The amount of heat generated during thermal runaway in lithium-ion cells is dependent on the failure mechanism and abuse method. This study determines the heats generated inside and outside a 64 Ah lithium-ion pouch cell when it is forced into thermal runaway by nail penetration, heating, or overcharging. The generated heats were determined by battery calorimetry, jet flame calorimetry, and oxygen depletion calorimetry. The ratio between heat generated inside or outside the cell is found to be dependent on the abuse method. The overcharge experiment was most severe with respect to heat generated outside the cell, with 89% more thermal energy measured by the jet flame calorimeter compared to nail penetration. For heat generated inside the cell it was opposite, where nail penetration was the most severe with 53% more thermal heat generated compared to overcharge. We explain these differences from the cell mass losses during thermal runaway. When the cell mass loss increases, the heat generated outside the cell increases and simultaneously the internal heat generation decreases. For the safety of a battery module, these results imply that the possibility for propagation of a thermal runaway between cells is dependent on failure mechanism.