Solar Water Heating Energy Self Assessment
The solar water heating calculator estimates the equipment requirements to meet 50 percent of your hot water energy usage. Reducing your hot water needs before you consider a solar water heating system will reduce the size and cost of the system needed. Installing high efficiency water heaters, insulating hot water pipes whenever possible, repair leaking pipes and taps, and turning down the temperature on hot water heaters will reduce energy needs for heating water.
The most economical way to use solar thermal energy is for preheating water before it enters a water heater rather than 100% replacement. Preheating results in less energy used by the current water heater. The calculator estimates the surface area of solar thermal panels required to preheat the water to replace 50% of your water heating energy use. The calculator evaluates thermal energy use based on user input. This tool does not provide a site-specific renewable energy assessment. If after using this tool, you want to take the next step, contact a certified solar site assessor to do an evaluation of your specific location. Trees, buildings and terrain can affect the amount of solar energy that can be collected.
Frequently Asked Questions:
Solar energy from the sun is collected by solar collection panels and transferred to a heat transfer fluid circulating through tubes in the panels. The fluid, typically an antifreeze, transfers the heat to water in a heat exchanger. The warmed water is stored in a water tank and is used as preheated supply water for a water heater. The level of preheating will depend on the type of collection system used, climate conditions (temperature, solar radiation) and the exposure of the solar collection panels to direct sunlight. Solar collection panels used for water heating are different from those used to produce solar electricity.
Solar collectors collect the sun’s energy which is transferred to a fluid, typically a glycol solution, which runs through a piping system in the collector. In areas where freezing temperatures seldom occur, water can be heated directly which eliminates a heat exchanger. If freezing weather is forecasted the water is drained out of the collectors hence the name “Drain Down System”. Flat-plate collectors are the most common but evacuated tube solar collectors are the best option for high temperature or high volume applications such as a car wash.
Heated fluid circulates between the storage tank and the collector(s) by natural convection (thermo siphon) or mechanically pumped systems. In an indirect circulation system, a glycol antifreeze solution is circulated between the solar panels and a heat exchanger where the heat from the antifreeze is transferred to water. These systems are used in cold climates with long periods of freezing weather. In a direct heated system, water is used as the heat transfer fluid and circulated directly to the solar panels from a storage tank.
Pre-heated water from the storage tank flows into the water heating unit as hot water exits the water heater for use. A solar water heating system requires a conventional water heater to heat water that didn’t reach the desired set point due to lack of solar energy.
A controller manages water temperature and actuates the circulating pump when solar energy is heating water in the solar panels.
An additional system cost is an insulated storage tank for preheated water which is often sized at the same volume as the water heater. A rule of thumb used for active solar water heaters is that 1.5 gallons of storage are required for each square foot of solar collector.
|Federal tax incentive (% of installed cost)|
|Non-profit / Government owned||Not eligible|
Visit www.energystar.gov to find more information about the federal tax credit currently available for solar systems. The federal tax credit amount is automatically calculated in the assessment tool.
Many state and utility programs are available to fund solar energy projects. Contact your utility company or visit www.dsireusa.org for possible state incentives available for your solar water heating project.
Step 2. Educate yourself. It is important to understand how a solar water heating system operates, and how to manage the system.
Step 3. Investigate the type of permitting required in your local area. Your site may be located in an area with a homeowners association or township laws which govern solar panel installation. Be aware of any building permits that may be required for installation.
Step 4. Determine the availability of tax and grant assistance programs, including their application and payment processes. Some incentive programs may require paperwork or other steps to take before the system is purchased or installed.
Step 5. Get a site assessment - Consult a professional solar thermal installer to estimate the potential for solar water heating at your business, farm or residence. A certified solar professional can be found at the National American Board of Certified Energy Practitioners.
Step 6. Get quotations from two or three companies. Compare quotes to ensure they are quoting similar size and type of equipment. Ask questions.
Step 7. Consult with your tax preparer to ensure that you can take advantage of any state and federal tax credit available.
Step 8. Check with your insurance carrier to see if your proposed solar system is insurable.
Step 9. Order the system to be installed by a professional solar thermal installer.
Step 10. Once the system is installed, complete all applicable grant or tax incentive forms.