The Value of Solar Thermal Systems to Supplement Central Gas Water Heating Systems in Florida

Secondary Author(s)

Gu, Lixing; Vieira, Robin

Report Number



Heating; Buildings; Solar Thermal; Solar Energy; Residential


Solar systems save energy and dramatically reduce carbon emissions. Solar thermal systems can be considered the most cost effective renewable energy option available having collector efficiencies reaching seventy percent. A centralized solar thermal system pre heating into a gas-fired water heating appliance has the advantage of generating a great deal of energy. Distributed solar water heating systems are much more cost effective than distributed renewable electric generation options. Economic analysis was performed to evaluate the value of solar thermal systems to supplement central gas water heating systems for three regions in Florida. Revenues from the sale of thermal hot water energy to customers are based on the equivalent and current gas unit (therms) rate pricing. The present value difference between total cost of a central solar thermal system and total revenues were used to evaluate the cost effectiveness of central solar systems. Some of the parameters used in the study include location, rebate programs, multi-dwelling buildings, discount and escalation rates. Gas cost and other charges were provided by the Florida Natural Gas Association. Analysis results indicate that higher overall revenues can be obtained from pilot programs located in central and south Florida, where system costs are lower than North Florida. Central and South Florida systems can protect form freezing without a separate collector fluid and heat exchanger. Since part of the profits depend on rebate programs, a maximum limit imposed on those rebates will discourage applications of large solar thermal systems in large multifamily buildings. The state legislature should re-consider raising the limits or remove the cap. Larger projects offer the advantage of reduced installation cost per energy unit delivered as well as greater likelihood of proper maintenance and should be encouraged by the legislature. The analysis results also show that profits depend on many factors, partially used in the parametric study. These results are dependent on the building water use and system costs used, and a specific analysis should be used for any identified pilot projects during the building design stage. The detailed building simulations combining HVAC system and solar system together are recommended.

Date Published



Heating; Buildings - Residential; Solar Energy; Solar Thermal

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