Comparing costs to heat hot water

Adding up electricity, gas and propane, most (probably half to two-thirds) of the energy you use in your house is for heating, ventilation and air conditioning. One of the most significant other uses is water heating.

In most homes, the same hot-water source is used for bathing, dishwashing and laundry. To compare water heaters, I looked up the specifications for similar, popular water heaters at one of the big-box stores. The propane water heater requires about 0.267 gallons of propane per hour. The natural gas water heater requires about 0.209 therms of gas per hour. The electric water heate...