Question: how much electricity does a 40 gallon hot water heater use?
Answer: Cost to heat water a 40-gallon tank with electricity A 2008 EPA report showed yearly energy use figures as follows: 2195 kWh for a 50-gallon air-based heat pump with a 2.00 energy factor. 4435 kWh for an electric tankless with a 0.99 energy factor. 4622 kWh for a 50-gallon electric tank with a 0.95 energy factor.