Development of photochromic molecules for solar energy storage has two major challenges: (i) to store a sufficient amount of energy in the metastable isomer and (ii) to control the energy-releasing step, i.e., setting it on hold until the energy is needed. Combining the dihydroazulene/vinylheptafulvene (DHA/VHF) photo-/thermoswitch with the dithienylethene/dihydrothienobenzothiophene (DTE/DHB) photoswitch could potentially meet these challenges. The combined multimode switch is studied by density functional theory in order to predict its energy storage properties and spectral behavior in various solvents before discussing its suitability for use in solar heat batteries. An energy storage capacity of 0.17 MJ/kg is calculated which corresponds to a specific energy of 46 Wh/kg—slightly larger than that of a common lead–acid car battery (∼40 Wh/kg) but still only one-fourth of lithium-ion batteries (100–250 Wh/kg). The usual trend for 1,8a-dihydroazulene-1,1-dicarbonitrile and its derivatives is for their energy storage capacities to decrease dramatically as the solvent polarity is increased, but it is found that solvent effects are not as significant for the combined DHA–DTE system. Furthermore, the spectral data indeed imply a possibility of controlling the back-reaction from the energy-rich metastable isomer by light stimulus, thus enabling one to release the stored energy upon request. This work thereby represents important progress toward efficient long-time solar energy storage in photochromic closed-cycle molecular systems