Solar Thermal Water and Space Heating

The sun’s energy can be directly used to heat both water and space in buildings and homes. Heating domestic or commercial hot water is generally the first goal of a solar thermal system, and space heating is a secondary consideration. The design of solar thermal systems is generally quite simple; solar energy is collected to heat a fluid.

There are numerous types of solar thermal collectors, ranging in complexity and efficiency. Most systems in Wyoming are indirect (a heat transfer fluid, as opposed to domestic water, is heated in the collectors and then circulated to a liquid-to-liquid heat exchanger where solar heat is transferred from the solar fluid to the domestic water), active (pumps are used to circulate the fluid, as opposed to convection), or closed-loop systems (a solar fluid remains within a single circuit at all times. Closed loop systems are indirect systems because the sun heats a solar fluid, such as a water propylene glycol solution; this fluid then transfers heat to domestic water). The most common systems in Wyoming are:

  1. Flat plat collectors
  2. Evacuated Tube collectors

The Department of Energy (DOE) provides an excellent overview of the types of solar water heaters.

Milt Geiger, Former UW Energy Extension Coordinator, goes through the basics of two energy efficient options for homeowners – Solar Thermal to heat water and Geothermal Heat Pumps to heat and cool air.

Frequently Asked Questions:

  1. How can I determine if solar thermal is right for me?
    A solar thermal array may make sense for you based on the reasons discussed in our Energy Basics web page. Financially, thermal energy from the sun makes the most financial sense if:

    • You need to replace your hot water equipment in the near future;
    • You heat your water or home/business with an expensive fuel source, such as propane or electricity;
    • You are uniquely positioned to utilize incentives, such as a rural small business that uses 125+ gallons of water per day.
    • If you meet one of these broad criteria, you can learn more about the feasibility of solar thermal from the DOE Solar Water Heating web page.
  2. What are the principle advantages and drawbacks of solar thermal?

    1. Cost Effective – With an excellent resource, generous federal incentives, and many buildings heating water with expensive fuels, solar thermal can be a cost effective investment in Wyoming.
    2. Reliable performance –Solar thermal has come a long way from the often unsightly and unreliable systems of the late 1970’s and early 1980’s.
    3. Easy to integrate – Solar thermal systems are relatively easy to tie into existing hot water or heating systems.


    1. High upfront cost – The systems can be cost effective over time, but the installation cost is up to 10x the cost of similar electric hot water heaters.
    2. Need for unobstructed southern exposure – Solar panels require unobstructed (no shade) from 9AM to 3PM southern sun. The low sun angles in winter months can sometimes make this challenging in residential neighborhoods.
    3. Need for a backup –Unless you are willing to take a cold shower on a cloudy February day, solar thermal systems require back systems to ensure hot water remains available.
  3. What are the incentives?
    Solar thermal is eligible for significant federal tax credit and grants. Utilities also often offer rebates. No state incentives currently exist. Please visit our Incentives web page for additional information.
  4. How much does a solar thermal array cost?
    Solar thermal costs can vary, but generally a 120 gallon system (enough hot water for 4-6 people) will cost $7,000-10,000.
  5. Where can I find a Wyoming-based contractor?
    Please see our ever-expanding list of Wyoming-based contractors


Wyoming Renewables: Resources