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.


Reduce energy costs and your carbon footprint with solar thermal technologies

Please Note
The California Solar Initiative–Thermal Program began phasing out on July 31, 2020, and is no longer accepting incentive applications. It has entered a sunset phase during which projects with confirmed reservations will still be processed and paid. If you are a contractor or property owner with a project in review, refer to the Active Applicants page.

Sunlight can provide the energy to heat water for just about every need in your residence, multifamily property or business from hand washing and dish cleaning to supplying appliances and industrial equipment.

What is Solar Water Heating?

A solar water heating system captures the warmth of the sun and uses it to heat water. Unlike solar photovoltaic (PV) systems that collect sunlight and convert it into electricity, solar water heating systems simply absorb the sun’s heat and transfer it to your hot water supply. With solar water heating, you can reduce your energy consumption and utility bills without sacrificing comfort or reliability—even on cloudy days and nights, the system works with your existing water heater so that you have hot water 24/7.

How Does Solar Water Heating Work?

A solar water heating (SWH) system works in conjunction with your existing water heater or boiler to essentially preheat water before it enters the existing tank. Current systems can be used in conjunction with natural gas, electric or propane backup water heaters and boilers and even with tankless water heaters as long as the solar water heating system is compatible.

Inside Solar Thermal Systems

Solar collectors, typically mounted on your property's roof, absorb the sun's thermal energy.

A pump circulates a heat transfer fluid from the collectors through a heat exchanger in your solar storage tank.

The heat exchanger transfers the sun's warmth to your water supply.

Hot water flows to your existing water heater, which provides backup heating when the sun isn't shining.

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