How to calculate delta energy?

Delta energy is calculated differently depending on whether you mean physics, chemistry, or general energy change, but the core formula is always final energy minus initial energy. In general science, delta E or ΔE = E final - E initial. If the result is positive, energy was gained. If negative, energy was lost. In chemistry, delta energy often refers to change in internal energy, enthalpy, or Gibbs free energy. For enthalpy, ΔH = H products - H reactants, or ΔH = Σ bond energies broken - Σ bond energies formed. You can also calculate ΔH using standard heats of formation. For Gibbs free energy, ΔG = ΔH - TΔS, where T is temperature in Kelvin and ΔS is change in entropy. In physics, change in kinetic energy is calculated as ΔKE = 0.5 * m * v final squared - 0.5 * m * v initial squared. Change in potential energy is ΔPE = m * g * Δh. In electricity, delta energy is power times time, ΔE = P * Δt. In quantum physics, delta energy for a photon is ΔE = h * f, where h is Planck's constant and f is frequency. So first identify what type of energy change you need, find initial and final states, and subtract. For chemical reactions, use a table of standard enthalpies and entropies.