Question: how much electricity does a 40 gallon electric water heater use?
Answer: Cost to heat water a 40-gallon tank with electricity Annual consumption is figured in therms as 41,045 Btu/EF x 365/100,000, or 149.8 therms at 100% efficiency. 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.