3 ms·That is, 100 Wh = 86 kcal. Enough energy to heat 1 kg of water by 86°C (or 86 kg of water by 1°C).by HPsquared 2y agoThat is, 100 Wh = 86 kcal. Enough energy to heat 1 kg of water by 86°C (or 86 kg of water by 1°C).