aim of this study was to evaluate if it is possible to detect the energy embedded in a Null electromagnetic wave, which is an electromagnetic wave that does not contain any electric or magnetic fields. In three different proposed experiments describing a production of a Null, or partly Null electromagnetic waves, energy loss in each of the processes was observed which seems as a violation of the energy conservation principle. The "Energy Pair Theory" (EPT) developed and proposed in the article, explains this energy loss. It states that certain energies can be accumulated and stored as "Energy Pairs" that disable each other, and therefore, the energy exists but is untraceable. The Energy Pair Theory puts the concept of Energy in a new and flexible framework that can be further applied and studied. For example, it can provide a possible explanation to the Dark Energy mystery. Other examples examined are the electron positron collision to produce a gamma photon, and the reversed process of a gamma photon producing an electron and a positron. Unexplained issues in these processes are also explained by the EPT theory. This explicit analysis leads also to the unexpected conclusion that electric charge is a form of energy, or in other words the entities of Charge and Energy are equated, as Mass is equated with Energy. This conclusion might also imply that the only distinct entity in Nature is Energy.