Residential and commercial water heating in the United States consumed nearly 3,700 trillion British Thermal Units (BTUs) of primary energy in 2010. Nearly half of this primary energy was lost as waste heat at the point of power generation to provide electricity for electric water heaters. In the residential sector alone, water heating accounted for 17% of total 2010 on-site energy, use or about 1,960 trillion BTUs. Of this amount, about 22%, or 440 trillion BTUs, was consumed by residential electric water heaters. However, 1,380 trillion BTUs of primary energy was required to produce this retail electric power at the power station, indicating that electricity generation is much less efficient than directly burning fuels for water heating.
This study analyzes 2010 baseline primary energy consumption for water heating in the US by considering energy conversions and end-use efficiencies in the residential and commercial sectors. In order to assess more energy and carbon-efficient means of heating water, we defined four additional scenarios in order to quantify potential energy savings by replacing electric water heaters with more efficient, commercially available technologies. The scenarios ranged in scope and technology deployment, and resulted in energy savings of 10–25% and carbon dioxide emission reductions of 10–20%. Although future deployment of water heating technologies is not likely to replicate any specific scenario, the conclusions drawn from this study are useful in guiding policy incentives and consumer behavior in regards to choosing between water heating technologies.