A solar hot water system with a propane tankless water heater backup yields the lowest annual energy costs for homeowners, according to a recent study of 11 types of water-heating systems.Tom Jaenickeof the Propane Education & Research Council presented the study’s findings Oct. 28 during the Plumbing-Heating-Cooling Contractors – National Association’s convention in Las Vegas.

The research, conducted for PERC in 10 geographic locations, states the solar/propane system averages about $150 annually in a typical U.S. home. The system with the next lowest annual energy costs is the propane condensing tankless unit at $240 on average, which costs slightly less than the heat pump water heater at $246.

At the other end of the spectrum, a standard-efficiency electric storage tank is the system with the highest energy costs, averaging $447 per year.

 A critical point, according to the research, is that the Energy Factor rating for a water heater is not useful on its own when comparing the annual energy costs of systems with different fuel sources. For example, the standard-efficiency propane storage system with EF 0.59 has lower annual energy costs than the high-efficiency electric storage tank with EF 0.93 and the electric tankless system with EF 0.99. 

The study, “Energy, Environmental and Economic Analysis of Residential Water Heating Systems,” also looks at carbon dioxide emissions, installation requirements and annual energy costs at the regional level. The Northeast is notable, with higher electric rates driving electric storage systems above $600 per year. Energy costs for fuel-oil-fired water heaters in this region average $381, while the propane noncondensing tankless is $363 and the propane high-efficiency storage (noncondensing) system is $438.

More information can be found atwww.buildwithpropane.com.