The California Solar Initiative – Thermal Program is scheduled to sunset on July 31, 2020. At that time, no new residential, commercial or multifamily applications will be accepted. For questions about the incentive or application deadline, we encourage you to contact CSE’s solar thermal team via email.

Solar Water Heating for Contractors

The California Solar Initiative–Thermal Program is no longer accepting new incentive applications. If you are a contractor or property owner with a project in review or due payment, refer to the Active Applicants page.

Contact Us

CSE will continue to support CSI-Thermal applicants during the sunset period. For any questions related to the program or solar water heating, contact us at

Selected Resources

CSE does not endorse any particular program or organization, but offers these links to resources we find particularly useful.


North American Board of Certified Energy Practitioners (NABCEP) – Offers certifications and credentials for those working in the areas of photovoltaics, solar heating and small wind technologies.

Solar Energy International (SEI) - Nonprofit educational organization offering hands-on workshops and online courses in solar PV, micro-hydro and solar hot water heating.

ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers) – Offers course on Solar PV and Thermal Systems Analysis and Design focusing on cost-effective solar applications for commercial facilities.

Printed materials

NABCEP - Certified Solar Heating Installer Study and Resource Guide

California Energy Commission, Energy Research and Development Division - Solar Water Heating Assessment Project Understanding and Improving Effectiveness for California Households (2019)

Determining Property Eligibility

CSI-Thermal incentives are available for single-family residential properties, commercial and multifamily properties. To qualify for available rebates, customers must meet specific requirements.

Single-Family Residential

  • Heat their water with natural gas*
  • Install a qualifying solar water heating system
  • Are customers of one of the four designated investor-owned utilities in the state
  • Single-family customers must directly use the hot water from the solar water heating system

Please note that space heating, space cooling and swimming pool or spa heating are not eligible uses for single-family properties.

* Residential CSI-Thermal rebates are no longer available for electric- or propane-displacing systems.

Multifamily Residential & Commercial

  • Use a solar thermal system to offset natural gas consumption*
  • Install a qualifying solar thermal system
  • Are customers of one of the designated four investor-owned utilities in the state
  • Commercial and multifamily customers can receive a rebate for a solar hot water system and other solar thermal systems installed for process heat, space cooling, space heating, pool heating or any combination

Examples of rebate-eligible businesses include commercial laundries, gyms, laundromats, restaurants, convalescent homes, hotels/motels, school dormitories, prisons, agricultural processes, hospitals, food processors, wineries, breweries, car washes and other applications.

*CSI-Thermal rebate funds for electric- or propane-displacing multifamily and commercial systems within the SDG&E service territory have been exhausted, and customers using electric or propane for water heating are no longer eligible for CSI-Thermal incentives.

Permitting Requirements for Solar Thermal Systems

A permit from the local building department is required for all applications submitted to the CSI-Thermal Program. Furthermore, solar thermal systems must be rated by the Solar Rating and Certification Corporation (SRCC) or the International Association of Plumbing and Mechanical Officials (IAPMO).

  • Commercial/multifamily collectors must have OG-100 certification
  • System installations must conform to manufacturers' specifications and all applicable codes and standards
  • All systems must have freeze and overheat protection

Permitting Requirements for Pools

All solar pool heating systems also require a permit from the local building department as part of the incentive application. If a jurisdiction does not issue a building permit for solar pool heating system installations, please provide a letter from the department indicating that a permit is not required.

Please note: In Southern California, solar pool heating systems must receive a permit from the local county Department of Environmental Health and Safety.